Year of Publication

2015

Degree Name

Doctor of Philosophy (PhD)

Document Type

Doctoral Dissertation

College

Education

Department

Kinesiology and Health Promotion

First Advisor

Dr. Jody Clasey

Abstract

Supporters of a nutritional supplement, β-Hydroxy-β-Methylbutyrate (HMB) supplementation, claim that it will increase the muscular strength gains and lean muscle mass gains seen during a resistance training program. It has been suggested that HMB supplementation does this by preventing muscle damage or by regenerating damaged muscle cell membranes. However, no research has evaluated the effect of HMB supplementation on low frequency fatigue. Therefore, the purpose of this study was to determine if three weeks of HMB supplementation could attenuate the effects of low frequency fatigue caused by eccentric muscle contractions of the tibialis anterior muscle. A total of 33 healthy recreationally active subjects (18 males, 15 females; 23.2 ± 4.3 yr) were recruited for this study. All subjects preformed 4 sets of 25 eccentric contractions of the tibialis anterior muscle through a range of motion of 30 degrees. Recovery measures were taken for 20 minutes after the fatigue protocol and at 48 and 96 hours of recovery. The recovery measures included: Maximum voluntary contraction peak torque, 10 Hz peak torque, 50 Hz peak torque, 10/50 Hz peak torque ratio, and EMG measurements. Each subject served as their own control and limbs were randomly assigned to pre-supplement or post-supplement limbs. Following the pre-supplement fatigue protocol and recovery measures each subject completed three weeks of 3g/day HMB supplementation. After the supplementation period the post-supplement fatigue protocol was completed and recovery measures were taken. The 10 Hz peak torque and the 10/50 Hz torque ratio in the pre-supplement limb was still significantly reduced at the 96-hour recovery measurement time, indicating that it was still showing low frequency muscle fatigue at this time. Furthermore, the post-supplement limb, recovered from the fatigue protocol faster, and did not show any signs of low frequency muscle fatigue at the 48-hour recovery measurement time. In addition the pre-supplement limb had significant maximum voluntary contraction torque deficit at the 48-hour recovery measurement time and the post-supplement limb showed no significant deficits. The main findings of this study were that three weeks of HMB supplementation attenuated low frequency fatigue and maximum voluntary contraction torque reduction after an eccentric fatigue protocol.

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