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Video is the most used tool for sport performance analysis as it provides a common reference point for the coach and the athlete. The problem with video is that it is a subjective tool. To overcome this, motion capture systems can used to get an objective 3D model of a person’s posture and motion, but only in laboratory settings. Unfortunately, many activities, such as most outdoor sports, cannot be captured in a lab without compromising the activity. In this paper, we propose to use an aerial drone system equipped with depth cameras, AI-based marker-less motion capture software to perform automatic skeleton tracking and real-time sports performance analysis of athletes. We experiment with off-the-shelf drone systems, miniaturized depth cameras, and commercially available skeleton tracking software to build a system for analyzing sports-related performance of athletes in their real settings. To make this a fully working system, we have conducted a few initial experiments and identified many issues that still needs to be addressed.

Objective: To investigate the relationship between head impact characteristics and the levels of blood biomarkersassociated with brain injury, neurofilament light (NfL) and glial fibrillary acidic protein (GFAP).Methods: Four elite amateur Muay Thai athletes were equipped with impact monitoring mouthguards, collectinglinear and rotational acceleration data during a period of eight weeks. Capillary blood samples were collectedafter each period of sparring sessions to analyse the levels of NfL and GFAP.Results: On a group level, mean GFAP levels were negatively correlated to mean impacts per session (p < 0.05).Two athletes had significant correlations between head impact characteristics and the levels of NfL and/or GFAP.Conclusions: The results indicate that NfL and GFAP might responded differently to linear and rotational accelerationsand/or that the effect of different types of accelerations on brain tissue integrity is individual. Themethods used could be useful to monitor brain health in different impacts sports.

The chemical digitalization of sweat using wearable sensing interfaces is an attractive alternative to traditional blood-based protocols in sports. Although sweat lactate has been claimed to be a relevant biomarker in sports, an analytically validated wearable system to prove that has not yet been developed. We present a fully integrated sweat lactate sensing system applicable to in situ perspiration analysis. The device can be conveniently worn in the skin to monitor real-time sweat lactate during sports, such as cycling and kayaking. The novelty of the system is threefold: advanced microfluidics design for sweat collection and analysis, an analytically validated lactate biosensor based on a rational design of an outer diffusion-limiting membrane, and an integrated circuit for signal processing with a custom smartphone application. The sensor covering the range expected for lactate in sweat (1-20 mM), with appropriate sensitivity (-12.5 ± 0.53 nA mM-1), shows an acceptable response time (<90 s), and the influence of changes in pH, temperature, and flow rate are neglectable. Also, the sensor is analytically suitable with regard to reversibility, resilience, and reproducibility. The sensing device is validated through a relatively high number of on-body tests performed with elite athletes cycling and kayaking in controlled environments. Correlation outcomes between sweat lactate and other physiological indicators typically accessible in sports laboratories (blood lactate, perceived exhaustion, heart rate, blood glucose, respiratory quotient) are also presented and discussed in relation to the sport performance monitoring capability of continuous sweat lactate.

This paper explores the significance of special teams, particularlypowerplay, in ice hockey. Despite the commonly held perception oftheir importance, little research has examined the impact of powerplayand penalty kill performance on overall team success. The paper usesseveral seasons of NHL data to characterize goal-scoring and manpoweropportunities, and perform analysis from several perspectives. The resultsindicate that individual even strength goals and powerplay goalshave similar value, but the larger share of even strength goals scoredover a season makes even strength play a more important contributorto team success. The paper also finds a high correlation between teamsthat perform above/below average during even strength and powerplay.This study provides valuable insights into the dynamics of ice hockeygameplay and the role of special teams in determining team success.

In the last decade, sport performance assessment has significantly transformed due to the appearance of disruptive technologies. Subjective pen and paper notations have evolved into advanced wearable sensing systems that acquire performance-related data. The selection of adequate performance metric variables always causes a debate in sport physiology, and this becomes more relevant once new biochemical indicators are proposed, such as sweat lactate. Here, we analyze the correlation of real-time sweat lactate, obtained with a validated wearable biosensor, with the typical physiological parameters often recorded in sports laboratories (e. g., blood lactate, Borg scale for the rating of perceived exertion, heart rate, power output, blood glucose, and respiratory quotient). We found that the heart rate, power output, Borg scale, and blood lactate relate to sweat lactate in independent individuals during cycling activity. Hence, we demonstrate the potential to associate non-invasive, quantitative, and personalized analysis with sport practice.

The aim of this study was to determine the impact of runs 1 and 2 on overall rank in Giant Slalom. Data from 15 seasons (2005/2006–2019/2020) including and unique starts for women (n = 2,294) and men (n = 2,328) were analyzed. Skiers were grouped based on final ranks 1–3 (G3), 4–10 (G10), and 11–20 (G20) and separately analyzed for women and men. A Wilcoxon-signed rank test was used for comparisons between runs 1 and 2, while a multi-nominal logistic regression was used to identify odds ratios (OR) associated with group rank. Women had similar run times for runs 1 and 2 (p = 0.734), while men had faster times on run 2 (p < 0.001). The strongest association to G3 was during run 1 for run time (men: OR 1.06–1.12; women: OR 1.06–1.11, all p < 0.01) and gate-to-gate times (men: OR 33–475; women: OR 81–2,301, all p < 0.001). Overall, this study demonstrates the importance of a fast first run for improving the final ranking group and the need to increase the tempo going from the first to the second run for men. Copyright © 2022 Björklund and Swarén.

This study examined the micro-pacing strategies during a distance freestyle cross-country (XC) skiing competition. Nine female and 10 male highly trained XC skiers wore a GNSS device during a FIS-sanctioned race. The course was ~4900 m; women completed two-laps; men completed three-laps. The course was divided into uphill (S1, S3, S5, S7), downhill (S2, S4, S6, S8), and flat (S9) sections for analyses. Statistical parametric mapping was used to determine the course positions (clusters) where total race time or section time was significantly associated with instantaneous skiing speed. Total race time was associated with instantaneous skiing speed during a cluster in S1 on lap 2 for both sexes (t ≥ 5.899, p ≤ 0.008). The two longest uphill sections (S1; S5) and the flat section (S9) contained clusters where section times were related to instantaneous skiing speed for both sexes (p < 0.05). The fastest woman gained 6.9 s on the slowest woman during a cluster in S1 on lap 1 and 7.3 s during a cluster in S9 on lap 1. The fastest man gained 51.7 s on the slowest man over all clusters in S5 over the 3 laps combined. Compared to skiers with longer total race times, skiers with shorter race times skied with faster instantaneous speeds in some clusters of the uphill sections, as well as on the flat section of the course. This study also identified different relative micro-pacing strategies for women and men during freestyle distance XC skiing races. Finally, statistical parametric mapping analyses can help to identify individual strengths and weaknesses for guiding training programs and optimise competition pacing strategies.

