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  • 1. Bakkman, L.
    et al.
    Sahlin, K.
    Holmberg, H-C.
    Tonkonogi, Michail
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Quantitative and qualitative adaptation of human skeletal muscle mitochondria to hypoxic compared to normoxic training at the same relative work rate2007In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 190, no 3, 243-251 p.Article in journal (Refereed)
    Abstract [en]

    Aim: To investigate if training during hypoxia (H) improves the adaptation of muscle oxidative function compared with normoxic (N) training performed at the same relative intensity.

    Method: Eight untrained volunteers performed one-legged cycle training during 4 weeks in a low-pressure chamber. One leg was trained under N conditions and the other leg under hypobaric hypoxia (526 mmHg) at the same relative intensity as during N (65% of maximal power output, Wmax). Muscle biopsies were taken from vastus lateralis before and after the training period. Muscle samples were analysed for the activities of oxidative enzymes [citrate synthase (CS) and cytochrome c oxidase (COX)] and mitochondrial respiratory function.

    Results: W max increased with more than 30% over the training period during both N and H. CS activity increased significantly after training during N conditions (+20.8%, P < 0.05) but remained unchanged after H training (+4.5%, ns) with a significant difference between conditions (P < 0.05 H vs. N). COX activity was not significantly changed by training and was not different between exercise conditions [+14.6 (N) vs. -2.3% (H), ns]. Maximal ADP stimulated respiration (state 3) expressed per weight of muscle tended to increase after N (+31.2%, P < 0.08) but not after H training (+3.2%, ns). No changes were found in state four respiration, respiratory control index, P/O ratio, mitochondrial Ca2+ resistance and apparent Km for oxygen.

    Conclusion: The training-induced increase in muscle oxidative function observed during N was abolished during H. Altitude training may thus be disadvantageous for adaptation of muscle oxidative function.

  • 2.
    Bellardini, Helena
    et al.
    Dalarna University, School of Health and Social Studies, Sport and Health Science.
    Henriksson, Anders
    Dalarna University, School of Health and Social Studies, Sport and Health Science.
    Tonkonogi, Michail
    Dalarna University, School of Health and Social Studies, Medical Science.
    Bra och enkla fystester2013Book (Other academic)
  • 3.
    Bellardini, Helena
    et al.
    Dalarna University, School of Health and Social Studies, Medical Science.
    Henriksson, Anders
    Dalarna University, School of Health and Social Studies, Medical Science.
    Tonkonogi, Michail
    Dalarna University, School of Health and Social Studies, Medical Science.
    Tester och mätmetoder för idrott och hälsa2009Book (Other academic)
  • 4.
    Bellardini, Helena
    et al.
    Dalarna University, School of Health and Social Studies, Medical Science.
    Knutsson, Magnus
    Dalarna University, School of Health and Social Studies, Medical Science.
    Tonkonogi, Michail
    Dalarna University, School of Health and Social Studies, Medical Science.
    Inverkan av olika farthållningsstrategier på prestationsförmåga vid kortvarigt maximalt fysiskt arbete.2006In: Svensk Idrottsforskning: Organ för Centrum för Idrottsforskning, ISSN 1103-4629, no 2, 20-26 p.Article in journal (Other academic)
  • 5.
    Bellardini, Helena
    et al.
    Dalarna University, School of Health and Social Studies, Sport and Health Science.
    Tonkonogi, Michail
    Dalarna University, School of Health and Social Studies, Medical Science.
    Senior Power - Styrketräning för äldre2013 (ed. 1)Book (Other academic)
  • 6.
    Bellardini, Helena
    et al.
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Tonkonogi, Michail
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Senior power: styrketrening for eldre2014 (ed. 1)Book (Other academic)
  • 7.
    Bellardini, Helena
    et al.
    Dalarna University, School of Health and Social Studies, Sport and Health Science.
    Tonkonogi, Michail
    Dalarna University, School of Health and Social Studies, Sport and Health Science.
    Styrketräning för barn: del 2: rekommendationer i andra länder2009In: Svensk Idrottsmedicin, ISSN 1103-7652, 13-17 p.Article in journal (Other academic)
  • 8.
    Bellardini, Helena
    et al.
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Tonkonogi, Michail
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Mckee, Kevin
    Dalarna University, School of Education, Health and Social Studies, Social Work.
    The effect of gender on strength training in older people: a Swedish population study2012In: Psychology and Health, ISSN 0887-0446, E-ISSN 1476-8321, Vol. 27, no s1, 155-156 p.Article in journal (Refereed)
    Abstract [en]

    Background: Physical exercise contributes to healthy ageing, and strength training has beenshown to improve independence in older people.

    Method: Six hundred older people wererandomly selected from the Swedish population, and sent a self-completion questionnaire(57% response rate, n¼343) examining exercise history, current strength training, andperceived benefits and barriers to strength training.

    Results: Gender was associated with aperceived positive effect of strength training on quality of life (Women 42% vs. Men 27%).The most commonly reported benefits of strength training were better mobility (71%), energy(70%), and muscle strength (69%), with most benefits endorsed more commonly by womenthan men. The most commonly reported barriers to strength training were believing otherforms of exercise more suitable (49%) and cost (20%; Women 31% vs. Men 13%).

    Discussion:To better promote healthy ageing, interventions should be embedded in an understanding ofthe effect of gender on exercise behaviour.

  • 9. Bishop, David J.
    et al.
    Thomas, Claire
    Moore-Morris, Tom
    Tonkonogi, Michail
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Sahlin, Kent
    Mercier, Jacques
    Sodium bicarbonate ingestion prior to training improves mitochondrial adaptations in rats2010In: American Journal of Physiology. Endocrinology and Metabolism, ISSN 0193-1849, E-ISSN 1522-1555, Vol. 299, no 2, E225-E233 p.Article in journal (Refereed)
    Abstract [en]

    We tested the hypothesis that reducing hydrogen ion accumulation during training would result in greater improvements in muscle oxidative capacity and time to exhaustion (TTE). Male Wistar rats were randomly assigned to one of three groups (CON, PLA, and BIC). CON served as a sedentary control, whereas PLA ingested water and BIC ingested sodium bicarbonate 30 min prior to every training session. Training consisted of seven to twelve 2-min intervals performed five times/wk for 5 wk. Following training, TTE was significantly greater in BIC (81.2 +/- 24.7 min) compared with PLA (53.5 +/- 30.4 min), and TTE for both groups was greater than CON (6.5 +/- 2.5 min). Fiber respiration was determined in the soleus (SOL) and extensor digitorum longus (EDL), with either pyruvate (Pyr) or palmitoyl carnitine (PC) as substrates. Compared with CON (14.3 +/- 2.6 nmol O(2).min(-1).mg dry wt(-1)), there was a significantly greater SOL-Pyr state 3 respiration in both PLA (19.6 +/- 3.0 nmol O(2).min(-1).mg dry wt(-1)) and BIC (24.4 +/- 2.8 nmol O(2).min(-1).mg dry wt(-1)), with a significantly greater value in BIC. However, state 3 respiration was significantly lower in the EDL from both trained groups compared with CON. These differences remained significant in the SOL, but not the EDL, when respiration was corrected for citrate synthase activity (an indicator of mitochondrial mass). These novel findings suggest that reducing muscle hydrogen ion accumulation during running training is associated with greater improvements in both mitochondrial mass and mitochondrial respiration in the soleus.

