Low‐Dose Lemon Myrtle Supplementation Enhances Muscle Hypertrophy in Older Adults Undergoing Low‐Load Resistance Training: A Randomized Controlled Trial

Background/Objectives Our previous study showed that a combination of lemon myrtle (LM) leaf extract at the conventional dose (250 mg/day, 2.5 mg/day as casuarinin) and low‐load resistance training using body weight led to significantly greater increases in muscle size than resistance training alone. This study aimed to determine whether LM supplementation at half the conventional dose (125 mg/day, 1.25 mg/day as casuarinin), combined with low‐load resistance training, could similarly enhance muscle hypertrophy in older adults and to evaluate the persistence of these effects during a detraining period. Methods This was a randomized, placebo‐controlled, double‐blind, parallel‐group trial. Sixty Japanese men and women aged ≥ 65 years who were aware of age‐related declines in muscle strength participated. Participants were randomly assigned to a placebo group or an LM group (receiving 125 mg/day). Both groups performed low‐load, bodyweight resistance training twice weekly (three sets of four exercises). Anterior thigh muscle thickness was assessed before and after the 12‐week intervention, and after a subsequent 6‐week detraining period. Results The LM group showed a significantly greater increase in anterior thigh muscle thickness than the placebo group. However, LM supplementation did not help maintain muscle hypertrophy during the detraining period. Conclusions LM supplementation at half the conventional dose enhances skeletal muscle hypertrophy following 12 weeks of low‐load resistance training in older adults experiencing muscle strength decline. Trial Registration: UMIN Clinical Trials Registry: UMIN000054801