The purpose of the study was to investigate whether there are energy-efficiency differences between the execution of the old-fashioned double-poling technique (DPOLD) and the modern double-poling technique (DPMOD) at a submaximal work intensity among elite male cross-country skiers. Fifteen elite male cross-country skiers completed two 4-min tests at a constant mechanical work rate (MWR) using the DPMOD and DPOLD. During the last minute of each test, the mean oxygen uptake (VO2) and respiratory exchange ratio (RER) were analyzed, from which the metabolic rate (MR) and gross efficiency (GE) were calculated. In addition, the difference between pretest and posttest blood-lactate concentrations (BLadiff) was determined. For each technique, skiers’ joint angles (i.e., heel, ankle, knee, hip, shoulder, and elbow) were analyzed at the highest and lowest positions during the double-poling cycle. Paired-samples t-tests were used to investigate differences between DPMOD and DPOLD outcomes. There were no significant differences in either VO2mean, MR, GE, or BLadiff (all P > 0.05) between the DPMOD and DPOLD tests. DPMOD execution was associated with a higher RER (P < 0.05). Significant technique-specific differences were found in either the highest and/or the lowest position for all six analyzed joint angles (all P < 0.001). Hence, despite decades of double-poling technique development, which is reflected in the significant biomechanical differences between DPOLD and DPMOD execution, at submaximal work intensity, the modern technique is not more energy efficient than the old-fashioned technique. 

Purpose: To examine the relationship between cardiorespiratory and accelerometer-derived measures of exercise during trail running and determine the influence of accelerometer location. Methods: Eight trail runners (7 males and 1 female; age 26 [5] y; maximal oxygen consumption [˙VO2] 70 [6] mL·kg−1·min−1) completed a 7-km trail run (elevation gain: 486 m), with concurrent measurements of ˙VO2, heart rate, and accelerations recorded from 3 triaxial accelerometers attached at the upper spine, lower spine, and pelvis. External exercise intensity was quantified from the accelerometers using PlayerLoad™ per minute and accelerometry-derived average net force. External exercise volume was calculated using accumulated PlayerLoad and the product of average net force and duration (impulse). Internal intensity was calculated using heart rate and ˙VO2-metrics; internal volume was calculated from total energy expenditure (work). All metrics were analyzed during both uphill (UH) and downhill (DH) sections of the trail run. Results:PlayerLoad and average net force were greater during DH compared with UH for all sensor locations (P ≤ .004). For all accelerometer metrics, there was a sensor position × gradient interaction (F2,1429.003; P <.001). The upper spine was lower compared with both pelvis (P ≤ .003) and lower spine (P ≤ .002) for all accelerometer metrics during both UH and DH running. Relationships between accelerometer and cardiorespiratory measures during UH running ranged from moderate negative to moderate positive (r = −.31 to .41). Relationships were stronger during DH running where there was a nearly perfect correlation between work and impulse (r = .91; P < .001). Conclusions: Simultaneous monitoring of cardiorespiratory and accelerometer-derived measures during trail running is suggested because of the disparity between internal and external intensities during changes in gradient. Sensor positioning close to the center of mass is recommended.

The rise of wearable sensors to measure lactate content in human sweat during sports activities has attracted the attention of physiologists given the potential of these "analytical tools" to provide real-time information. Beyond the assessment of the sensing technology per se, which, in fact, has not rigorously been validated yet in controlled conditions, there are many open questions about the true usefulness of such wearable sensors in real scenarios. On the one hand, the evidence for the origin of sweat lactate (e.g., via the sweat gland, derivation from blood, or other alternative mechanisms), its high concentration (1-25 mM or even higher) compared to levels in the blood, and the possible correlation between different biofluids (particularly blood) is rather contradictory and generates vivid debate in the field. On the other hand, it is important to point out that accurate detection of sweat lactate is highly dependent on the procedure used to collect and/or reach the fluid, and this can likely explain the large discrepancies reported in the literature. In brief, this paper provides our vision of the current state of the field and a thoughtful evaluation of the possible reasons for present controversies, together with an analysis of the impact of wearable sweat lactate sensors in the physiological context. Finally, although there is not yet overwhelming scientific evidence to provide an unequivocal answer to whether wearable sweat lactate sensors can contribute to sports physiology, we still understand the importance to bring this challenging question up-front to create awareness and guidance in the development, validation, and implementation of wearable sensors.

Background: The relationship between head impact dose andobservable functional deficits remains unclear. While studieshave almost exclusively examined American football athletes,in Olympic athletes there are almost no data that explore thisrelationship.

Objective: We aimed to use an impact monitoring mouthguard(IMM) to quantify head impact doses in Olympic and non-Olympic Sports, identifying high-energy impacts on video as‘No-go’ per the NFL protocol.

Design: Retrospective meta-analysis from American football,basketball, boxing, ice hockey, karate, lacrosse, mixed martialarts, rugby, tae-kwon-do, soccer.

Setting: Sporting field.

Patients (or Participants): 4500 impacts over 800 player-games.

Interventions (or Assessment of Risk Factors): Impact doseswhere the athlete was observed as ‘no-go’.

Main Outcome Measurements: Kinetic energy transfer (KE),risk-weighted exposure (RWE), peak scalar linear acceleration(PLA), peak scalar linear velocity (PLV), peak scalar angularacceleration (PAA), peak scalar angular velocity (PAV), impactlocation, impact direction, ‘No-go’ status.

Results: The median KE, RWE, PLA, PAA, PLV and PAV was 5J, 0.0002, 20 g, 1500 rad/s2, 10 rad/s and 1.5 m/s, respectively.American football athletes sustained the highest energyimpact doses, boxers and mixed-martial artists sustained thehighest cumulative dose for a day of competition. Ice hockeyhad the highest rate of ‘no-go’ impacts versus total impactscollected. Karate had the highest rotational kinematics. Of thenine (9) highest energy impacts to the side and rear of thehead, all were ‘no-go’ impacts. Of the top eight (8) highestenergy impacts to the front of the head, none were ‘no-go’impacts.