  • 10.
    Carlsson, Magnus
    et al.
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Carlsson, Tomas
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Hammarström, Daniel
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Granath, Johan
    Regional Sports Federation of Dalarna.
    Westergren, Jens
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Malm, Christer
    Idrottsmedicin, Umeå Universitet.
    Tonkonogi, Michail
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Validation of off-season physiological tests with ski ranking in elite male junior cross-country skiing2012In: Book of Abstract: Supplement to Medicine and Science in Sports and Exercise, Volume 44, Number 5, May 2012, 2012, 353-353 p.Conference paper (Refereed)
  • 11.
    Carlsson, Magnus
    et al.
    Dalarna University, School of Education, Health and Social Studies, Medical Science.
    Carlsson, Tomas
    Dalarna University, School of Education, Health and Social Studies, Medical Science.
    Hammarström, Daniel
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Granath, Johan
    Westergren, Jens
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Malm, Christer
    Tonkonogi, Michail
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Validation of off-season physiological tests with ski ranking in elite male junior cross-country skiing2012In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 44, no s2, 516-516 p.Article in journal (Other academic)
  • 12.
    Carlsson, Magnus
    et al.
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science. Sports Medicine Unit, Umeå University, Umeå, Sweden, Dala Sports Academy, Falun, Sweden.
    Carlsson, Tomas
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science. Sports Medicine Unit, Umeå University, Umeå, Sweden, Dala Sports Academy, Falun, Sweden.
    Hammarström, Daniel
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science. Lillehammer University College, Lillehammer, Norway.
    Malm, Christer
    Sports Medicine Unit, Umeå University, Umeå, Sweden.
    Tonkonogi, Michail
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Prediction of race performance of elite cross-country skiers by lean mass2014In: International Journal of Sports Physiology and Performance, ISSN 1555-0265, Vol. 9, no 6, 1040-1045 p.Article in journal (Refereed)
    Abstract [en]

    Purpose: To investigate the relationship between race performance and lean mass (LM) variables, as well as to examine sex differences in body composition in elite-standard cross-country skiers. 

    Methods: Thirty-four elite cross-country skiers (18 men and 16 women) underwent a dual-emission x-ray absorptiometry body composition test to determine LM, fat mass, and bone mineral content. For both sexes, performance data were collected from a sprint prologue and a distance race. 

    Results: The absolute expression of LM variables [whole body (LMWB), upper body (LMUB), and lower body (LMLB)] was significantly correlated with finishing time in the sprint prologue independent of sex. Distance-race performance was significantly related to LMWB, LMUB, and LMLB in women; however, no correlation was found in men. Men had a significantly higher LM and lower fat mass, independent of expression (absolute or relative), for the whole body, arms, trunk, and legs, except for the absolute fat mass in the trunk. 

    Conclusions: The absolute expressions of LMWB, LMUB, and LMLB were significant predictors of sprint-prologue performance in both sexes, as well as of distance-race performance in women only. Compared with women, male skiers have a higher LM in the body segments that are major contributors to propelling forces. These results suggest that muscle mass in the lower and upper body is equally important for race performance; thus, more focus of elite skiers’ training should be directed to increasing whole-body muscle mass to improve their competitive performance capability.

  • 13.
    Carlsson, Magnus
    et al.
    Dalarna University, School of Education, Health and Social Studies, Medical Science.
    Carlsson, Tomas
    Dalarna University, School of Education, Health and Social Studies, Medical Science.
    Hammarström, Daniel
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Malm, Christer
    Tonkonogi, Michail
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Time trials predict the competitive performance capacity of junior cross-country skiers2014In: International Journal of Sports Physiology and Performance, ISSN 1555-0265, Vol. 9, no 1, 12-18 p.Article in journal (Refereed)
    Abstract [en]

    Purpose: This study investigated whether there is a correlation between time-trial performance and competitive performance capacity of male and female junior cross-country skiers and sought to explain sex-specific competitive performance capacity through multiple-regression modeling.

    Methods: The International Ski Federation's (FIS) junior ranking points for distance (FISdist) and sprint (FISsprint) competitions were used as performance parameters. A total of 38 elite junior (age 18.5 +/- 1.0 y) cross-country skiers (24 men and 14 women) completed 3 time-trial tests: a 3-km level-running time trial (TTRun), a 2-km moderate uphill (1.2 slope) roller-skiing time trial using the double-poling technique (TTDP), and a 2-km uphill (2.8 slope) roller-skiing time trial using the diagonal-stride technique (TTDiag). The correlations were investigated using Pearson correlation analysis, and regression models were created using multiple-linear-regression analysis. Results: For men, FISsprint and FISdist were correlated with the times for TTRun, TTDP, and TTDiag (all P < .001). For women, FISsprint was correlated with the times for TTRun (P < .05), TTDP (P < .01), and TTDiag (P < .01), whereas FISdist was correlated only with the times for TTDP (P < .01) and TTDiag (P < .05). The models developed for FISdist and FISsprint explained 73.9-82.3% of the variance in the performance capacity of male junior cross-country skiers. No statistically valid regression model was found for the women.

    Conclusions: Running and roller-skiing time trials are useful tests for accurately predicting the performance capacity of junior cross-country skiers.

  • 14.
    Carlsson, Magnus
    et al.
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Carlsson, Tomas
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Hammarström, Daniel
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Tiivel, Toomas
    Malm, Christer
    Tonkonogi, Michail
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Validation of physiological tests in relation to competitive performances in elite male distance cross-country skiing2012In: Journal of Strength and Conditioning Research, ISSN 1064-8011, E-ISSN 1533-4287, Vol. 26, no 6, 1496-1504 p.Article in journal (Refereed)
    Abstract [en]

    The purpose of the present study was to establish which physiological test parameters reflects the distance performances in the Swedish National Championships in cross-country skiing (SNC) and the International Ski Federation's ranking points for distance performances (FISdist). The present study also aimed to create multiple regression models to describe skiing performance for the SNC distance races and International Ski Federation's (FIS) ranking. Twelve male, Swedish, national elite, cross-country skiers (maximal oxygen consumption [(V) over dotO(2)max] = 5.34 +/- 0.34 L.min(-1)) volunteered to participate in the study. Their results in the 2008 SNC (15 km race [SNC15] and 30 km race [SNC30]) and FISdist points were used as performance data. On the week preceding the Championship, subjects completed a test battery consisting of 7 physiological tests: isokinetic knee extension peak torque (PT), vertical jumps (VJ), lactate threshold (LT), (V) over dotO(2)max, and 3 double poling tests of different durations (DP20, DP60, and DP360). Correlations were established using Pearson's correlation analysis, and models to describe skiing performance were created using standard multiple linear regression analysis. Significant correlations were found between the performance parameters and test parameters derived from LT, (V) over dotO(2)max, and DP60 tests. No correlations with any performance parameter were found for PT, VJ, DP20, and DP360 tests. For FISdist and SNC15, the models explain 81% and 78% of the variance in performance, respectively. No statistically valid regression model was found for SNC30. The results of this study imply that the physiological demands in male elite distance cross-country skiing performances are different in different events. To adequately evaluate a skier's performance ability in distance cross-country skiing, it is necessary to use test parameters and regression models that reflect the specific performance.

  • 15.
    Carlsson, Magnus
    et al.
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science. Sports Medicine Unit, Umeå University, Umeå, Sweden; Dala Sports Academy, Falun, Sweden.
    Carlsson, Tomas
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science. Sports Medicine Unit, Umeå University, Umeå, Sweden; Dala Sports Academy, Falun, Sweden.
    Knutsson, Magnus
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science. Dala Sports Academy, Falun, Sweden.
    Malm, Christer
    Sports Medicine Unit, Umeå University, Umeå, Sweden; Winternet, Boden, Sweden .
    Tonkonogi, Michail
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Oxygen uptake at different intensities and sub‑techniques predicts sprint performance in elite male cross‑country skiers2014In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 114, no 12, 2587-2595 p.Article in journal (Refereed)
    Abstract [en]

    Purpose. To investigate the relationship between sprint-prologue performance (using the classical technique) and the oxygen uptake at the lactate threshold ( V˙O2obla), maximal oxygen uptake ( V˙O 2max), and mean oxygen uptake during double poling ( V˙O 2dp).

    Methods. Eight elite male cross-country skiers [age 24.8 ± 4.8 years, (mean ± SD)] completed two treadmill roller-skiing tests using the diagonal-stride technique and a 60 s double-poling test on a ski-ergometer to determine their V˙O2obla, V˙O 2max, and V˙O 2dp. Performance data were generated from a 1.25 km sprint prologue. Power-function modelling was used to predict the skiers’ race speeds based on the oxygen-uptake variables and body mass.

    Results. There were correlations between the race speed and the absolute expression of the V˙O2obla (r = 0.79, P = 0.021), V˙O 2max (r = 0.86, P = 0.0069), and V˙O 2dp (r = 0.94, P = 0.00062). The following power-function models were established for race-speed prediction: 1.09 · V˙O 2obla0.21, 1.05 · V˙O 2max0.21, and 1.19 · V˙O 2dp0.20; these models explained 60 % (P = 0.024), 73 % (P = 0.0073), and 87 % (P = 0.00073), respectively, of the variance in the race speed. However, body mass did not contribute to any of the models (P = 0.97, 0.88, and 0.21, respectively).

