JMIR Publications

ABSTRACT

Background:

Sarcopenia and age-related declines in muscle function threaten independence and increase falls risk in community dwelling older adults. Muscle strengthening exercise delivered via mobile health (mHealth) apps could help address access barriers, but scalable programs require valid remote assessments of lower limb function. The five times sit to stand test (5TSTS) is a well established indicator of lower limb strength and functional capacity, yet its validity in asynchronous, smartphone video formats remains unclear.

Objective:

To examine agreement, reliability, and concurrent validity of a smartphone recorded, asynchronously scored 5TSTS compared with laboratory 5TSTS and isokinetic knee extensor strength in community dwelling older adults.

Methods:

Thirty-four older adults aged >60 years attended a single laboratory visit for isokinetic dynamometry of dominant limb knee extensors and standardized 5TSTS testing, then completed a home based 5TSTS after a >3 day wash out, recording the test on their own smartphone. Videos were timed offline by the lead author (EB) using video analysis software. Agreement between laboratory and remote 5TSTS was assessed using Bland Altman analysis and intraclass correlation coefficient (ICC); reliability and measurement error were quantified via ICC, coefficient of variation percentage (CV%), standard error of measurement (SEM), and minimal detectable change at the 95% confidence level MDC95. Pearson correlations examined associations between bodyweight normalized peak torque and both 5TSTS measures.

Results:

Twenty nine participants provided complete laboratory and remote data. Remote 5TSTS times were, on average, 0.3 s faster than laboratory values, with 95% limits of agreement −2.24 to 2.84 s. No obvious proportional bias was observed. Reliability metrics indicated good consistency (ICC = 0.89), good repeatability (CV = 7%), SEM = 0.9 s, and MDC95 = 2.5 s. Both laboratory and remote 5TSTS showed moderate negative correlations with normalized knee extensor torque, indicating that greater strength was associated with faster performance in both conditions.

Conclusions:

Asynchronous smartphone video 5TSTS demonstrates acceptable agreement with laboratory assessment, good reliability, and moderate concurrent validity with isokinetic knee extensor strength. This supports its use as a pragmatic remote tool for monitoring progress within mHealth muscle strengthening programs for community dwelling older adults. Clinical Trial: The study was pre-registered on the Open Science Framework (OSF), which included full details on study design, approach, and data analysis plan prior to the commencement of recruitment and data collection.