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  • 1.
    Cedervall, Ylva
    et al.
    Institutionen för folkhälso- och vårdvetenskap, Geriatrik, Uppsala universitet.
    Halvorsen, Kjartan
    Department of Information Technology, Division of Systems and Control, Uppsala University.
    Åberg, Anna Cristina
    Department of Public Health and Caring Sciences/Geriatrics, Uppsala University.
    A longitudinal study of gait function and characteristics of gait disturbances in individuals with Alzheimer's disease2014In: Gait & Posture, ISSN 0966-6362, E-ISSN 1879-2219, Vol. 39, no 4, p. 1022-1027Article in journal (Refereed)
    Abstract [en]

    Walking in daily life places high demands on the interplay between cognitive and motor functions. A well-functioning dual-tasking ability is thus essential for walking safely. The aims were to study longitudinal changes in gait function during single- and dual-tasking over a period of two years among people with initially mild AD (n = 21). Data were collected on three occasions, twelve months apart. An optical motion capture system was used for three-dimensional gait analysis. Gait parameters were examined at comfortable gait speed during single-tasking, dual-tasking naming names, and naming animals. The dual-task cost for gait speed was pronounced at baseline (names 26%, animals 35%), and remained so during the study period. A significant (p < 0.05) longitudinal decline in gait speed and step length during single- and dual-tasking was observed, whereas double support time, step width and step height showed inconsistent results. Systematic visual examination of the motion capture files revealed that dual-tasking frequently resulted in gait disturbances. Three main characteristics of such disturbances were identified: Temporal disturbance, Spatial disturbance and Instability in single stance. These aberrant gait performances may affect gait stability and increase the risk of falling. Furthermore, the observed gait disturbances can contribute to understanding and explaining previous reported gait variability among individuals with AD. However, the role that dual-task testing and aberrant dual-task gait performance play in the identification of individuals with early signs of cognitive impairment and in predicting fall risk in AD remains to be studied.

  • 2.
    Elmgren Frykberg, Gunilla
    et al.
    Uppsala universitet, Rehabiliteringsmedicin.
    Thierfelder, Tomas
    Department of Energy and Technology, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Åberg, Anna Cristina
    Department of Public Health and Caring Sciences/Geriatrics, Uppsala University.
    Halvorsen, Kjartan
    Department of Information Technology, Division of Systems and Control, Uppsala University.
    Borg, Jörgen
    Department of Clinical Sciences, Rehabilitation Medicine, Karolinska Institutet, Danderyd University Hospital, Stockholm, Sweden.
    Hirschfeld, Helga
    Motor Control and Physical Therapy Research Laboratory, Division of Physiotherapy, Department of Neurobiology, Care Sciences and Society, Karolinska Institutet, Stockholm, Sweden.
    Impact of stroke on anterior–posterior force generation prior to seat-off during sit-to-walk2012In: Gait & Posture, ISSN 0966-6362, E-ISSN 1879-2219, Vol. 35, no 1, p. 56-60Article in journal (Refereed)
  • 3.
    Elmgren Frykberg, Gunilla
    et al.
    Department of Neuroscience, Rehabilitation Medicine, Uppsala University.
    Åberg, Anna Cristina
    Department of Public Health and Caring Sciences/Geriatrics, Uppsala University; Swedish School of Sport and Health Sciences, Stockholm, Sweden.
    Halvorsen, Kjartan
    Department of Information Technology, Division of Systems and Control, Uppsala University; School of Technology and Health, the Royal Institute of Technology, Stockholm, Sweden.
    Borg, Jörgen
    Department of Neuroscience/Rehabilitation Medicine, Uppsala University, Uppsala, Sweden.
    Hirschfeld, Helga
    Karolinska Institutet, Department of Neurobiology, Care Sciences and Society, Division of Physiotherapy.
    Temporal coordination of the sit-to-walk task in subjects with stroke and in controls2009In: Archives of Physical Medicine and Rehabilitation, ISSN 0003-9993, E-ISSN 1532-821X, Vol. 90, no 6, p. 1009-1017Article in journal (Refereed)
    Abstract [en]

    Objectives: To explore events and describe phases for temporal coordination of the sit-to-walk (STW) task, within a semistandardized set up, in subjects with stroke and matched controls. In addition, to assess variability of STW phase duration and to compare the relative duration of STW phases between the 2 groups.

    Design: Cross-sectional.

