Abstract
Sarcopenia in older adults increases fall risk and frailty. Improving muscle mass and function enhances balance and supports basic activities of daily living. Leucine-enriched essential amino acid supplementation combined with resistance training has been shown to enhance muscle performance. The present study evaluated muscle performance outcomes after 6 mo of these treatments. In an open-label randomized controlled trial, 66 participants were randomized equally to control and intervention groups (n = 33 each). Both groups consumed daily leucine-enriched essential amino acid supplements after exercise. The intervention group performed resistance training, and the control group followed regular walking and strengthening exercises. Primary outcomes were appendicular skeletal muscle mass index (ASMI), gait speed, and hand grip strength. Safety was assessed by adverse event reporting and laboratory tests. The results of this study show no significant improvement in ASMI in either group after 6 mo. Both groups demonstrated significant gait speed improvements, with no between-group difference. Hand grip strength improved only in the non-dominant hand of the control group. No serious adverse events occurred, and kidney function remained stable. In conclusion, 6 mo of daily leucine-enriched essential amino acid supplementation combined with exercise did not increase ASMI among healthy older adults. Gait speed showed a positive association with supplementation and daily exercise regardless of regimen. Improvement in hand grip strength was observed only in the non-dominant hand, warranting further investigation to clarify the effect of supplementation combined with exercise. Additional clinical studies are required to establish the effectiveness of this regimen in preserving muscle mass and enhancing functional performance. Clinical trial registration: This study has been registered with the Thai Clinical Trials Registry (ID: TCTR20210824002).