Conclusions: ‘No-go’ observations occurred in high energyimpact doses to the rear and the sides of the head, while similarimpact doses to the forehead seemed tolerable. ProspectiveOlympic athlete impact monitoring could help identify riskyexposures.

The International Ski Federation (FIS) implemented new ski regulation prior to the 2012/2013 season for men and women and for the men again prior to the 2017/2018 season in an effort to increase skiers’ safety in the Giant Slalom (GS) event in the Alpine World Cup (WC). At present, no study has investigated how these changes impacted total race times, gate-to-gate times or number of gates per race. Hence, the purpose of this study was to investigate how the regulation changes have affected these parameters. Data were collected from the official result lists, by the FIS, for the GS event during 15 WC seasons (2005/2006-2019/2020), for men and women, respectively and grouped into Rule 1 (2005/2006-2011/2012), Rule 2 (2012/2013-2016/2017) and Rule 3 (2017/2018-2019/2020). Differences (for total race time, gate-to-gate times and number of gates) between rules were analyzed using Mann-Whitney tests and Kruskal-Wallis rank sum tests for women and men, respectively. For male skiers, the race time during Rule 2 was 152.51 (138.72-157.55) s, which was significantly slower (p < 0.01) than Rule 1, 147.42 (143.13-154.26) s and to Rule 3, 149.37 (135.63-158.32) s (p<0.05). For women, race times during Rule 1 was significant slower (p<0.001, r=0.23, df =455, U=939852.5, z = 12.079) than Rule 2, 141.3 (132.71-148.78) s vs. 137.12 (125.05-146.78) s. The men’s gate-to-gate times increased for Rule 2 compared to Rule 3, 1.49 (1.45-1.55) s vs. 1.48 (1.45-1.52) s, p<0.05), whereas the women’s gate-to-gate times decreased for Rule 2 compared to Rule 1, 1.53 (1.48-1.57) s, vs 1.57 (1.52-1.62) s, p<0.001. Changing the ski equipment regulations affected men and women differently as well the course setting and should not be considered as the sole effort to reduce skiing speed and risk of injury in GS in the alpine WC.

INTRODUCTION: Pacing strategies in cross-country skiing (XCS) are largely influenced by the course topography [1]. Recent research has identified that skiing velocity during some key track sections (i.e. the micro-pacing strategy) was related to faster race times [2]. Specifically, skiing velocity during transitions between uphill, flat and downhill sections were strongly related to faster classic XCS sprint race times among female skiers [2]. Previous research has also shown that pacing strategies might vary between techniques (i.e. classic vs. skate) [1] and sexes [3]. Therefore, this study aimed to examine the relationship between micro-pacing strategies and performance during a freestyle XCS distance race in women and men.

METHODS: Nine female and 10 male XCS athletes wore a GNSS device (Catapult OptimEye S5; 10 Hz) during a senior FIS-sanctioned freestyle distance race. The race lap was 4892 m in distance with 165 m of vertical climbing. The women completed two laps (9964 m), while the men completed three laps (14678 m). The course was divided into uphill (S1, S3, S5, S7), downhill (S2, S4, S6, S8) and flat sections (S9) for analyses. In order to compare skiers’ velocities at the same track locations, GNSS positioning data were resampled at every 1-m interval along the course. Statistical parametric mapping (SPM; linear regression) was used to determine the track positions where instantaneous skiing velocity was significantly associated with race time.

RESULTS: Race time was associated with velocity during parts of S1 (the second longest climb) on lap 2 for both sexes (t ≥ 4.206, p < 0.001) and on lap 3 for men (t = 4.308, p = 0.047). By contrast, race time was unrelated to velocity during S3 (the shortest climb) for both sexes. Race time was related to velocity during parts of S5 (the longest climb) on lap 1 for women (t = 4.663, p < 0.001) and on laps 2 and 3 for men (t ≥ 4.031, p ≤ 0.009). While race time was not related to velocity during S7 (the second shortest climb) for men, it was for women on lap 1 (t = 3.871, p = 0.002). Race time was largely unrelated to velocity during all downhill sections for both sexes. Finally, race time was related to velocity through S9 (the flat section) for women (t = 3.716, p = 0.001), but not for men.

CONCLUSION: SPM analyses revealed specific uphill and flat track sections where athletes with faster race times skied with higher velocities, compared to athletes with slower race times. Specifically, more successful women adopted more aggressive micro-pacing strategies on some parts of the three longer uphill sections (S1, S5, S7), as well as on the flat section of the course (S9). The more successful men also adopted more aggressive micro-pacing strategies on some parts of the two longest uphill sections (S1, S5). Coaches and athletes can use this information to optimise micro-pacing strategies and improve performance.

1. Stöggl et al. (2018); 2. Ihalainen et al. (2020); 3. Andersson et al. (2019)

The purpose of this study was to develop a method which uses positioning data to analyse player-specific skating characteristics and to investigate the possibility to use machine learning to generate new individual and game-specific training drills. A real-time local positioning system was used to collect positioning data from a professional ice hockey team in the Swedish Hockey League. Positioning data and video were synchronized, and nine different skating characteristics were manually identified and tagged for two forwards. A cost function was developed to generate individual, continuous skating sequences and to create new individual and game-specific skating drills. Skating forward was the most commonly used skating characteristic for both player but the numbers of times the players used the different skating characteristics varied, (H(8)=23.2,  p=0.003). The number of skating characteristics between the two players varied, (χ2 (8, N=688) =3 4.0, p<0.001) as well as the time spent within each skating characteristic (p<0.001). The presented method can be used for performance analysis and shows promising results for creating individual and game-specific tests and training drills for ice hockey players, based on individual and game-specific skating characteristics