    Conclusions. Oxygen uptake at different intensities and sub-techniques is an indicator of elite male sprint-prologue performance. The absolute expression of the investigated oxygen-uptake variables should be used when evaluating elite male sprint-prologue performances; if skiers oxygen uptake differs by 1 %, their performances will likely differ by 0.2 % in favour of the skier with higher oxygen uptake.

  • 16.
    Carlsson, Magnus
    et al.
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Carlsson, Tomas
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Olsson, Mats
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Brorsson, Sofia
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Malm, Christer
    Idrottsmedicin, Umeå Universitet.
    Tonkonogi, Michail
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Peak hand-grip force predicts competitive performance in elite female cross-country skiers2014Conference paper (Refereed)
  • 17.
    Carlsson, Magnus
    et al.
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science. Umeå universitet; Dala Sports Academy.
    Carlsson, Tomas
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science. Umeå universitet; Dala Sports Academy.
    Wedholm, Lars
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science. Dala Sports Academy.
    Nilsson, Mattias
    Regional Sports Federation of Dalarna.
    Malm, Christer
    Idrottsmedicin, Umeå Universitet.
    Tonkonogi, Michail
    Dalarna University, School of Education, Health and Social Studies, Medical Science.
    Physiological demands of competitive sprint and distance performance in elite female cross-country skiing2016In: Journal of Strength and Conditioning Research, ISSN 1064-8011, E-ISSN 1533-4287, Vol. 30, no 8, 2138-2144 p.Article in journal (Refereed)
    Abstract [en]

    The purpose was to investigate the relationship between elite females' competitive performance capability in sprint and distance cross-country skiing and the variables of gross efficiency (GE), work rate at the onset of blood-lactate accumulation (OBLA4mmol), maximal oxygen uptake (VO2max), maximal speed (Vmax), and peak upper-body oxygen uptake (VO2peak). Ten elite female cross-country skiers (age 24.5 ± 2.8 years) completed treadmill roller-skiing tests to determine GE, OBLA4mmol, and VO2max using the diagonal-stride technique as well as Vmax and VO2peak using the double-poling technique. International Ski Federations ranking points for sprint (FISsprint) and distance (FISdist) races were used as competitive performance data. There were correlations between the FISsprint and the VO2max expressed absolutely (P = 0.0040), Vmax (P = 0.012), and VO2peak expressed absolutely (P < 0.001) and as a simple ratio-standard (P = 0.049). The FISdist were correlated with OBLA4mmol (P = 0.048), VO2max expressed absolutely (L·min) (P = 0.015) and as a simple ratio-standard (P = 0.046), and VO2peak expressed absolutely (P = 0.036) and as a simple ratio-standard (mL·min·kg) (P = 0.040). The results demonstrate that the physiological abilities reflected by VO2max and VO2peak are indicators of competitive sprint and distance performance in elite female cross-country skiing. In addition, the ability to generate a high Vmax indicates the performance in sprint races whereas the skier's OBLA4mmol reflects the performance capability in distance races. Based on the results, when evaluating the performance capacity of elite female cross-country skiers, it is recommended to use physiological variables that reflect competitive performance.

  • 18.
    Carlsson, Tomas
    et al.
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Carlsson, Magnus
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Felleki, Majbritt
    Dalarna University, School of Technology and Business Studies, Statistics.
    Hammarström, Daniel
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Heil, Daniel
    Montana State University.
    Malm, Christer
    Umeå Universitet, Idrottsmedicin.
    Tonkonogi, Michail
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Scaling maximal oxygen uptake to predict performance in elite-standard men cross-country skiers2013In: Journal of Sports Sciences, ISSN 0264-0414, E-ISSN 1466-447X, Vol. 31, no 16, 1753-1760 p.Article in journal (Refereed)
    Abstract [en]

    The purpose of this study was to: 1) establish the optimal body-mass exponent for maximal oxygen uptake (O2max) to indicate performance in elite-standard men cross-country skiers; and 2) evaluate the influence of course inclination on the body-mass exponent. Twelve elite-standard men skiers completed an incremental treadmill roller-skiing test to determine O2max and performance data came from the 2008 Swedish National Championship 15-km classic-technique race. Log-transformation of power-function models was used to predict skiing speeds. The optimal models were found to be: Race speed = 7.86 · O2max · m −0.48 and Section speed = 5.96 · O2max · m −(0.38 + 0.03 · α) · e−0.003 · Δ (where m is body mass, α is the section's inclination and Δ is the altitude difference of the previous section), that explained 68% and 84% of the variance in skiing speed, respectively. A body-mass exponent of 0.48 (95% confidence interval: 0.19 to 0.77) best described O2max as an indicator of performance in elite-standard men skiers. The confidence interval did not support the use of either “1” (simple ratio-standard scaled) or “0” (absolute expression) as body-mass exponents for expressing O2max as an indicator of performance. Moreover, results suggest that course inclination increases the body-mass exponent for O2max.

  • 19.
    Carlsson, Tomas
    et al.
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Carlsson, Magnus
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Hammarström, Daniel
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Malm, Christer
    Umeå Universitet, Idrottsmedicin.
    Tonkonogi, Michail
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Scaling of upper-body power output to predict time-trial roller skiing performance2013In: Journal of Sports Sciences, ISSN 0264-0414, E-ISSN 1466-447X, Vol. 31, no 6, 582-588 p.Article in journal (Refereed)
    Abstract [en]

    The purpose of the present study was to establish the most appropriate allometric model to predict mean skiing speed during a double-poling roller skiing time-trial using scaling of upper-body power output. Forty-five Swedish junior cross-country skiers (27 men and 18 women) of national and international standard were examined. The skiers, who had a body mass (m) of 69.3 ± 8.0 kg (mean ± s), completed a 120-s double-poling test on a ski ergometer to determine their mean upper-body power output (W). Performance data were subsequently obtained from a 2-km time-trial, using the double-poling technique, to establish mean roller skiing speed. A proportional allometric model was used to predict skiing speed. The optimal model was found to be: Skiing speed = 1.057 · W 0.556 · m −0.315, which explained 58.8% of the variance in mean skiing speed (P < 0.001). The 95% confidence intervals for the scaling factors ranged from 0.391 to 0.721 for W and from −0.626 to −0.004 for m. The results in this study suggest that allometric scaling of upper-body power output is preferable for the prediction of performance of junior cross-country skiers rather than absolute expression or simple ratio-standard scaling of upper-body power output.

  • 20.
    Carlsson, Tomas
    et al.
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science. Umeå universitet.
    Carlsson, Magnus
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science. Umeå universitet.
    Hammarström, Daniel
    Lillehammer University College.
    Rønnestad, Bent R
    Lillehammer University College.
    Malm, Christer
    Umeå Universitet, Idrottsmedicin.
    Tonkonogi, Michail
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Optimal V. O2max-to-mass ratio for predicting 15 km performance among elite male cross-country skiers2015In: Open Access Journal of Sports Medicine, ISSN 1179-1543, E-ISSN 1179-1543, Vol. 6, 353-360 p.Article in journal (Refereed)
    Abstract [en]

    The aim of this study was 1) to validate the 0.5 body-mass exponent for maximal oxygen uptake (V. O2max) as the optimal predictor of performance in a 15 km classical-technique skiing competition among elite male cross-country skiers and 2) to evaluate the influence of distance covered on the body-mass exponent for V. O2max among elite male skiers. Twenty-four elite male skiers (age: 21.4±3.3 years [mean ± standard deviation]) completed an incremental treadmill roller-skiing test to determine their V. O2max. Performance data were collected from a 15 km classicaltechnique cross-country skiing competition performed on a 5 km course. Power-function modeling (ie, an allometric scaling approach) was used to establish the optimal body-mass exponent for V . O2max to predict the skiing performance. The optimal power-function models were found to be race speed = 8.83⋅(V . O2max m-0.53) 0.66 and lap speed = 5.89⋅(V . O2max m-(0.49+0.018lap)) 0.43e0.010age, which explained 69% and 81% of the variance in skiing speed, respectively. All the variables contributed to the models. Based on the validation results, it may be recommended that V. O2max divided by the square root of body mass (mL⋅min−1 ⋅kg−0.5) should be used when elite male skiers’ performance capability in 15 km classical-technique races is evaluated. Moreover, the body-mass exponent for V . O2max was demonstrated to be influenced by the distance covered, indicating that heavier skiers have a more pronounced positive pacing profile (ie, race speed gradually decreasing throughout the race) compared to that of lighter skiers.

