Muscle endurance and quality of repetitions

This study examined the efficacy of 15 days of betaine supplementation on muscle endurance, power performance and rate of fatigue in active college-aged men. Male subjects (24) were randomly assigned to one of two groups; the first consumed betaine daily (2.5 g/d), and the second consumed a placebo. Subjects were tested prior to the onset of supplementation (T1) and 7 (T2) and 14 days (T3) following supplementation. Subjects were tested over a 2-day period for:

- vertical jump power (VJP)
- bench press throw (BPT) power
- number of squat repetitions at 75% 1-RM (peak and mean power)
- number of bench press repetitions at 75% 1-RM (peak and mean power)
- two 30-sec Wingate anaerobic power tests (WAnT) (Day 2)

There were no differences in power assessment (VJP, BPT, WAnT) between the groups, or in the repetitions performed to exhaustion or in the number of repetitions performed at 90% of both peak and mean power between the groups in the bench press exercise.

However, the number of repetitions performed in the squat exercise for BET was significantly greater (p < 0.05) than that seen for PL at T2. The number of repetitions performed at 90% or greater of peak power in the squat exercise was significantly greater for BET at both T2 and T3 than PL. It was concluded that either 1 or 2 weeks of betaine supplementation in active, college males improved muscle endurance of the squat exercise, and increased the quality of repetitions performed.

Hoffman et al (2009). "Effect of Betaine Supplementation on Power Performance and Fatigue." Journal of the International Society of Sports Nutrition 6(1): 7.