Differences in power and performance during sit-to-stand test and its relationships to functional measures in older adults with and without Parkinson's disease

i) to compare 30-s sit-to-stand (STS) test repetitions and power between older adults with and without Parkinson's disease (PD) and ii) to evaluate the relationship of STS repetitions and power with functional measures in older people with PD. STS repetitions and power (Alcazar's equation) during the 30-s STS test were assessed in forty-six age- and sex-matched older adults with and without PD. Functional measures included habitual (HGS) and maximum gait speed (MGS), timed-up-and-go (TUG) test and the Mini-Balance Evaluation System Test (Mini-BEST). PD-specific tests were as follows: the motor subscale of the Unified Parkinson's Disease Rating Scale (UPDRS-III), quality of life [Parkinson's Disease Questionnaire (PDQ-39)], perceived freezing of gait (FOG questionnaire), and fear of falling [Falls Efficacy Scale (FES)]. T scores, repeated measures ANOVA and linear regression analyses were used. T scores for older adults with PD were − 2.7 ± 4.5 for STS repetitions, −5.2 ± 4.2 for absolute STS power, and − 3.1 ± 4.6 for relative STS power compared to older adults without PD. T scores for absolute STS power were lower than T scores for STS repetitions ( p  < 0.001) and relative STS power ( p  < 0.001). Both absolute and relative STS power and STS repetitions showed similar correlations with functional measures ( r  = 0.44 to 0.59; both p  < 0.05). Relative STS power ( r  = −0.55; p  < 0.05) and STS repetitions ( r  = −0.47 to −0.55; p  < 0.05) but not absolute STS power were correlated to PD-specific tests. STS repetitions and power values estimated through the 30-s STS test were lower in older people with PD than without PD. Overall, STS power measures were similarly associated with functional performance as STS repetitions, indicating these power equations can be implemented when assessing lower extremity function in older people with PD.