Poster Topical Area: Sports Nutrition
Poster Board Number: 253
Objectives: β-hydroxy-β-methylbutyrate (HMB) has been shown to supply as the main component of the muscle cell membrane, cholesterol, and activate the signaling pathway of muscle protein synthesis through the mammalian target of rapamycin. Previously, HMB and α-ketoisocaproate for 2 weeks supplementation have been reported a significant effect on the muscle damage following a bout of eccentric contractions (ECC). On the contrary, since the study observed no effect on muscle damage after ECC in which HMB was ingested for 6 days prior ingestion, the effect of long term and single HMB supplementation on muscle damage after one bout of ECC is still unclear. Therefore, this study investigated the effect of 2 and 4- week HMB supplementation on ECC-induced muscle damage.
Methods: Twenty-eight healthy men were randomly assigned to consume the HMB supplement for 2weeks (HMB 2W, n = 10), 4 weeks (HMB 4W, n = 10), or placebo (PL, n = 8). HMB groups consumed 3 g HMB per day for 2 or 4 weeks prior to exercise and continued until 5 days after ECC. Subjects performed six sets of ten elbow flexors ECC using dumbbell at 100% MVC. Changes in the maximal voluntary isometric contraction (MVC) torque, range of motion (ROM), muscle soreness, and muscle shear elastic modulus were assessed before, immediately after, 1, 2, and 5 days after exercise. The shear elastic modulus was determined in biceps brachii at 70°, 110° and 150° of elbow angle on the damaged arm (Aixplorer version 4.2, Supersonic Imagine, France).
Results: MVC torque was significantly higher in HMB 2W and 4W than in PL at immediately and one day after exercise (p < 0.05). ROM was significantly greater in HMB 2W and 4W than in PL at 5 days after exercise (p < 0.05). In addition, ROM for HMB 4W was also significantly greater than that for PL at immediately after exercise (p < 0.05). No significant difference was observed between groups in muscle soreness. Muscle shear elastic modulus at 150°elbow angle was significantly lower in the HMB 2W and 4W than in the PL at immediately after exercise (p < 0.05). However, no significant difference was observed between HMB 2W and 4W in all parameters.
Conclusions: We concluded that HMB supplementation reduces eccentric exercise-induced muscle damage. Also, we suggest that there is no difference in the effect of HMB between 2 and 4 weeks.
Teikyo Heisei University
Nakano, Tokyo, Japan