  • 21.
    Carlsson, Tomas
    et al.
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Carlsson, Magnus
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Hammarström, Daniel
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Tonkonogi, Michail
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Scaling oxygen consumption to body mass in real elite cross-country skiing performances2009In: Book of Abstracts: Sport sciences: Nature, Nurture and Culture / [ed] Loland, S., et al., 2009, 351-352 p.Conference paper (Refereed)
    Abstract [en]

    Introduction: Which are the main physiological differences between a successful and less successful cross-country skier? To our knowledgeno previous studies have examined a real elite cross-country ski competition. Main purpose of this study was therefore to validatecommonly used test parameters to skiing time and to International Ski Federation (FIS) overall seasonal ranking points and to createmultiple regression models to predict skiing performances.Methods: Twelve highly motivated male Swedish national elite cross-country skiers completed a test battery consisting of: isokinetic kneeextensor peak torque tests at three different velocities; three different vertical jumps tests; two-part treadmill roller skiing test determininglactate markers, maximal oxygen consumption (VO2max) and time to exhaustion; 60 and 360 s double poling tests determining meanupper-body power (DP60Pmean) (DP360Pmean) and mean oxygen consumption (DP60VO2mean) (DP360VO2mean).Performance data were collected from the Swedish National Championship (SNC) in cross-country skiing (13-17 March 2008): 15-km withindividual start in classical technique (SNC15); 30-km double pursuit with mass-start (SNC30); sprint prolog in free-style technique(SNCsprint). In addition to ski races, overall seasonal ski ranking points were collected from FIS 3rd Cross-Country Points List 2007/2008published before SNC for distance (FISdist) and sprint (FISsprint) races.Correlations between test parameters and performance data were established using Pearson´s correlation analysis. Prediction modelswere created using standard multiple linear regression analysis.Results: Time to exhaustion during the incremental treadmill roller ski test is best correlated with both SNC15 (r = -0.86, p < 0.001) andSNC30 (r = -0.81, p < 0.01). For SNC15 significant correlations were shown with VO2max both absolute and relative to body weight, lactatemarkers, DP60Pmean and DP60VO2mean. Corresponding correlations for SNC30 were: lactate markers, DP60VO2mean and percentagedecrease in mean knee extension peak torque when comparing highest and lowest velocities. Highest correlation coefficient forSNCsprint was found for DP60Pmean (r = -0.93, p < 0.05). Significant correlations for SNCsprint was also detected for DP360Pmean aswell as DP360VO2mean and jump height in squat jump.Prediction models explain 68, 91, 68, 77 and 82% of the variance in performance for SNC15, SNC30, SNCsprint, FISdist and FISsprint,respectively.Discussion: Correlations found in this study have validated several commonly used physiological tests with real elite cross-country skiingperformances. Frequently investigated test parameters like VO2max and anaerobic thresholds are of great importance for success incross-country skiing. Many recent research studies have focused on upper-body capacity and we could confirm that high mean powerproduction in double poling is necessary to be successful as elite skier in both sprint and distance races.

  • 22.
    Carlsson, Tomas
    et al.
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Carlsson, Magnus
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Rønnestad, Bent
    Lillehammer University College.
    Hammarström, Daniel
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Malm, Christer
    Umeå Universitet, Idrottsmedicin.
    Tonkonogi, Michail
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    The importance of scaling VO2MAX to predict cross-country skiing performance2013Conference paper (Refereed)
    Abstract [en]

    Introduction A high maximal oxygen uptake (VO2max) is of importance for success in elite male competitive distance cross-country skiing (Carlsson et al. 2012). However, it is still debatable how VO2max should be expressed to best indicate skiing performance. Therefore, the purpose of this study was to establish the optimal body mass exponent for VO2max to indicate performance in elite-standard male cross-country skiers. Methods Twenty-four elite-standard male cross-country skiers completed an incremental treadmill roller skiing test in diagonal stride technique determining VO2max. Performance data was compiled from a 15-km classic technique race. To predict performance a log-transformation of power-function model: Race speed = β0 • VO2max^β1 • m^β2 was used, where β0 to β2 are constants, and m is body mass. Statistical analyses used R version 2.13.2 (R Development Core Team, New Zeeland) and alpha was 0.05. Results Participants’ VO2max was 5.39 ± 0.57 l/min (mean ± s) and m was 75.5 ± 6.3 kg. Mean race speed was 5.83 ± 0.41 m/s. The model that best predicted performance was: Race speed = 8.829 • VO2max^0.663 • m^-0.355 = 8.829 • (VO2max • m^–0.535 )^0.663, that explains 69.2% of the variance in race speed for the 15-km classic technique race (P < 0.001). For the VO2max-to-mass ratio within the model, the 95% confidence interval (CI) for the body-mass exponent ranged from -0.947 to -0.122. Discussion The optimal body mass exponent for VO2max to indicate performance in elite-standard male cross-country skiers was -0.535. Moreover, the CI for the body-mass exponent does not support the use of simple ratio-standard scaling and absolute expression of VO2max as indicators of 15 km classic ski racing performance in elite-standard men skiers. 

  • 23.
    Carlsson, Tomas
    et al.
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Tonkonogi, Michail
    Dalarna University, School of Education, Health and Social Studies, Medical Science.
    Carlsson, Magnus
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Aerobic power and lean mass are indicators of competitive sprint performance among elite female cross-country skiers2016In: Open Access Journal of Sports Medicine, ISSN 1179-1543, E-ISSN 1179-1543, Vol. 7, 153-160 p.Article in journal (Refereed)
    Abstract [en]

    The purpose of this study was to establish the optimal allometric models to predict International Ski Federation’s ski-ranking points for sprint competitions (FISsprint) among elite female cross-country skiers based on maximal oxygen uptake (V̇O2max) and lean mass (LM). Ten elite female cross-country skiers (age: 24.5±2.8 years [mean ± SD]) completed a treadmill roller-skiing test to determine V̇O2max (ie, aerobic power) using the diagonal stride technique, whereas LM (ie, a surrogate indicator of anaerobic capacity) was determined by dual-emission X-ray anthropometry. The subjects’ FISsprint were used as competitive performance measures. Power function modeling was used to predict the skiers’ FISsprint based on V̇O2max, LM, and body mass. The subjects’ test and performance data were as follows: V̇O2max, 4.0±0.3 L min-1; LM, 48.9±4.4 kg; body mass, 64.0±5.2 kg; and FISsprint, 116.4±59.6 points. The following power function models were established for the prediction of FISsprint: 3.91×105 ∙ VO -6.002maxand 6.95×1010 ∙ LM-5.25; these models explained 66% (P=0.0043) and 52% (P=0.019), respectively, of the variance in the FISsprint. Body mass failed to contribute to both models; hence, the models are based on V̇O2max and LM expressed absolutely. The results demonstrate that the physiological variables that reflect aerobic power and anaerobic capacity are important indicators of competitive sprint performance among elite female skiers. To accurately indicate performance capability among elite female skiers, the presented power function models should be used. Skiers whose V̇O2max differs by 1% will differ in their FISsprint by 5.8%, whereas the corresponding 1% difference in LM is related to an FISsprint difference of 5.1%, where both differences are in favor of the skier with higher V̇O2max or LM. It is recommended that coaches use the absolute expression of these variables to monitor skiers’ performance-related training adaptations linked to changes in aerobic power and anaerobic capacity.

