Two and Four Weeks of β-Hydroxy-β-Methylbutyrate (HMB) Supplementations Reduce Muscle Damage Following Eccentric Contractions.

OBJECTIVE: This study investigated the effect of β-hydroxy-β-methylbutyrate (HMB) supplementation for either 2 or 4 weeks on the muscle damage after elbow flexors after eccentric contractions (ECCs).

METHODS: Twenty-eight untrained men were completed the double-blind, placebo-controlled, parallel design study. The subjects were randomly assigned to the ingestion of HMB supplement for 2 weeks (HMB 2-week, n = 10), for 4 weeks (HMB 4-week, n = 10), or a placebo group (PL, n = 8). Subjects of HMB 2-week and HMB 4-week consumed 3 g HMB per day, and they performed 6 sets of 10 ECCs at 100% maximal voluntary contraction (MVC) using a dumbbell. Changes in MVC torque, range of motion (ROM), upper arm circumference, muscle soreness, and muscle stiffness were assessed before, immediately after, and 1, 2, and 5 days after exercise.

RESULTS: MVC torque and ROM were significantly higher in the HMB 2-week and HMB 4-week groups than in the PL group after ECCs (p < 0.05). The upper arm circumference was significantly smaller in the HMB 2- and 4-week groups than in the PL group after ECCs (p < 0.05). In addition, muscle stiffness at 150° was significantly lower in the HMB 2- and 4-week groups than in the PL group at immediately after ECCs (p < 0.05). However, there was no difference in all outcomes between HMB 2-week and HMB 4-week.

CONCLUSION: We concluded that more than 2 weeks of HMB supplementation has a positive role for untrained subjects to prevent the muscle damage after ECCs.