Beta-hydroxy-beta-methylbutyrate Supplementation On Low-frequency Fatigue Following Fatiguing Exercise

Abstract

Participation in any strenuous form of physical activity will result in a decline in skeletal muscle performance during and following the activity, this decline is commonly called fatigue. Low-frequency fatigue (LFF), a form of fatigue, is characterized by a loss of force at low frequencies of stimulation, a slow recovery of force and is reported following eccentric contractions. β-Hydroxy-β-Methylbutyrate (HMB) is a nutritional supplement that claims to prevent and improve skeletal muscle recovery following muscle damage producing contractions. PURPOSE: To determine if three weeks of HMB supplementation could attenuate the effects of LFF caused by eccentric muscle contractions in young healthy adults. METHODS: 33 participants (18 males, 15 females; 23.2 ± 4.3 yr.) completed the study. Participants performed 4 sets of 25 eccentric (ECC) contractions of the tibialis anterior muscle. Outcome measures were recorded prior, following, throughout a 20-minute recovery period, and at 48 and 96 hours following an ECC fatiguing protocol. Outcome measures included: isometric peak torque, 10 and 50 Hz peak torque, and 10/50 Hz peak torque ratio. Participants served as their own control and lower limbs were randomly assigned as control (CTL) or supplement (SUP). Following the pre-supplement test-day, participants completed 3 weeks of 3g/day of HMB supplementation. Post-supplementation, the ECC fatiguing protocol was completed and outcome measures were obtained. RESULTS: The ECC fatiguing protocol reduced isometric peak torque in both the CTL and SUP limbs by 49.3% and 48.4%, respectively (p<0.01).Ten Hz peak torque (pre-ECC fatigue: 4.8±2.2 Nm vs. 96-hr post-ECC fatigue: 4.2±2.4 Nm) and the 10/50 Hz peak torque ratio (pre-ECC fatigue: 0.51±0.14 vs. 96-hr post-ECC fatigue: 0.44±0.14) in the CTL limb were reduced at the 96-hour time point (p<0.01), indicative of LFF. The SUP limb displayed no LFF (pre-ECC fatigue: 0.49±0.11 vs. 48-hr post-ECC fatigue: 0.47±0.11) at the 48-hour time point (p>0.05), suggestive of a faster recovery. The CTL limb showed a 19.2% reduction in isometric peak torque at the 48-hour recovery time point (p<0.01); whereas, the SUP limb displayed only a 6.4% reduction in isometric peak torque. CONCLUSIONS:Three weeks of HMB supplementation attenuated LFF and force loss after an ECC fatigue protocol.