Effects of Leucine Ingestion and Resistance Training on Body Composition and Strength in Older Individuals

PURPOSE: To examine the effects of ingesting free leucine on training-induced changes in body composition and muscle strength in older males. METHODS: Twenty three non-resistance trained males (61.22 ± 7.13 yrs, 176.93 ± 5.99 cm, 92.59 ± 14.59 kg) were randomized in a double blind manner. Participants ingested either leucine (LEU) [3g/d LEU + 5g carbohydrate (CHO)] or maltodextrose (CHO) (5g/d CHO) while participating in a supervised high intensity resistance training program (3 sets × 10 repetitions at 75% of 1RM), 3 days per week for 12 weeks. Testing sessions were completed prior to, 4 weeks, 8 weeks and 12 weeks post resistance training and supplementation. Each testing session included muscle strength measurement as determined by 1 repetition maximum (RM) on leg press and bench press. Data was analyzed using repeated measures ANOVA. RESULTS: A significant time effect was observed for 1RM bench press (0 weeks: 61.7 ± 17.2 kg vs. 12 weeks: 82.7 ± 23.1 kg, p < 0.001), 1 RM leg press (0 weeks: 261.6 ± 81.4 kg vs. 12 weeks: 392.4 ± 129.9 kg, p < 0.001), body weight (0 weeks: 92.59 ± 14.59 kg vs. 12 weeks: 93.56 ± 14.92 kg, p < 0.05) and fat free mass (0 weeks: 58.41 ± 9.13 kg vs. 12 weeks: 59.69 ± 8.98 kg, p< 0.01). A significant group by time interaction was observed for both 1RM bench press and leg press (p < 0.001), with subsequent analysis revealing significantly higher 1RM leg press strength in the LEU group compared to the CHO placebo at 12 weeks (LEU: 464.1 ± 145.7 kg vs. CHO = 333.7 ± 81.7 kg, p<0.05), while only a trend for higher 1RM bench press strength was identified in the LEU group compared to the CHO placebo at 12 weeks (LEU: 92.9 ± 22.6 kg vs. CHO: 74.4 ± 20.9 kg, p = 0.063). CONCLUSION: The ingestion of free leucine with carbohydrate, as compared to carbohydrate alone, when combined with 12-weeks of high intensity resistance training may enhance muscle strength in older males.