Special Issue Article Movement analysis of sit-to-stand – research informing clinical practice Gunilla E. Frykberg 1,2 , Charlotte K. Ha ¨ger 2 1 Department of Neuroscience, Rehabilitation Medicine, Uppsala University, Sweden, 2 Department of Community Medicine and Rehabilitation, Physiotherapy, Umea ˚ University, Sweden Background: Sit-to-stand (STS) is a crucial transfer influencing a person’s independence in daily activities, as well as safety and quality of life, and is thus vital to evaluate in research and in practice. Clinical STS tests provide single values in seconds or numbers of STS. There is, however, increasing numbers of research papers reporting spatial and temporal kinematic and kinetic process STS data. Objectives: To provide an overview of research findings from laboratory-based movement analyses regarding phases and determinants of typical STS, characteristics of successful versus failed STS trans- fers, and finally STS performance in some neurological conditions. Major Findings: The STS transfer, previously regarded as mainly requiring lower limb muscle strength, is increasingly recognized as a complex transfer skill. Muscle strength, balance, foot position, chair height and the movement strategy are major determinants influencing STS performance. Scaling and timing of momentum generation throughout STS seems critical for success or failure. Sit-to-stand in stroke and Parkinson’s disease (PD) is characterized by asymmetry in force generation and difficulties in switching movement direction, respectively. In-depth, knowledge regarding mechanisms of momentum control during STS sub-phases, STS failures, as well as exploration of variability in normal and atypical STS is still lacking. Conclusions: Recent research based on instrumented movement analyses has generated better understanding of movement control during STS, but the specifics are not yet reflected in clinical assessments. There seems to be a call for clinical tools capturing determinants and process characteristics of the STS transfer for a more com- prehensive evaluation in rehabilitation. Keywords: Sit-to-stand, Movement analysis, Momentum control, Kinematics, Kinetics Background Rising to stand from a seated position (sit-to-stand, STS) is a very common task in daily life, and vital for independence in persons with disability. 1 Non-dis- abled adults perform STS about 60 times per day. 2 The importance of STS is particularly evident when the ability deteriorates and manifests itself as decreased mobility-related quality of life 3 and increased risk of falls in the elderly 4,5 as well as in per- sons with disabilities, e.g., after stroke. 6 Further, STS performance may contain prognostic information, e.g., in persons with chronic obstructive pulmonary disease (COPD). 7 In addition, outcomes of STS tests have proven to be strongly correlated with those from tests of exercise capacity, e.g., the 6-minute walk test. 8 Thus, STS is a crucial everyday transfer task and, as such, important to evaluate in clinical practice as well as in research. From a biomechanical point of view, STS may be defined as a transitional movement from sitting to upright standing posture, thus requiring horizontal and vertical displacement of the whole body’s centre of mass (COM) from a stable to a less stable position over extended lower extremities. 9 Table 1 summarises some biomechanical concepts 9,10 central to research addressing STS using laboratory-based movement analysis, included here to clarify and assist in reading this paper. From such a perspective, it is natural to approach the understanding of STS in terms of how forces and movements are generated and controlled by the brain and how the resulting movement par- ameters might be captured with technical devices. In clinical practice, on the other hand, STS ability is assessed through performance-based tests, which either report the time it takes to do five or 10 rep- etitions or the number of repetitions being conducted during 20 or 30 seconds or 1 minute, i.e., a single value represents the end result of the task. The five times sit-to-stand test (FTSST) seems to be the most frequently used STS protocol 11 and this well Correspondence to: Gunilla E. Frykberg, Department of Neuroscience, Rehabilitation Medicine, Uppsala University, Uppsala SE-751 85, Sweden. Email: gunilla.elmgren.frykberg@neuro.uu.se 156 ß W. S. Maney & Son Ltd 2015 DOI 10.1179/1743288X15Y.0000000005 Physical Therapy Reviews 2015 VOL. 20 NO.3