Our aims were to measure anthropometric and oxygen uptake (V&#x2D9;" role="presentation" style="box-sizing: border-box; display: inline; line-height: normal; font-size: 20px; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; color: rgb(62, 61, 64); font-family: Georgia, "Times New Roman", Times, serif; position: relative; outline: 0px !important;">V˙V˙O2) variables in the laboratory, to measure kinetic and stride characteristics during a trail running time trial, and then analyse the data for correlations with trail running performance. Runners (13 men, 4 women: mean age: 29 ± 5 years; stature: 179.5 ± 0.8 cm; body mass: 69.1 ± 7.4 kg) performed laboratory tests to determine V&#x2D9;" role="presentation" style="box-sizing: border-box; display: inline; line-height: normal; font-size: 20px; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; color: rgb(62, 61, 64); font-family: Georgia, "Times New Roman", Times, serif; position: relative; outline: 0px !important;">V˙V˙O2 max, running economy (RE), and anthropometric characteristics. On a separate day they performed an outdoor trail running time trial (two 3.5 km laps, total climb: 486 m) while we collected kinetic and time data. Comparing lap 2 with lap 1 (19:40 ± 1:57 min vs. 21:08 ± 2:09 min, P < 0.001), runners lost most time on the uphill sections and least on technical downhills (-2.5 ± 9.1 s). Inter-individual performance varied most for the downhills (CV > 25%) and least on flat terrain (CV < 10%). Overall stride cycle and ground contact time (GCT) were shorter in downhill than uphill sections (0.64 ± 0.03 vs. 0.84 ± 0.09 s; 0.26 ± 0.03 vs. 0.46 ± 0.90 s, both P < 0.001). Force impulse was greatest on uphill (248 ± 46 vs. 175 ± 24 Ns, P < 0.001) and related to GCT (r = 0.904, P< 0.001). Peak force was greater during downhill than during uphill running (1106 ± 135 vs. 959 ± 104 N, P< 0.01). Performance was related to absolute and relative V&#x2D9;" role="presentation" style="box-sizing: border-box; display: inline; line-height: normal; font-size: 20px; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; color: rgb(62, 61, 64); font-family: Georgia, "Times New Roman", Times, serif; position: relative; outline: 0px !important;">V˙V˙O2 max (P < 0.01), vertical uphill treadmill speed (P < 0.001) and fat percent (P < 0.01). Running uphill involved the greatest impulse per step due to longer GCT while downhill running generated the highest peak forces. V&#x2D9;" role="presentation" style="box-sizing: border-box; display: inline; line-height: normal; font-size: 20px; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; color: rgb(62, 61, 64); font-family: Georgia, "Times New Roman", Times, serif; position: relative; outline: 0px !important;">V˙V˙O2 max, vertical running speed and fat percent are important predictors for trail running performance. Performance between runners varied the most on downhills throughout the course, while pacing resembled a reversed J pattern. Future studies should focus on longer competition distances to verify these findings and with application of measures of 3D kinematics.

Pacing strategies in cross-country skiing have been investigated in several studies. However, none of the previous studies have been verified by collected skiing data giving the skiing velocities along a measured track. These can be used to calculate the propulsive power output. Collected real-time positioning data from a cross-country sprint skiing race were used to estimate the propulsive power by applying a power balance model. Analyses were made for the time-trial and the final for one female and one male skier. The average propulsive power over the whole race times were 311 and 296 W during the time trial and 400 and 386 W during the final, for the female and male skier, respectively. Compared to the average propulsive power over the whole race, the average active propulsive phases were calculated as 33 and 44% higher in the time trials and 36 and 37% higher in the finals for the female and male, respectively. The current study presents a novel approach to use real-time positioning data to estimate continuous propulsive power during cross-country sprint skiing, enabling in-depth analyses of power output and pacing strategies.

INTRODUCTION: Research investigating the correlation between impairment and key performance indicators in para-alpine skiing is needed for a future evidence based classification system (Tweedy and Vanlandewijck 2011). Only a little research in para-alpine skiing exists, especially in the standing classes LW5/7 and LW6/8 (impairment of one or two arms). The use of arms and poles affects performance in alpine skiing[OM1]  but how underlying biomechanical parameters as kinematics and kinetics are related to performance has to the authors knowledge not been studied before.

PURPOSE: The purpose of this study was to further the understanding of slalom skiing with two ski poles, one pole or without poles (c2, c1, c0) by investigating the biomechanical differences (kinematics and foot plantar pressure) for able-bodied athletes.

METHODS: Ten able-bodied right-handed junior skiers on national level were tested in three conditions - c0, c1, c2, while skiing a slalom course (28 gates, 62 m vertical drop). 3D kinematic data were collected at 200 Hz by 12 inertial motion units (Myomotion, Noraxon Inc, USA) placed on head, trunk, pelvis, arms and legs. Ski-time was measured with timing gates (XS Crystal Synchronization, Brower Timing Systems, USA) and kinetics were measured with pressure insoles (Pedar, Novel GmbH, Germany) placed inside each ski boot. Normal ground reaction force (nGRF) and relative force time integrals (relFTI) were calculated according to Melai et. Al (2011). Kinematics and plantar pressure were analysed over three right and left turns and averaged for each condition. Right turn and left turn were distinguished at the time point where the shank was standing vertical.

RESULTS: Time analysis showed that time increased with the use of less ski poles, mean difference between c1c2 of 1.27 ± 1.69 s (p=0.001) and between c0c1 of 0.73 ± 1.95 s (p=0.003[OM2] ). Kinematic analysis showed that different approaches were used to attack a slalom gate in condition c1 and c0, for example slalom-attack, giant slalom attack or opposite arm attack. Interquartile range and median of the body angles [OM3] differed between conditions, e.g. lower median (indicate less deviation from anatomical  basic position[OM4] ) in c0 and mostly lower than in c1 and c2. Furthermore, relFTI was related to the turning side (right or left turn) and showed largest asymmetry for condition c1.

CONCLUSION: Reduced balance due to missing ski pole/s lead to compensatory movements in the upper body and asymmetry in foot plantar pressure. This reduced the ability for a controlled turn. Whether or not only reduced balance or also the skiers low experience of skiing with reduced number of poles influenced the performance remains unclear.

REFERENCES

Melai, Tom, T. Herman IJzerman, Nicolaas C. Schaper, Ton L.H. de Lange, Paul J.B. Willems, Kenneth Meijer, Aloysius G. Lieverse, and Hans H.C.M. Savelberg. 2011. ‘Calculation of Plantar Pressure Time Integral, an Alternative Approach’. Gait & Posture 34 (3): 379–83. https://doi.org/10.1016/j.gaitpost.2011.06.005.

Tweedy, S. M., and Y. C. Vanlandewijck. 2011. ‘International Paralympic Committee Position Stand--Background and Scientific Principles of Classification in Paralympic Sport’. British Journal of Sports Medicine 45 (4): 259–69. https://doi.org/10.1136/bjsm.2009.065060.