  • 24. Cotgreave, Ian
    et al.
    Goldschmidt, Lina
    Tonkonogi, Michail
    Dalarna University, School of Health and Social Studies, Medical Science.
    Svensson, Michael
    Differentiation-specific alterations to glutathione synthesis in and hormonally-stimulated release from human skeletal muscle cells.2002In: The FASEB Journal, ISSN 0892-6638, E-ISSN 1530-6860, Vol. 16, 435-437 p.Article in journal (Refereed)
  • 25. Fernstrom, M.
    et al.
    Bakkman, L.
    Tonkonogi, Michail
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Shabalina, I.
    Rozhdestvenskaya, Z.
    Mattson, C
    Enqvist, J.
    Ekblom, B.
    Sahlin, K.
    Reduced efficiency, but increased fat oxidation in mitochondria from human skeletal muscle after 24 hours ultra-endurance exercise2007In: Journal of applied physiology, ISSN 8750-7587, E-ISSN 1522-1601, Vol. 102, no 5, 1844-1849 p.Article in journal (Refereed)
    Abstract [en]

    The hypothesis that ultraendurance exercise influences muscle mitochondrial function has been investigated. Athletes in ultraendurance performance performed running, kayaking, and cycling at 60% of their peak O2 consumption for 24 h. Muscle biopsies were taken preexercise (Pre-Ex), postexercise (Post-Ex), and after 28 h of recovery (Rec). Respiration was analyzed in isolated mitochondria during state 3 (coupled to ATP synthesis) and state 4 (noncoupled respiration), with fatty acids alone [palmitoyl carnitine (PC)] or together with pyruvate (Pyr). Electron transport chain activity was measured with NADH in permeabilized mitochondria. State 3 respiration with PC increased Post-Ex by 39 and 41% (P < 0.05) when related to mitochondrial protein and to electron transport chain activity, respectively. State 3 respiration with Pyr was not changed (P > 0.05). State 4 respiration with PC increased Post-Ex but was lower than Pre-Ex at Rec (P < 0.05 vs. Pre-Ex). Mitochondrial efficiency [amount of added ADP divided by oxygen consumed during state 3 (P/O ratio)] decreased Post-Ex by 9 and 6% (P < 0.05) with PC and PC + Pyr, respectively. P/O ratio remained reduced at Rec. Muscle uncoupling protein 3, measured with Western blotting, was not changed Post-Ex but tended to decrease at Rec (P = 0.07 vs. Pre-Ex). In conclusion, extreme endurance exercise decreases mitochondrial efficiency. This will increase oxygen demand and may partly explain the observed elevation in whole body oxygen consumption during standardized exercise (+13%). The increased mitochondrial capacity for PC oxidation indicates plasticity in substrate oxidation at the mitochondrial level, which may be of advantage during prolonged exercise.

  • 26. Fernstrom, M.
    et al.
    Shabalina, I.
    Bakkman, L.
    Tonkonogi, Michail
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Mattsson, M. C.
    Enqvist, J. K.
    Ekblom, B.
    Sahlin, K.
    Skeletal muscle mitochondrial function and ROS production in response to extreme endurance exercise in athletes2006In: Biochimica et Biophysica Acta - Bioenergetics, ISSN 0005-2728, E-ISSN 1879-2650, 413-414 p.Article in journal (Other academic)
  • 27. Fernström, Maria
    et al.
    Tonkonogi, Michail
    Dalarna University, School of Health and Social Studies, Medical Science.
    Sahlin, Kent
    Effects of acute and chronic exercise on mitochondrial uncoupling in human skeletal muscle2004In: Journal of Physiology, ISSN 0022-3751, E-ISSN 1469-7793, Vol. 554, no 3, 755-763 p.Article in journal (Refereed)
    Abstract [en]

    Mitochondrial proteins such as uncoupling protein 3 (UCP3) and adenine nucleotide translocase (ANT) may mediate back-leakage of protons and serve as uncouplers of oxidative phosphorylation. We hypothesized that UCP3 and ANT increase after prolonged exercise and/or endurance training, resulting in increased uncoupled respiration (UCR). Subjects were investigated with muscle biopsies before and after acute exercise (75 min of cycling at 70% of ) or 6 weeks endurance training. Mitochondria were isolated and respiration measured in the absence (UCR or state 4) and presence of ADP (coupled respiration or state 3). Protein expression of UCP3 and ANT was measured with Western blotting. After endurance training , citrate synthase activity (CS), state 3 respiration and ANT increased by 24, 47, 40 and 95%, respectively (all P< 0.05), whereas UCP3 remained unchanged. When expressed per unit of CS (a marker of mitochondrial volume) UCP3 and UCR decreased by 54% and 18%(P < 0.05). CS increased by 43% after acute exercise and remained elevated after 3 h of recovery (P < 0.05), whereas the other muscle parameters remained unchanged. An intriguing finding was that acute exercise reversibly enhanced the capacity of mitochondria to accumulate Ca2+(P < 0.05) before opening of permeability transition pores. In conclusion, UCP3 protein and UCR decrease after endurance training when related to mitochondrial volume. These changes may prevent excessive basal thermogenesis. Acute exercise enhances mitochondrial resistance to Ca2+ overload but does not influence UCR or protein expression of UCP3 and ANT. The increased Ca2+ resistance may prevent mitochondrial degradation and the mechanism needs to be further explored.

  • 28.
    Hawke, Emma
    et al.
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Hammarström, Daniel
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Sahlin, K
    GIH, Sweden.
    Tonkonogi, Michail
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Does six-weeks of high-intensity cycle training with induced changes in acid-base balance lead to mitochondrial adaptations?2014Conference paper (Refereed)
  • 29.
    Hawke, Emma
    et al.
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Hammarström, Daniel
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Sahlin, Kent
    GIH, Sweden.
    Tonkonogi, Michail
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Effects of induced changes in acid-base balance on mitochondrial adaptations to training2014In: Book of Abstracts of the 19th annual congress of the European College of Sport Science – ECSS Amsterdam 2014, European College of Sport Science, 2014Conference paper (Refereed)
    Abstract [en]

    Introduction

    Endurance training leads to an improved ability of muscle to utilize oxygen. This is related to an increased density and function of mitochondria. The biogenesis and adaptation of mitochondria is a complex process mediated by various signalling pathways and seems to be highly sensitive to the type of exercise and the local environment in the muscle. Changes in the muslce environment in terms of altered metabolism and substrate accumulation are affected by changes in acid/base balance in response to exercise. Recent studies have shown that changes in acid/base balance may affect the regulation of mitochondrial adaptation to acute exercise; however, how this responds to training and relates to performance adaptations in humans is unclear. Similarly, the effect of acid/base balance on mechanisms underlying mitochondrial biogenesis is unclear. The objectives of this study were to examine the relationship between acid/base balance, mitochondrial biogenesis and adaptation.

    Methods

    Nineteen recreationally active men undertook a six-week periodised high-intensity interval training programme, a protocol known to produce increases in mitochondrial biogenesis. Participants were matched for aerobic fitness and randomly assigned to one of two different training groups. One group ingested sodium bicarbonate (alkaline) and the other group ingested a placebo prior to each training session. Performance test results, blood samples and muscle biopsies were collected before and after the six week training period and assessed for changes in aerobic fitness, blood metabolites and muscle markers of mitochondrial function and biogenesis. Changes in gene expression associated with mitochondrial biogenesis were also examined. 

    Results

    After the training period, there were significant (P < 0.05) improvements in TTF, Wmax and LT in both groups, citrate synthase activity in the alkaline group and VO2peak in the placebo group. Improvements were also seen in citrate synthase activity in the placebo group and VO2peak in the alkaline group, however these did not reach significance (P = 0.089 and 0.066 respectively).Despite these significant changes within groups in response to training, there were no significant differences between groups.

    Discussion

    Both training groups showed substantial changes in performance and physiological measures following the training period, however, suppressing exercise-induced acidosis during training did not significantly improve mitochondrial adaptations or performance in comparison to the placebo condition. However, there was a large degree of individual variation in the response and there were trends towards greater adaptations when exercise-induced acidosis was attenuated.

