Effect of resistance training and lemon myrtle extract on muscle size of older adults: A pilot randomized controlled trial

Background: Recent studies have shown that lemon myrtle leaf (LM) extracts activate muscle satellite cells. This research examined the impact of combining LM extract supplementation with resistance training on muscle hypertrophy in older adults. Methods: This randomized controlled trial allocated fourteen older adults (65-79 years) to either an LM supplement group (n=7) or a placebo group (n=7). Participants engaged in low-load resistance training twice weekly for 12 weeks while receiving their designated supplements. Muscle thickness at the anterior thigh (AT) was assessed using B-mode ultrasound at baseline, 6 weeks, and 12 weeks to evaluate muscle hypertrophy. Trial registration: UMIN000050432. Results:.A 12-week intervention yielded significant muscle thickness enhancements in both groups. Nonetheless, the LM group exhibited a substantially greater relative increase (p < 0.05) compared to the placebo group. Furthermore, the low-load resistance training program elicited a significant 7.4% increase in muscle thickness in the LM group at six weeks, whereas the placebo group displayed a negligible 0.1% change. Conclusions: The present study suggests that intake of LM extract could enhance the muscle hypertrophy effect of resistance training and requires further investigation in the future. Keywords: sarcopenia, plant extract, muscle hypertrophy, lemon myrtle