Abstract
The leusine metabolite beta-hydroxy-beta-methylbutyrate (HMB) has been shown to increase muscle mass and strength following resistance training and has been also proposed to function as an anticatabolic agent and decrease exercise induced muscle damage. PURPOSE: The aim of this study was to investigate the effects of 14 days oral supplementation of HMB on muscle damage as a result of intense and prolonged uphill and downhill running. METHODS: Subjects (n=22) well trained endurance runners were randomly assigned to treatment of either HMB (3g/day) or a placebo for 2 weeks before race. They all run Olympus mountain marathon (44km) consisted of 21km uphill to 2700m altitude and 23km continuous downhill. Venous blood samples were obtained from the participants before, immediately after the race, also 3 and 7 days post race. They were analysed with standard methods for creatine phosphokinase (CPK), lactate dehydrogenase (LDH) and myoglobin (MGL). RESULTS: Mean±sd (n=22) pre race CPK (149.55±21.47 U/L), MGL (32.31±4.00 mcg/l) and LDH (327.27±34.43 U/L) increased 5 (714.06±203.02U/L), 20 (662.06±260.99mcg/l) and 2 (698.06±107.84 U/L) fold (p<0.01) respectively immediately after the race. Mean CPK (256.93 U/L), MGL (61.64 mcg/l) and LDH (467.21 U/L) activities remained elevated 1.7, 1.9, and 2.1 fold (p<0.05) respectively 72 hours after the race. The placebo-supplemented group exhibited significantly greater (p<0.05) plasma concentration of CPK, LHD and MGL post race, 3 days and 7 days after the race than did the HMB supplemented group. Placebo-supplemented group presented also greater (p<0.05) mean difference (post race minus pre race values) in muscle damage biomarkers. CONCLUSIONS: The results of this study indicate that 2 weeks dietary supplementation of 3.0g HMB/day in endurance runners resulted in decreased CPK, LDH and MGL, after a very prolonged run. The finding agree with the hypothesis that HMB supplemented athletes experienced less muscle damage and also recovered at a faster rate.
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