  • 30. Lindberg, A-S
    et al.
    Malm, C.
    Hammarström, Daniel
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Oksa, J.
    Tonkonogi, Michail
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Maximal work capacity and performance depends warm-up procedure and environmental but not inspired air temperatures2012In: Journal of Exercise Physiology - Online, ISSN 1097-9751, E-ISSN 1097-9751, Vol. 15, no 1, 26-39 p.Article in journal (Refereed)
    Abstract [en]

    The purpose of this study was to compare peak (VO 2 peak) and maximal (VO 2 max) oxygen uptake, physical performance, and lactate accumulation [la-] in warm versus cold environments. The influence of inhaled air temperature and different warm up modes on these variables as well as arterial oxygen saturation (SaO 2%) and pulmonary function were also studied. Two studies were performed. In study A, 10 males performed maximal exercise tests on a bicycle at +20°C and -12°C. In study B, 8 elite cross-country skiers performed maximal cross-country skiing tests at +13.7°C. Different warm up modes (continuous and intermittent) and different temperatures of the inhaled air (-8°C and +13°C) were used. In study A, we found significantly higher VO 2 peak, peak carbon dioxide (VCO 2 peak), peak ventilation (V E peak) and respiratory exchange ratio (RER) in +20°C compared to -12°C. In study B, we found significantly lower SaO 2% at the end compared to the beginning of the maximal performance test. Time to exhaustion (T ex) was significantly longer using intermittent warm up irrespectively of inhaled air temperature. In conclusion, we found that VO 2 max was affected by different environmental temperatures but not by different temperatures of the inhaled air and that intermittent warm up increased T ex without affecting VO 2 max.

  • 31. Lupo, Corrado
    et al.
    Guidotti, Flavia
    Goncalves, Carlos E.
    Moreira, Liliana
    Doupona Topic, Mojca
    Bellardini, Helena
    Dalarna University, School of Education, Health and Social Studies, Sport and Health Science.
    Tonkonogi, Michail
    Dalarna University, School of Education, Health and Social Studies, Medical Science.
    Colin, Allen
    Capranica, Laura
    Motivation towards dual career of European student-athletes2015In: European Journal of Sport Science, ISSN 1746-1391, E-ISSN 1536-7290, Vol. 15, no 2, 151-160 p.Article in journal (Refereed)
    Abstract [en]

    The present study aimed to investigate motivations for the dual career of European student-athletes living in countries providing different educational services for elite athletes: State-centric regulation–State as sponsor/facilitator (State), National Sporting Federations/Institutes as intermediary (Federation) and Laisser Faire, no formal structures (No Structure). Therefore, the European Student-athletes’ Motivation towards Sports and Academics Questionnaire (SAMSAQ-EU) was administered to 524 European student-athletes. Exploratory Factor Analysis, and Confirmatory Factor Analysis were applied to test the factor structure, and the reliability and validity of the SAMSAQ-EU, respectively. A multivariate approach was applied to verify subgroup effects (P ≤ 0.05) according to gender (i.e., female and male), age (i.e., ≤24 years, >24 years), type of sport (i.e., individual sport and team sport) and competition level (i.e., national and international). Insufficient confirmatory indexes were reported for the whole European student-athlete group, whereas distinct three factor models [i.e., Student Athletic Motivation (SAM); Academic Motivation (AM); Career Athletic Motivation (CAM)] emerged, with acceptable reliability estimates, for State (SAM = 0.82; AM = 0.75; and CAM = 0.75), Federation (SAM = 0.82; AM = 0.66; and CAM = 0.87) and No Structure (SAM = 0.78; AM = 0.74; and CAM = 0.79) subgroups. Differences between subgroups were found only for competition level (P < 0.001) in relation to SAM (P = 0.001) and CAM (P < 0.001). For SAM, the highest and lowest values emerged for Federation (national, 5.1 ± 0.5; international, 5.4 ± 0.5) and State (national, 4.5 ± 0.9; international, 4.8 ± 0.7). The opposite picture emerged for CAM (Federation: national, 3.3 ± 0.7; international, 3.5 ± 0.9; State: national, 5.0 ± 0.8; international, 5.0 ± 0.9). Therefore, despite SAMSAQ-EU demonstrated to be a useful tool, results showed that European student-athletes’ motivation for dual career has to be specifically investigated according to social contexts.

  • 32. Röijezon, Ulrik
    et al.
    Løvoll, Grunde
    Henriksson, Anders
    Tonkonogi, Michail
    Dalarna University, School of Education, Health and Social Studies, Medical Science.
    Lehto, Niklas
    An initial study on the coordination of rod and line hauling movements in distance fly casting2017In: Annals of Applied Sport Science, ISSN 2322-4479Article in journal (Refereed)
    Abstract [en]

    Background. The double haul is a unique feature of single-handed fly casting and is used in both fly fishing and fly casting competition. The movement behaviour during the double haul has not been investigated in previous research.

    Objectives. Describe the coordination of the rod and line hauling movements during distance fly casting.

    Methods. Elite fly casters performed distance casting with four different fly rod and fly line set-ups used in fly fishing and fly casting competition. Rod and hauling movements were measured with a 3D motion analysis system.

    Results. The rod and line hauling movements were coordinated in an order whereby peak translational speed of the rod occurs prior to the peak speed of the angular rotation of the rod, and the peak speed of the angular rotation of the rod occurs prior to the peak speed of the line haul. This was consistent for all cast sequences, i.e., the back and forward false casts and the delivery cast, and for all four equipment set-ups, i.e., a shooting-head line cast with a relatively stiff fly rod and a long-belly line cast with three different fly rods with different stiffness and action curves. Results also showed differences in movement coordination between cast sequences and rod and line set-ups.

    Conclusion. Among elite casters, single-handed fly casting with double haul is coordinated in an order of events whereby the peak speed occurs first for the translation of the rod, then for the rotation of the rod and finally for the line haul.

  • 33. Sahlin, K
    et al.
    Sallstedt, E-K
    Bishop, D
    Tonkonogi, Michail
    Dalarna University, School of Education, Health and Social Studies, Medical Science.
    Turning down lipid oxidation during heavy exercise--what is the mechanism?2008In: Journal of Physiology and Pharmacology, ISSN 0867-5910, Vol. 59, no 4, 19-30 p.Article in journal (Refereed)
    Abstract [en]

    A high potential for lipid oxidation is a sign of metabolic fitness and is important not only for exercise performance but also for health promotion. Despite considerable progress during recent years, our understanding of how lipid oxidation is controlled remains unclear. The rate of lipid oxidation reaches a peak at 50-60% of (V) over dotO(2) (max) after which the contribution of lipids decreases both in relative and absolute terms. In the high-intensity domain (> 60% (V) over dotO(2 max)), there is a pronounced decrease in energy state, which will stimulate the glycolytic rate in excess of the substrate requirements of mitochondrial oxidative processes. Accumulation of glycolytic products will impair lipid oxidation through an interaction with the carnitine-mediated transfer of FA into mitochondria. Another potential site of control is Acyl-CoA synthetase (ACS), which is the initial step in FA catabolism. The activity of ACS may be under control of CoASH and energy state. There is evidence that additional control points exist beyond mitochondrial influx of fatty acids. The electron transport chain (ETC) with associated feed-back control by redox state is one suggested candidate. In this review it is suggested that the control of FA oxidation during heavy exercise is distributed between ACS, CPT1, and ETC.

  • 34. Sahlin, K
    et al.
    Shabalina, I
    Mattsson, M
    Bakkman, L
    Fernström, M
    Rozhdestvenskaya, Z
    Enqvist, J
    Nedergaard, J
    Ekblom, B
    Tonkonogi, Michail
    Dalarna University, School of Education, Health and Social Studies, Medical Science.
    Ultraendurance exercise increases the production of reactive oxygen species in isolated mitochondria from human skeletal muscle2010In: Journal of applied physiology, ISSN 8750-7587, E-ISSN 1522-1601, Vol. 108, no 4, 780-787 p.Article in journal (Refereed)
    Abstract [en]

    Exercise-induced oxidative stress is important for the muscular adaptation to training but may also cause muscle damage. We hypothesized that prolonged exercise would increase mitochondrial production of reactive oxygen species (ROS) measured in vitro and that this correlates with oxidative damage. Eight male athletes (24–32 yr) performed ultraendurance exercise (kayaking/running/cycling) with an average work intensity of 55% V?O2peak for 24 h. Muscle biopsies were taken from vastus lateralis before exercise, immediately after exercise, and after 28 h of recovery. The production of H2O2 was measured fluorometrically in isolated mitochondria with the Amplex red and peroxidase system. Succinate-supported mitochondrial H2O2 production was significantly increased after exercise (73% higher, P = 0.025) but restored to the initial level at recovery. Plasma level of free fatty acids (FFA) increased fourfold and exceeded 1.2 mmol/l during the last 6 h of exercise. Plasma FFA at the end of exercise was significantly correlated to mitochondrial ROS production (r = 0.74, P < 0.05). Mitochondrial content of 4-hydroxy-nonenal-adducts (a marker of oxidative damage) was increased only after recovery and was not correlated with mitochondrial ROS production. Total thiol group level and glutathione peroxidase activity were elevated after recovery. In conclusion, ultraendurance exercise increases ROS production in isolated mitochondria, but this is reversed after 28 h recovery. Mitochondrial ROS production was not correlated with oxidative damage of mitochondrial proteins, which was increased at recovery but not immediately after exercise.

