Association between relative free-living sit-to-stand transition thigh angular velocities and difficulties in mobility and daily functioning.

Participants with any functional difficulties performed free-living sit-to-stand transitions at a higher proportion of their STS capacity compared to those without difficulties.

• The study included 230 individuals (53% women) aged 79-89 years.
• 47% had ADL/IADL difficulties, 26% reported walking difficulties, and 17% had difficulties negotiating stairs.
• Differences in relative free-living STS thigh angular velocity between those with and without difficulties were statistically significant (p < 0.05) as assessed by Wilcoxon rank-sum test.
• STS capacity was assessed with an instrumented five-times STS test, and free-living STS transitions were monitored in 2-hour intervals over four days using an accelerometer.

Higher relative free-living STS thigh angular velocity was associated with walking difficulties in both crude and adjusted logistic regression models.

• Crude odds ratios ranged from 1.23 to 1.53 (p < 0.05) across difficulty outcomes.
• Adjusted odds ratios ranged from 1.20 to 1.40 (p < 0.05) for walking and stair negotiation difficulties.
• The association with walking difficulties remained statistically significant after covariate adjustment.

Higher relative free-living STS thigh angular velocity was associated with stair negotiation difficulties in both crude and adjusted models.

• Crude odds ratios for stair negotiation difficulties fell within the range of OR 1.23–1.53 (p < 0.05).
• Adjusted odds ratios for stair negotiation difficulties fell within the range of OR 1.20–1.40 (p < 0.05).
• 17% of the sample reported difficulties negotiating stairs.

The association between higher relative free-living STS thigh angular velocity and ADL/IADL difficulties weakened after adjustment for covariates.

• In crude models, higher relative STS velocity was associated with ADL/IADL difficulties (OR 1.23–1.53; p < 0.05).
• After adjustment, the association with ADL/IADL difficulties was no longer statistically significant.
• 47% of participants had ADL/IADL difficulties.
• This contrasted with the associations for walking and stair negotiation difficulties, which remained significant after adjustment.

The study used a cross-sectional design measuring relative STS intensity by combining instrumented five-times STS testing with free-living accelerometer monitoring.

• STS capacity was assessed with an instrumented five-times STS test measuring thigh angular velocity.
• Free-living STS transitions were monitored using an accelerometer in 2-hour intervals over four days.
• Relative free-living STS thigh angular velocity was calculated as the ratio of free-living STS velocity to maximal STS capacity.
• The sample consisted of 230 individuals aged 79-89 years, 53% of whom were women.