This study investigates the feasibility to use a passive marker motion capture system on ice to collect 3D kinematics of slap shots and one timers. Kinematic data were collected within a volume of 40x15x2 m by 20 motion capture cameras at 300 Hz, a resolution of 12 megapixels and a mean residual for all cameras of 3.4±2.5 mm, at a distance of 11.6 m. Puck velocity, blade velocity, ice contact time and distance to the puck were analysed for ten consecutive shots for each technique, for two professional ice hockey players. The total mean puck velocity was 38.0 ± 2.7 m/s vs. 36.4 ± 1.0 m/s. (p=0.053), for one timers and slap shots respectively. One player had higher puck velocity with one timers compared to slap shots 40.5 ± 1.0 m/s vs. 36.9 ± 1.0 m/s (p=0.001). Puck contact time was longer for slap shots than for one timers, 0.020 ± 0.002 s vs. 0.015 ± 0.002 s, (p<0.001). The motion capture system allowed continuous kinematic analyses of the puck and blade velocities, ice contact times and detailed stance information. The results demonstrate the possibilities to use motion capture systems to collect and analyse shooting kinematics on ice, in detail.

This study investigates the feasibility to use a passive marker motion capture system on ice to collect 3D kinematics of slap shots and one timers. Kinematic data were collected within a volume of 40×15×2 m by 20 motion capture cameras at 300 Hz, a resolution of 12 megapixels and a mean residual for all cameras of 3.4±2.5 mm, at a distance of 11.6 m. Puck velocity, blade velocity, ice contact time and distance to the puck were analysed for ten consecutive shots for each technique, for two professional ice hockey players. The total mean puck velocity was 38.0 ± 2.7 m/s vs. 36.4 ± 1.0 m/s. (p=0.053), for one timers and slap shots respectively. One player had higher puck velocity with one timers compared to slap shots 40.5 ± 1.0 m/s vs. 36.9 ± 1.0 m/s (p=0.001). Puck contact time was longer for slap shots than for one timers, 0.020 ± 0.002 s vs. 0.015 ± 0.002 s, (p<0.001). The motion capture system allowed continuous kinematic analyses of the puck and blade velocities, ice contact times and detailed stance information. The results demonstrate the possibilities to use motion capture systems to collect and analyse shooting kinematics on ice, in detail.

Ice hockey is a physical demanding sport with high intensity and repetitive start and stop movements. Hence, players need to have excellent physical condition and ice skating skills with good acceleration and sprint capacities. However, little biomechanical research has been conducted on elite ice hockey players to analyse applicable key performance indicators of skating acceleration and short sprint performance. The aim of the study was to collect plantar forces data of elite ice hockey players during short sprints in order to analyse and identify plausible performance indicators. With institutional ethics approval, twelve professional male ice hockey players, (Age 22.8 ± 5.2 years, height 185.6 ± 5.0 cm, weight 86.9 ± 6.2 kg) from the Swedish Hockey League participated in the study. Following an individual warm up, each player performed three maximal sprints (18.4 m) from a stationary position, with three minutes of rest between each sprint. Sprint time was collected with timing gates (Brower Timing system, USA). The best trial for each player was chosen for further analysis. Plantar forces were collected at 100 Hz with pressure insoles (Novel GmbH, Germany), placed in both skates (Buckeridge et al., 2015, PLOS ONE, 10, 5). Analyses were made for stride rate, symmetry left-right, contact time, force production and impulse. Only the step frequency, 3.35 ± 0.38 strides/s was correlated to skating performance (r = -0.6, P < 0.05). For the second to seventh step, the mean contact time was 0.26 ± 0.04 s, the mean force was 844 ± 152 N and the mean peak force was 1335 ± 224 N. The mean impulse was 230 ± 52 Ns and the group showed greater force production for the left leg compared to the right leg −2.07 ± 9.08 %. The present study is the first study to analyse plantar forces on professional ice hockey players. The significance of stride rate is in line with previous research (Renaud et al., 2017, Sports Engineering, 20, 255–266) whereas the plantar force production is higher, compared to findings by Buckeridge et al. (2015). This is likely explained by the use of higher skilled players in the present study. Still, plantar force production is not significant for performance which points to the importance of skating kinematics and/or shear forces. Hence, the combination of kinetics and 3D kinematics on ice is important to enhance the knowledge about skating performance of elite ice hockey players as well as developing a kinetic measurement system to measure shear forces in combination with plantar forces.

Purpose:

To 1) investigate the cardiorespiratory and metabolic response of trail running and 2) evaluate whether heart rate (HR) adequately reflects the exercise intensity or whether the tissue saturation index (TSI) could provide a more accurate measure when running in hilly terrain.

Methods:

Seventeen competitive runners (female: n=4, V’O_2max: 55±6 mL·kg⁻¹·min⁻¹; male: n=13, V’O_2max: 68±6 mL·kg⁻¹·min⁻¹) performed a time trial on an off-road trail course. The course was made up of two laps covering a total distance of 7 km and included six steep up- and downhill sections with an elevation gain of 486 m. All runners were equipped with a portable breath-by-breath gas analyzer, HR belt, global positioning system receiver and near-infrared spectroscopy (NIRS) device to measure the TSI.

Results:

During the trail run, the exercise intensity within the uphill and downhill sections was 94±2% and 91±3% of HR_max, 84±8% and 68±7% of V’O_2max, respectively. The oxygen uptake (V’O₂) increased within the uphill and decreased within the downhill sections (P< .01). While HR was unaffected by the altering slope conditions, the TSI was inversely correlated to the changes in V’O₂ (r = - .70, P< .05).

Conclusions:

The HR was unaffected by the continuously changing exercise intensity, however, the TSI reflected the alternations in V’O₂. Recently used exclusively for scientific purpose, this NIRS based variable may offer a more accurate alternative to HR to monitor running intensity in the future, especially for training and competition in hilly terrain.