  • 35. Sahlin, Kent
    et al.
    Fernström, Maria
    Tonkonogi, Michail
    Dalarna University, School of Health and Social Studies, Medical Science.
    No evidence of an intracellular lactate shuttle in rat skeletal muscle2002In: Journal of Physiology, ISSN 0022-3751, E-ISSN 1469-7793, Vol. 541, no 2, 569-574 p.Article in journal (Refereed)
    Abstract [en]

    The concerted view is that cytosolic pyruvate is transferred into mitochondria and after oxidative decarboxylation further metabolized in the tricarboxylic acid cycle. Recently this view has been challenged. Based on experimental evidence from rat skeletal muscle it has been concluded that mitochondria predominantly oxidize lactate in vivo and that this constitutes part of an 'intracellular lactate shuttle'. This view appears to be gaining acceptance in the scientific community and due to its conceptual importance, confirmation by independent experiments is required. We have repeated the experiments in mitochondria isolated from rat soleus muscle. Contrary to the previously published findings we cannot find any mitochondrial respiration with lactate. Analysis of lactate dehydrogenase (LDH) by spectrophotometry demonstrated that the activity in the mitochondrial fraction was only 0.7 % of total activity. However, even when external LDH was added to mitochondria, there were no signs of respiration with lactate. In the presence of conditions where lactate is converted to pyruvate (external additions of both LDH and NAD+), mitochondrial oxygen consumption increased. Furthermore, we provide theoretical evidence that direct mitochondrial lactate oxidation is energetically unlikely. Based on the present data we conclude that direct mitochondrial lactate oxidation does not occur in skeletal muscle. The presence of an 'intracellular lactate shuttle' can therefore be questioned.

  • 36. Sahlin, Kent
    et al.
    Nielsen, J.S.
    Mogensen, M
    Tonkonogi, Michail
    Dalarna University, School of Education, Health and Social Studies, Medical Science.
    Repeated static contractions increase mitochondrial vulnerability toward oxidative stress in human skeletal muscle.2006In: Journal of applied physiology, ISSN 8750-7587, E-ISSN 1522-1601, Vol. 101, no 3, 833-839 p.Article in journal (Other academic)
    Abstract [en]

    Repeated static contractions (RSC) induce large fluctuations in tissue oxygen tension and increase the generation of reactive oxygen species (ROS). This study investigated the effect of RSC on muscle contractility, mitochondrial respiratory function, and in vitro sarcoplasmic reticulum (SR) Ca2+ kinetics in human muscle. Ten male subjects performed five bouts of static knee extension with 10-min rest in between. Each bout of RSC (target torque 66% of maximal voluntary contraction torque) was maintained to fatigue. Muscle biopsies were taken preexercise and 0.3 and 24 h postexercise from vastus lateralis. Mitochondria were isolated and respiratory function measured after incubation with H2O2 (HPX) or control medium (Con). Mitochondrial function was not affected by RSC during Con. However, RSC exacerbated mitochondrial dysfunction during HPX, resulting in decreased respiratory control index, decreased mitochondrial efficiency (phosphorylated ADP-to-oxygen consumed ratio), and increased noncoupled respiration (HPX/Con post- vs. preexercise). SR Ca2+ uptake rate was lower 0.3 vs. 24 h postexercise, whereas SR Ca2+ release rate was unchanged. RSC resulted in long-lasting changes in muscle contractility, including reduced maximal torque, low-frequency fatigue, and faster torque relaxation. It is concluded that RSC increases mitochondrial vulnerability toward ROS, reduces SR Ca2+ uptake rate, and causes low-frequency fatigue. Although conclusive evidence is lacking, we suggest that these changes are related to increased formation of ROS during RSC.

  • 37. Sahlin, Kent
    et al.
    Söderlund, Karin
    Tonkonogi, Michail
    Dalarna University, School of Health and Social Studies, Medical Science.
    Hirakoba, Koji
    Phosphocreatine content in single fibers of human muscle after sustained submaximal exercise.1997In: American Journal of Physiology. Heart and Circulatory Physiology, ISSN 0363-6135, E-ISSN 1522-1539, Vol. 273, C172-C178 p.Article in journal (Refereed)
    Abstract [en]

    The effect of sustained submaximal exercise on muscle energetics has been studied on the single-fiber level in human skeletal muscle. Seven subjects cycled to fatigue (mean 77 min) at a work rate corresponding to approximately 75% of maximal O2 uptake. Biopsies were taken from the vastus lateralis muscle at rest, at fatigue, and after 5 min of recovery. Muscle glycogen decreased from 444 +/- 40 (SE) mmol glucosyl units/kg dry wt at rest to 94 +/- 16. Postexercise glycogen was inversely correlated (P < 0.01) to muscle content of inosine monophosphate, a catabolite of ATP. Phosphocreatine (PCr) in mixed-fiber muscle decreased at fatigue to 37% but was restored above the initial value (106.5%, P < 0.025) after 5 min of recovery. The overshoot was localized to type I fibers. The rapid reversal of PCr is in contrast to the slow recovery in contraction force. Pi increased at fatigue but less than that expected from the changes in PCr and other phosphate compounds. Mean PCr at rest was approximately 20% higher in type II than in type I fibers (86.4 +/- 3.6 and 71.6 +/- 1.8 mmol/kg dry wt, respectively, P < 0.05), but at fatigue similar PCr contents were observed in the two fiber types. Reduction in PCr in all fibers at fatigue suggests that all fibers were recruited at the end of exercise. PCr content in single fibers showed a great variability in samples at rest, exercise, and recovery. The variability was more pronounced than for ATP, and the data suggest that it is due to interfiber physiological-biochemical differences. At fatigue ATP was maintained relatively high in all single fibers, but a pronounced depletion of PCr was observed in a large number of fibers, and this may contribute to fatigue through the associated increases in Pi or/and free ADP. It is noteworthy that the increase in calculated free ADP at fatigue was similar to that after high-intensity exercise.

  • 38. Sahlin, Kent
    et al.
    Tonkonogi, Michail
    Dalarna University, School of Health and Social Studies, Medical Science.
    Söderlund, Karin
    Energy supply and muscle fatigue in humans.1998In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 162, 261-266 p.Article in journal (Refereed)
    Abstract [en]

    Limitations in energy supply is a classical hypothesis of muscle fatigue. The present paper reviews the evidence available from human studies that energy deficiency is an important factor in fatigue. The maximal rate of energy expenditure determined in skinned fibres is close to the rate of adenosine triphosphate (ATP) utilisation observed in vivo and data suggest that performance during short bursts of exercise (<5 s duration) primarily is limited by other factors than energy supply (e.g. Vmax of myosine adenosine triphosphatase (ATPase), motor unit recruitment, engaged muscle mass). Within 10 s of exercise maximal power output decreases considerably and coincides with depletion of phosphocreatine. During recovery, maximal force and power output is restored with a similar time course as the resynthesis of phosphocreatine. Increases in muscle store of phosphocreatine through dietary supplementation with creatine increases performance during high-intensity exercise. These findings support the hypothesis that energy supply limits performance during high-intensity exercise. It is well documented that pre-exercise muscle glycogen content is related to performance during moderate intensity exercise. Recent data indicates that the interfibre variation in phosphocreatine is large after prolonged exercise to fatigue and that some fibres are depleted to the same extent as after high-intensity exercise. Despite relatively small decreases in ATP, the products of ATP hydrolysis (Pi and free ADP) may increase considerably. FreeADP calculated from the creatine kinase reaction increases 10-fold both after high-intensity exercise and after prolonged exercise to fatigue. It is suggested that local increases in ADP may reach inhibitory levels for the contraction process.

