Estimation of Functional Reserve in Patients with Hospital-Associated Deconditioning

Background: This study aimed to analyze the applicability of sit-to-stand (STS) muscle power tests for evaluating functional reserve in patients with hospital-associated deconditioning (HAD). Methods: This study is a single group preliminary observational study. STS tests were performed in the early stages of comprehensive rehabilitation treatment, and the interval changes in the clinical indicators were assessed after four weeks of clinical observation. A STS capacity ratio was estimated by the time duration of five STS repetitions (5r-STS) and the maximum number of STS repetitions over 30 s (30s-STS); the activities were measured using a three-dimension motion capture system and force plate. Results: After 4 weeks of comprehensive rehabilitation, the 10 m gait speed (p = 0.004), hand grip power (p = 0.022), hip extensor power (p = 0.002), Berg balance scale (p < 0.001), and modified Barthel index (MBI) (p = 0.001), respectively, were significantly improved. The force plate-derived (FPD) 30s-STS power and the number of repeats in the FPD 30s-STS showed a positive correlation with improvements in the hand grip power (Spearman’s Rho = 0.477, p = 0.045), hip extensor power (Spearman’s Rho = 0.482, p = 0.043), and MAI (Spearman’s Rho = 0.481, p = 0.043), respectively. The STS capacity ratio was correlated with higher improvements in the 10 m gait speed (Spearman’s Rho = 0.503, p = 0.034), hip extensor power (Spearman’s Rho = 0.494, p = 0.037), and MBI (Spearman’s Rho = 0.595, p = 0.009). Despite individual variability in the differences between the FPD and estimated STS power, the results for the correlation between the STS capacity ratio and clinical outcomes were consistent. Conclusions: The STS capacity ratio showed a positive correlation with the clinical outcomes, including gait speed, and may reflect a part of the functional reserve excluding the individual variability of performance.