    Setting: Research laboratory.

    Participants: A convenience sample of persons with hemiparesis (n=10; age 50–67y), more than 6 months after stroke and 10 controls matched for sex, age, height, and body mass index.

    Interventions: Not applicable.

    Main Outcome Measures: Relative duration of STW phases, SE of measurement in percentage of the mean, and intraclass correlation coefficients (ICCs).

    Results: Four STW phases were defined: rise preparation, transition, primary gait initiation, and secondary gait initiation. The subjects with stroke needed 54% more time to complete the STW task than the controls did. ICCs ranged from .38 to .66 and .22 to .57 in the stroke and control groups, respectively. SEs of measurement in percentage of the mean values were high, particularly in the transition phase: 54.1% (stroke) and 50.4% (controls). The generalized linear model demonstrated that the relative duration of the transition phase was significantly longer in the stroke group.

    Conclusions: The present results extend existing knowledge by presenting 4 new phases of temporal coordination of STW, within a semistandardized set-up, in persons with stroke and in controls. The high degree of variability regarding relative STW phase duration was probably a result of both the semistandardized set up and biological variability. The significant difference in the transition phase across the 2 groups requires further study.

  • 4.
    Han, Mengjie
    et al.
    Dalarna University, School of Technology and Business Studies, Microdata Analysis.
    Zhang, Xingxing
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Xu, Liguo
    May, Ross
    Pan, Song
    Wu, Jinshun
    A review of reinforcement learning methodologies on control systems for building energy2018Report (Other academic)
    Abstract [en]

    The usage of energy directly leads to a great amount of consumption of the non-renewable fossil resources. Exploiting fossil resources energy can influence both climate and health via ineluctable emissions. Raising awareness, choosing alternative energy and developing energy efficient equipment contributes to reducing the demand for fossil resources energy, but the implementation of them usually takes a long time. Since building energy amounts to around one-third of global energy consumption, and systems in buildings, e.g. HVAC, can be intervened by individual building management, advanced and reliable control techniques for buildings are expected to have a substantial contribution to reducing global energy consumptions. Among those control techniques, the model-free, data-driven reinforcement learning method seems distinctive and applicable. The success of the reinforcement learning method in many artificial intelligence applications has brought us an explicit indication of implementing the method on building energy control. Fruitful algorithms complement each other and guarantee the quality of the optimisation. As a central brain of smart building automation systems, the control technique directly affects the performance of buildings. However, the examination of previous works based on reinforcement learning methodologies are not available and, moreover, how the algorithms can be developed is still vague. Therefore, this paper briefly analyses the empirical applications from the methodology point of view and proposes the future research direction.

  • 5.
    Åberg, Anna Cristina
    et al.
    The Swedish School of Sport and Health Sciences, Box 5626, SE-114 86 Stockholm, Sweden ; Department of Public Health and Caring Sciences/Geriatrics, Uppsala University, Uppsala Science Park, SE-751 85 Uppsala, Sweden.
    Elmgren Frykberg, Gunilla
    Uppsala universitet, Rehabiliteringsmedicin.
    Halvorsen, Kjartan
    Uppsala universitet, Reglerteknik; Swedish School of Sport and Health Sciences, Stockholm, Sweden.
    Medio-lateral stability of sit-to-walk performance in older individuals with and without fear of falling2010In: Gait & Posture, ISSN 0966-6362, E-ISSN 1879-2219, Vol. 31, no 4, p. 438-443Article in journal (Refereed)
  • 6.
    Åberg, Anna Cristina
    et al.
    The Swedish School of Sport and Health Sciences, Stockholm, Sweden ; Department of Public Health and Caring Sciences/Geriatrics, Uppsala, Sweden.
    Thorstensson, Alf
    The Swedish School of Sport and Health Sciences, Stockholm, Sweden.
    Tarassova, Olga
    The Swedish School of Sport and Health Sciences, Stockholm, Sweden.
    Halvorsen, Kjartan
    Uppsala universitet, Avdelningen för systemteknik ; School of Technology and Health, KTH-Royal Institute of Technology, Stockholm, Sweden.
    Calculations of mechanisms for balance control during narrow and single-leg standing in fit older adults: a reliability study2011In: Gait & Posture, ISSN 0966-6362, E-ISSN 1879-2219, Vol. 34, no 3, p. 352-357Article in journal (Refereed)
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