  • 39. Sahlin, Kent
    et al.
    Tonkonogi, Michail
    Dalarna University, School of Health and Social Studies, Medical Science.
    Söderlund, Karin
    Plasma hypoxanthine and ammonia in humans during prolonged exercise.1999In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 80, 417-422 p.Article in journal (Refereed)
    Abstract [en]

    In this study we examined the time course of changes in the plasma concentration of oxypurines [hypoxanthine (Hx), xanthine and urate] during prolonged cycling to fatigue. Ten subjects with an estimated maximum oxygen uptake ( V?O 2max) of 54 (range 47–67) ml?·?kg -1?·?min -1 cycled at [mean?(SEM)] 74?(2)% of V?O 2max until fatigue [79?(8) min]. Plasma levels of oxypurines increased during exercise, but the magnitude and the time course varied considerably between subjects. The plasma concentration of Hx ([Hx]) was 1.3?(0.3)?µmol/l at rest and increased eight fold at fatigue. After 60?min of exercise plasma [Hx] was >10?µmol/l in four subjects, whereas in the remaining five subjects it was <5?µmol/l. The muscle contents of total adenine nucleotides (TAN?=?ATP+ADP+AMP) and inosine monophosphate (IMP) were measured before and after exercise in five subjects. Subjects with a high plasma [Hx] at fatigue also demonstrated a pronounced decrease in muscle TAN and increase in IMP. Plasma [Hx] after 60?min of exercise correlated significantly with plasma concentration of ammonia ([NH 3], r?=?0.90) and blood lactate ( r?=?0.66). Endurance, measured as time to fatigue, was inversely correlated to plasma [Hx] at 60?min ( r?=?-0.68, P?3] or blood lactate. It is concluded that during moderate-intensity exercise, plasma [Hx] increases, but to a variable extent between subjects. The present data suggest that plasma [Hx] is a marker of adenine nucleotide degradation and energetic stress during exercise. The potential use of plasma [Hx] to assess training status and to identify overtraining deserves further attention.

  • 40. Seppet, E. K.
    et al.
    Kaambre, T.
    Sikk, P.
    Tiivel, T.
    Vija, H.
    Kay, L.
    Appaix, F.
    Tonkonogi, Michail
    Dalarna University, School of Health and Social Studies, Medical Science.
    Sahlin, Kent
    Braun, U.
    Eimre, M.
    Saks, V.A.
    Functional complexes of mitochondria with MgATPase of myofibrils and sarcoplasmic reticulum in muscle cells2001In: Biochimica et Biophysica Acta - Bioenergetics, ISSN 0005-2728, E-ISSN 1879-2650, Vol. 1504, no 2-3, 379-395 p.Article in journal (Refereed)
    Abstract [en]

    Regulation of mitochondrial respiration in situ in the muscle cells was studied by using fully permeabilized muscle fibers and cardiomyocytes. The results show that the kinetics of regulation of mitochondrial respiration in situ by exogenous ADP are very different from the kinetics of its regulation by endogenous ADP. In cardiac and m. soleus fibers apparent Km for exogenous ADP in regulation of respiration was equal to 300–400 µM. However, when ADP production was initiated by intracellular ATPase reactions, the ADP concentration in the medium leveled off at about 40 µM when about 70% of maximal rate of respiration was achieved. Respiration rate maintained by intracellular ATPases was suppressed about 20–30% during exogenous trapping of ADP with excess pyruvate kinase (PK, 20 IU/ml) and phosphoenolpyruvate (PEP, 5 mM). ADP flux via the external PK+PEP system was decreased by half by activation of mitochondrial oxidative phosphorylation. Creatine (20 mM) further activated the respiration in the presence of PK+PEP. It is concluded that in oxidative muscle cells mitochondria behave as if they were incorporated into functional complexes with adjacent ADP producing systems – with the MgATPases in myofibrils and Ca,MgATPases of sarcoplasmic reticulum.

  • 41. Svensson, Michael
    et al.
    Malm, Christer
    Tonkonogi, Michail
    Dalarna University, School of Health and Social Studies, Medical Science.
    Ekblom, Björn
    Sjödin, Bertil
    Sahlin, Kent
    Effect of Q10 supplementation on tissue Q10 levels and adenine nucleotide catabolism during high-intensity exercise.1999In: Int J Sport Nutr, ISSN 1526-484X , Vol. 9, 166-180 p.Article in journal (Refereed)
    Abstract [en]

    The aim of the present study was to investigate the concentration of ubiquinone-10 (Q10), at rest, in human skeletal muscle and blood plasma before and after a period of high-intensity training with or without Q10 supplementation. Another aim was to explore whether adenine nucleotide catabolism, lipid peroxidation, and mitochondrial function were affected by Q10 treatment. Seventeen young healthy men were assigned to either a control (placebo) or a Q10-supplementation (120 mg/day) group. Q10 supplementation resulted in a significantly higher plasma Q10/total cholesterol level on Days 11 and 20 compared with Day 1. There was no significant change in the concentration of Q10 in skeletal muscle or in isolated skeletal muscle mitochondria in either group. Plasma hypoxanthine and uric acid concentrations increased markedly after each exercise test session in both groups. After the training period, the postexercise increase in plasma hypoxanthine was markedly reduced in both groups, but the response was partially reversed after the recovery period. It was concluded that Q10 supplementation increases the concentration of Q10 in plasma but not in skeletal muscle.

  • 42.
    Tonkonogi, Michail
    Dalarna University, School of Education, Health and Social Studies, Medical Science.
    Alla äldre behöver denna träning2017In: Här&Nu, ISSN 1653-2287, no 4, 13-13 p.Article in journal (Other (popular science, discussion, etc.))
  • 43.
    Tonkonogi, Michail
    Dalarna University, School of Health and Social Studies, Medical Science.
    Antioxidanter och träning: sanningar och myter2013In: Bågskytten, ISSN 0345-1216, Vol. 66, no 6, 23-25 p.Article in journal (Other (popular science, discussion, etc.))
  • 44.
    Tonkonogi, Michail
    Dalarna University, School of Health and Social Studies, Sport and Health Science.
    Att träna fettförbränning och att fettförbränningsträna är inte samma sak?2010In: Idrott och Kunskap, ISSN 1652-6961, 52-53 p.Article in journal (Other academic)
  • 45.
    Tonkonogi, Michail
    Dalarna University, School of Education, Health and Social Studies, Medical Science.
    Bästa träningen är den som blir av2017In: Här&Nu, ISSN 1653-2287, no 5, 17-17 p.Article in journal (Other (popular science, discussion, etc.))
  • 46.
    Tonkonogi, Michail
    Dalarna University, School of Health and Social Studies, Medical Science.
    Bågskytte - en precisionsidrott med höga krav på specifik styrka2014In: Bågskytten, ISSN 0345-1216, Vol. 67, no 4, 13-15 p.Article in journal (Other (popular science, discussion, etc.))
  • 47.
    Tonkonogi, Michail
    Dalarna University, School of Health and Social Studies, Sport and Health Science.
    Den aeroba nojan2011In: Idrott och Kunskap, ISSN 1652-6961, no 2, 56-57 p.Article in journal (Other (popular science, discussion, etc.))
  • 48.
    Tonkonogi, Michail
    Dalarna University, School of Health and Social Studies, Sport and Health Science.
    Hur många stulna medaljer?2012In: Idrott och Kunskap, ISSN 1652-6961, no 4, 58-59 p.Article in journal (Other (popular science, discussion, etc.))
  • 49.
    Tonkonogi, Michail
    Dalarna University, School of Health and Social Studies, Sport and Health Science.
    Hur tränar man explosiv styrka bäst?2009In: Idrott och Kunskap, ISSN 1652-6961, 52-53 p.Article in journal (Other academic)
  • 50.
    Tonkonogi, Michail
    Dalarna University, School of Education, Health and Social Studies, Medical Science.
    Idrottsmedicinen sviker barnen2012In: Svenska Dagbladet, ISSN 1101-2412, no 25 nov, 5-5 p.Article in journal (Other (popular science, discussion, etc.))
12 1 - 50 of 100
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