Introduction Elite alpine skiers frequently adjust insoles, boots and skis to optimize skiing performance. There are numerous different constructions of custom made insoles. However, nobody has, to the authors’ knowledge, investigated the mechanisms behind a plausible performance increase. The purpose of the study was therefore to investigate the potential difference in pressure distribution under the feet when skiing with regular insoles compared to custom made insoles. Method A pre-study investigated differently constructed insoles and their possible effects on the pressure distribution under the feet. One test subject performed different squat and fly-wheel exercises with six differently constructed insoles. Kinetics and 3D-kinematics were collected to identify possible differences. One insole construction, with a flat bottom and a semi-soft upper layer, was thereafter chosen to be used for field tests. Nine professional skiers, including both race skiers and full time ski instructors, were recruited for the field tests. Each skier performed in a randomized order, three runs with a standard insole and three runs with a custom made insole. Plantar pressure under the feet was measured with the Pedar Mobile System at 100 Hz, for eight consecutive carving turns. The skiers were instructed to have the smallest possible time difference between all runs. The three runs for each situation were synchronized and the mean total, forefoot and midfoot pressure distributions were calculated. Results The pre-study results show that the pressure distribution between foot and insole and between insole and ski-boot depends on the insole construction. The mean time for all 54 runs was 26.62 ± 2.41 s and the mean individual time difference between the fastest and the slowest runs was 0.62 ± 0.33 s. All skiers showed large individual differences in percentage of “used” area under the feet, between the two types of insoles (5-80%). When skiing with the custom made insole, the total mean difference in percentage usage of the forefoot was -17 ± 19% and 8 ± 12% for the midfoot. Discussion The results show that the pressure distribution under the feet depends on the type of insole. However, the effect of a custom made insole is very individual. Hence, when performing studies of skiing kinetics and/or equipment, it is of vast importance that all subjects use similarly constructed custom made insoles. It can also be hypothesized that e.g., different canting angles of the ski-boot, affect the skier differently depending on the type of insole. Our suggestion is therefore to perform measurements to optimize the insoles before investigating and optimizing canting angles. The results also show that custom made insoles can assist the skier to utilize different areas of the foot. However, future studies are needed to investigate whether the decreased usage of the forefoot affects the overall aggressiveness of the setup and whether custom made insoles have a positive effect on skiing performance.

Sports engineering can be considered as the bridge between the knowledge of sports science and the principles of engineering and has an important role not only in improving the athletic performance, but also in increasing the safety of the athletes. Testing and optimization of sports equipment and athletic performance are essential for supporting athletes in their quest to reach the podium. However, most of the equipment used by world-class athletes is chosen based only on subjective tests and the athletes’ feelings. Consequently, one of the aims of this thesis was to combine mechanics and mathematics to develop new objective test methods for sports equipment. Another objective was to investigate the possibility to accurately track and analyse cross-country skiing performance by using a real-time locating system. A long term aim is the contribution to increased knowledge about objective test and analysis methods in sports. The main methodological advancements are the modification of established test methods for sports equipment and the implementation of spline-interpolated measured positioning data to evaluate cross-country skiing performance. The first two papers show that it is possible to design objective yet sport specific test methods for different sports equipment. New test devices and methodologies are proposed for alpine ski helmets and cross-country ski poles. The third paper gives suggestions for improved test setups and theoretical simulations are introduced for glide tests of skis. It is shown, it the fourth paper, that data from a real-time locating system in combination with a spline model offers considerable potential for performance analysis in cross-country sprint skiing. In the last paper, for the first time, propulsive power during a cross-country sprint skiing race is estimated by applying a power balance model to spline-interpolated measured positioning data, enabling in-depth analyses of power output and pacing strategies in cross-country skiing. Even though it has not been a first priority aim in this work, the results from the first two papers have been used by manufacturers to design new helmets with increased safety properties and cross-country ski poles with increased force transfer properties. In summary, the results of this thesis demonstrate the feasibility of using mechanics and mathematics to increase the objectiveness and relevance when analysing sports equipment and athletic performance.

For the first time, we investigate here the possibility of using a real-time locating system (RTLS) to track cross-country skiers during a competition. For validation, three RTLS tags were attached to the antenna of a real-time kinematics global navigation satellite system (RTK GNSS) carried by a skier, skiing the course at three different intensities. In addition, RTLS data were collected from 70 racers during a FIS cross-country skiing sprint race. Spline interpolations were fitted to the RTLS data. In comparison to the RTK GNSS, the spline models for the three RTLS tags overestimated the mean skiing velocity by 5% and 2% at low and medium intensities, respectively, with no difference between the two systems during high intensity. The corresponding overestimations of the peak velocity at skiing intensities were 15%, 10% and 8%, respectively. A decimated sampling frequency for the RTLS data from 50 Hz to 0.5 Hz resulted in lower typical mean errors for the x- (0.53 m vs. 1.40 m), y- (0.31 m vs. 1.36 m) and z-axis (0.10 m vs. 0.20 m). The spline models based on 0.5 Hz and 1 Hz RTLS data overestimated the finishing times by on average of 0.5 s and 0.3 s, respectively. If a sufficient number of locators is utilized and the number of tags simultaneously recorded is limited, this RTLS can track cross-country skiers accurately. In conclusion, a low RTLS sampling frequency in combination with a spline model offer considerable potential for analyzing performance during cross-country sprint skiing.

ntroduction The most frequently used analysis method in alpine skiing is video footage. However, using video footage to identifying key performance indicators (KPIs) and other characteristics are difficult as each coach analyzes video footage in a subjective manner, which decreases the reliability of the analyses. Even though alpine skiing is a “closed sport”, without any external disturbing moments, each race is unique therefore never identical. It is thus difficult for coaches to know the validity and reliability of their analyses as the majority of the video footage of alpine skiers is captured during training, not racing. A large number of analyzed races with high reliability could therefore facilitate to identify KPIs in alpine skiing. The purpose of this study was to use the standardized typical error to explore the possibility to use telecasting to analyze performance and skiing characteristics in world cup slalom races. Method Standard telecasting footage (25 fps) from four different WC-races (eight runs) was used for analyzing turn times for eleven skiers (nine males and two females). The footage was analyzed at three separate situations, by two different alpine World Cup coaches and one video analyst. Turn time was defined as boot passage of the gate and all video analyses were made in DartFish ProSuite 6. Typical error (TE) was calculated by; TE=σ_diff/√(N_obs ) The standardized typical error (STE) was calculated by; TE= TE/√(((n_1-1)^2 σ_1^2+(n_2-1)^2 σ_2^2 ) /((n_1+n_2-2))-TE^2 ) The index described by Hopkins [1] was used for evaluating the influence of the STE. Results The mean turn time for the male skiers was 0.83 ± 0.18 s, with a coefficient of variation of 22%. The mean turn time for the two female skiers was 0.85 ± 0.19 s and the coefficient of variation was 22%. The TE between the different analyses was 0.03 s and the STE was 0.14. The results provide a detailed analysis of gate-to-gate times for each skier. Discussion The TE value of 0.03 s is most likely due to the 25 fps telecasting footage, where each frame is 0.04 s. The analysts must therefore choose one frame if the point of interest is between two frames. Hence, TE will presumably decrease with increase framerate. As the STE < 0.2, the disagreement between the different analysts can be considered as trivial [1, 2]. We here show how the STE can be used to identify inter-analyst reliability of alpine skiing video analyses. Furthermore, the presented method provides a robust, cheap and effective method to objectively analyze skiing performance and identifying plausible key performance indicators in alpine skiing. References 1. Hopkins, W., Reliability from consecutive pairs of trials (Excel spreadsheet). A new view of statistics, 2000. 2. Liu, H., et al., Inter-operator reliability of live football match statistics from OPTA Sportsdata. International Journal of Performance Analysis in Sport, 2013. 13(3): p. 803-821.

