Background: This study aimed to determine the threshold of muscle power and strength enhancements that lead to functional gains after exercise intervention in an acute care unit.

Methods: A total of 302 older patients (

Intervention: 169, control: 133) from 2 randomized clinical trials were included (mean age: 86.7 years). We measured maximal strength (1RM) and muscle power via a velocity transducer during leg press exercise at 30% and 60% of 1RM. A multicomponent exercise program, including power training, balance, and gait exercises performed over 3 to 6 consecutive days, served as the intervention. We used an anchor-based method to correlate muscle function increases with the Short Physical Performance Battery (SPPB) and gait velocity (GVT) to define clinically meaningful improvements.

Results: In the intervention group, marked differences were found in maximal power at 30% of 1RM between SPPB responders and nonresponders (relative 83.5% vs 34.8%; absolute 33.0 vs 12.8 W; p < .05) and at 60% of 1RM (relative 61.1% vs 22.4%; p < .05). GVT responders demonstrated significantly greater improvements in both relative and absolute maximal power than nonresponders at both 30% and 60% of 1RM (p < .05), as well as greater absolute 1RM gains (21.2 vs 15.2 kg, p < .05). Clinically meaningful improvements for muscle power based on SPPB and GVT ranged from 30.2% to 48.7%, whereas for 1RM, it was 8.2% based on GVT.

Conclusions: Muscle power gains were most notable in patients with improvements in the SPPB and GVT, highlighting the critical role of muscle power in functional recovery in these patients.