Validity of linear encoder measurement of sit-to-stand performance power in older people

Abstract Objective To investigate construct validity of linear encoder measurement of sit-to-stand performance power in older people by showing associations with relevant functional performance and physiological parameters. Design Cross-sectional study. Setting Movement laboratory of a geriatric rehabilitation clinic. Participants Eighty-eight community-dwelling, cognitively unimpaired older women (mean age 78 years). Main outcome measures Sit-to-stand performance power and leg power were assessed using a linear encoder and the Nottingham Power Rig, respectively. Gait speed was measured on an instrumented walkway. Maximum quadriceps and hand grip strength were assessed using dynamometers. Mid-thigh muscle cross-sectional area of both legs was measured using magnetic resonance imaging. Results Associations of sit-to-stand performance power with power assessed by the Nottingham Power Rig, maximum gait speed and muscle cross-sectional area were r = 0.646, r = 0.536 and r = 0.514, respectively. A linear regression model explained 50% of the variance in sit-to-stand performance power including muscle cross-sectional area ( p = 0.001), maximum gait speed ( p = 0.002), and power assessed by the Nottingham Power Rig ( p = 0.006). Conclusions Construct validity of linear encoder measurement of sit-to-stand power was shown at functional level and morphological level for older women. This measure could be used in routine clinical practice as well as in large-scale studies. Clinical Trial Registration Number DRKS00003622.