Alpine skiing can be considered as a “closed sport” where each athlete is alone in the course without any external disturbing moments. However, each alpine race is unique therefore never identical. In addition, the condition of the course is constantly changing as each skier makes new tracks in the snow. Identifying key performance indicators (KPI) and other characteristics are therefore difficult. The most frequently used analysis method in alpine skiing is video footage. However, it is not always possible for coaches to cover a complete course as they can be several kilometers long as e.g. downhill skiing. The purpose of this study was thus to explore the possibility to use telecasting to analyze performance and skiing characteristics in world cup slalom races to identify possible KPI.

Product testing and development are essential parts in sports and for the athletes in their quest to reach the podium. Manufacturers of sports equipment often use basic test methods which do not test the equipment in a sports specific way. Much of the equipment used by world-class athletes is chosen based only on subjective tests and the athletes’ feelings. One short term aim was therefore to develop test methods for objective tests of sports equipment that also tested the equipment in a sports  specific  way.  Another  aim  was  to  integrate  mechanics  and  simulations  to  enhance  the understanding of the test results. The more long term aims are to contribute to increased theoretical knowledge regarding test methods for sports equipment and to contribute to the development of test  methods  to  create  new  and  better  sports  equipment.  Experimental  tests  combined  with simulations  can  give  valuable  information  to  improve  the  performance  and  safety  of  sports equipment. Three studies dealt with the issue of objective yet sport specific test methods for sports equipment. The main methodological advancement is the modification of established test methods together  with  conventional  mechanics  calculations.  New  test  devices  and  methodologies  are proposed for alpine ski helmets and cross-country ski poles. Suggestions are given for improved test setups as well as theoretical simulation are introduced for glide tests of skis. The results show how sport   specific   test   methodologies   together   with   theoretical   calculations   can   improve   the objectiveness and relevance when testing sports equipment. However, the collected and used data require high precision to obtain high accuracy in the simulations. High data accuracy can be an issue in field measurements but also due to manufacturers not disclosing key material data. Still, the used methods  and  calculations  in  this  thesis  produce  relevant  and  reliable  results  which  can  be implemented to accurate evaluations of different sports equipment. Even though it has not been a first priority aim in this work, the results from the alpine helmet study have been used by helmet manufacturers to design new helmets with increased safety properties. This further show how an objective and sport specific test approach together with theoretical simulation can improve sports equipment and in the longer perspective, also the athletes’ performances.

Although today's ski waxing chemicals and micro-machining techniques of the ski base are highly sophisticated, objective procedures for testing and verification of the results have not yet been developed and evaluation is based on comparison of subjective experience. The purpose of the present study was thus to compare different setups for testing the glide of cross-country skis. Two differently waxed ski pairs were tested for glide inside a ski tunnel. Inertial measurement units (IMUs) were attached to each ski; instantaneous velocities monitored by three different speed-traps; the velocities during the acceleration phase determined by Doppler radar. Kinetic, potential and total energy, giving the energy dissipation, were calculated for four representative trials during the acceleration phase. No reliable data were obtained from the IMUs due to high drift. The mean maximal velocity for the two ski pairs were 6.97, s = 0.09 and 6.70, s = 0.09 m·s − 1, respectively. Higher differences between the skis were identified during the retardation phase compared to the acceleration phase. The mean difference between the velocities determined by the speed-trap and Doppler radar was 0.6, s = 1%, demonstrating that the latter provides accurate data for evaluation of gliding characteristics and performance. However, theoretical confirmation of the friction coefficient, on the basis of data provided by Doppler radar and energy calculations requires exact measurements of the inclination and topography of the track in question.

Background: Astronauts are required to perform both resistance and aerobic exercise while in orbit. This study assessed the aerobic energy yield and related physiological measurements using a nongravity dependent flywheel device designed for both resistance and aerobic exercise (RAD) in space. Methods: Eight physically active men and women performed all-out rowing on the RAD. For comparison, exercise was also carried out employing a commercially available rowing ergometer (C2). Results: Peak oxygen uptake during exercise using RAD and C2 averaged 3.11 ± 0.49 and 3.18 ± 0.50 L · min-1 respectively. Similarly, peak plasma lactate concentration (9.6 vs. 11.2 mmol · L-1), heart rate (183 vs. 184 bpm), and rate of perceived exertion (15.8 vs. 16.0) were comparable across exercise using the two devices. Discussion: Collectively, the results suggest that this novel exercise modality offers cardiovascular and metabolic responses, and thus aerobic exercise stimulus that is equally effective as that evoked by established technology for indoor rowing. Given the need for physiologically sound and highly effective exercise countermeasures that features small mass and envelope, and allows for resistance and aerobic exercise in a single apparatus, we believe this novel hardware should be considered for use in space. © by the Aerospace Medical Association, Alexandria, VA.

This study aimed to profile the activity patterns of elite downhill (DH) mountain bikers during off-road descending, and to determine the influence of course types on activity patterns. Six male elite DH mountain bikers (age 20 ± 2 yrs; stature 178.8 ± 3.1 cm; body mass 75.0 ± 3.0 kg) performed single runs on one man-made (MM) and one natural terrain (NT) DH courses under race conditions. A 5 Hz global positioning systems (GPS) unit, including a 100 Hz triaxial accelerometer, was positioned in a neoprene harness between the C7 and T2 vertebrae on each rider. GPS was used to determine the temporal characteristics of each run for velocity, run time, distance, effort, heart rate (HR), rider load (RLd) which reflects instantaneous rate of change in acceleration, and accumulated rider load (RLdAcc), which reflects change in acceleration over the event duration. Significant differences were found between NT and MM courses for mean velocity (p<.001), peak velocity (p=.014), mean RLd (p=.001) and peak RLd (p=.002). Significant differences were also found both within and between courses for all velocity parameters, when analysed by intensity zone (p<.05). No significant differences were found between courses for HR parameters by zone, though significant differences were revealed between HR zones within courses (p<.05). This study indicates that course terrain has a significant impact on the activity profiles of DH and that GPS can provide a practical means of monitoring these differences in activity.

Background:This study examined the effects of different levels of compression (0, 20 and 40 mmHg) produced byleg garments on selected psycho-physiological measures of performance while exposed to passive vibration (60 Hz,amplitude 4-6 mm) and performing 3-min of alpine skiing tuck position.Methods:Prior to, during and following the experiment the electromygraphic (EMG) activity of different muscles,cardio-respiratory data, changes in total hemoglobin, tissue oxygenation and oscillatory movement ofm. vastuslateralis, blood lactate and perceptual data of 12 highly trained alpine skiers were recorded. Maximal isometric kneeextension and flexion strength, balance, and jumping performance were assessed before and after the experiment.Results:Thekneeangle(−10°) and oscillatory movement (−20-25.5%) were lower with compression (P<0.05inall cases). The EMG activities of thetibialis anterior(20.2-28.9%),gastrocnemius medialis(4.9-15.1%),rectus femoris(9.6-23.5%), andvastus medialis(13.1-13.7%) muscles were all elevated by compression (P< 0.05 in all cases).Total hemoglobin was maintained during the 3-min period of simulated skiing with 20 or 40 mmHg compression,but the tissue saturation index was lower (P< 0.05) than with no compression. No differences in respiratory parameters,heart rate or blood lactate concentration were observed with or maximal isometric knee extension and flexionstrength, balance, and jumping performance following simulated skiing for 3 min in the downhill tuck positionwere the same as in the absence of compression.Conclusions:These findings demonstrate thatwith leg compression, alpine skiers could maintain a deeper tuckposition with less perceived exertion and greater deoxygenation of thevastus lateralismuscle, with nodifferences in whole-body oxygen consumption or blood lactate concentration. These changes occurred withoutcompromising maximal leg strength, jumping performance or balance. Accordingly, our results indicate that theuse of lower leg compression in the range of 20-40 mmHg may improve alpine skiing performance by allowing adeeper tuck position and lowering perceived exertion.

Alpine ski race helmets are subjected to multiple impacts during a race caused by the skiers hitting the gates on their way down the course. This study investigated the difference between expanded polystyrene (EPS) and expanded polypropylene (EPP) cores in alpine ski race helmets when subjected to repetitive violence, caused by alpine slalom gates. A special test rig was developed where a rotating slalom pole impacted the helmets with a velocity of 13.3 m·s^− 1. All helmets (six EPS and six EPP) were attached to a headform, monitored with a triaxial accelerometer at the center of mass. Each helmet sustained 1000 impacts and acceleration data were collected around every 200 impacts. No significant differences were observed between the first hit and after 1000 hits for either the EPS or the EPP helmets. However, the total group mean acceleration and mean peak acceleration were 15% and 16% higher, respectively, for the EPS series compared with the EPP series. Also, all EPS helmets showed cracked cores after 1000 impacts compared with 1 cracked EPP core. Findings suggest that EPP cores might be more suitable for absorbing multiple low impacts caused by alpine gates and that repeated violence is a relevant parameter to consider when constructing alpine ski race helmets.

The aim of the study was to develop an objective classification method for cross-country ski poles. A test device was designed to expose different pole models to maximal loading and impact tests. A load cell measured the axial forces in the pole shafts, and a laser distance meter measured shaft deflection when a load was applied via the wrist strap. In the loading tests, each shaft reached a plateau where no more force could be transferred. This maximal force transfer (MFT) value was a characteristic measure for flexural rigidity and thereby also strength. The developed test method enables a loading that is more similar to real-life skiing than a standard three-point bending test. Results show that the introduction of shaft indices for buckling strength is beneficial for comparison purposes. The MFT is a relevant parameter used in the characterization of poles. © 2013 International Sports Engineering Association.

Introduction

Mountain biking (MTB) is composed of several sub-disciplines, with Olympic Cross-Country (XCO) and Downhill (DH) being the most popular. Much of the current research on MTB pertains to the aerobic demands of XCO racing, with comparisons often made to road cycling. No studies have compared elite level XCO and DH bikers. Therefore, the aim of this study was to investigate the anaerobic power and cadence characteristics of elite XCO to DH riders.

Methods

Twelve male elite mountain bikers (n=6 XCO, n=6 DH; age 21.83 ± 3.71 yrs; stature 179.67 ± 4.40 cm; mass 72.50 ± 5.45 kg) took part in this study. An inertial load cycling test was performed as described in previous studies⁽³⁾,on an SRM cycle ergometer instrumented with a scientific version SRM Powermeter. Inertial load was adjusted to ensure riders achieved 130-150 revs.min^-1 within 4-7 s. Peak power (W_peak), cadence at W_peak (CAD_opt) and power to weight ratio (W.kg^-1) were calculated for each rider as the mean from 3 trials. Statistical differences between XCO and DH were determined using independent t-tests with significance set at p≤0.05.

Results

A significant difference between DH and XCO was found for CAD_opt (114.93 ± 5.41 and 107.96 ± 4.63 revs.min^-1, p<0.05), respectively. No other differences were revealed between groups. The mean recorded values for DH and XCO were 1137.76 ± 135.84 and 1113.86 ± 75.22 W for W_peak and 15.21 ± 2.05 and 15.95 ± 0.75 W.kg^-1 for power to weight ratio, respectively.

Discussion

The findings of comparable W_peak between groups may indicate that high anaerobic power is not a prerequisite for success in elite DH. However, significant differences were found in CAD_opt, where DH riders had a higher cadence when producing W_peak compared to XCO riders. This may reflect training specificity and the greater emphasis on repeated accelerations in DH⁽²⁾ and the lower cadences elicited by XCO riders⁽¹⁾. Further research is therefore warranted to compare laboratory and field-based performance in these two population groups.