Journal Title (Medline/Pubmed accepted abbreviation): J Strength Cond Res
Page numbers: 2235-2241
Summary of background and research design:
Background: Betaine may serve as a methyl donor in the production of creatine and phosphatidylcholine. In doing so, betaine may enhance muscle strength and power performance (creatine) and/or increase reaction times and focus with decreased fatigue (phosphatidylcholine). Clinical evidence is conflicting both for the importance of methyl donation to creatine synthesis and for enhanced performance during short-term betaine supplementation.
Hypothesis/Purpose: The purpose of this study was to evaluate the efficacy of short-term betaine supplementation on concentric (CON) and eccentric (ECC) force outputs, fatigue, and muscle soreness ratings in men.
Subjects: Eleven men participated in this study (mean age, 21.7 ± 5.1 y; height, 178.5 ± 6.4 cm; body mass, 79.8 ± 10.3 kg; body fat percentage, 11.0% ± 1.4%).
Experimental design: Randomized, cross-over
Treatments and protocol: Men were randomized to once-daily betaine (2.5 g in 500 mL sports drink) or placebo (sports drink alone) supplementation for 15 days, during which isokinetic testing using a multiple-joint isokinetic dynamometer (chest press) was performed 5 times separated by 72 hours. Following a 4-week no-supplementation period and once-weekly dynamometer workout, the opposite supplementation was administered with the identical testing routine. Peak CON testing was a maximal push, and peak ECC testing was maximal resistance to the dynamometer arm. This was followed by 5 sets of 6 reps each at 80% peak, with 2-minute rest intervals. Fatigue and muscle soreness were rated after each testing using a 15-cm visual analog scale.
Summary of research findings:
- No significant differences were observed in peak CON force output between the betaine and placebo groups.
- Betaine (pre vs. post): 335.9 ± 78.3 vs 330.3 ± 74.8 N.
- Placebo (pre vs. post): 321.6 ± 63.6 vs 330.2 ± 71.6 N.
- No significant differences were observed in peak ECC force output between the betaine and placebo groups.
- Betaine (pre vs. post): 352.0 ± 90.6 vs 353.2 ± 98.2 N.
- Placebo (pre vs. post): 324.4 ± 85.2 vs 366.9 ± 128.5 N.
- Mean CON and ECC results were similar to the peak results.
- Subjective measures of fatigue and muscle soreness were not different between the 2 groups.
- However, the fatigue score was reduced over time in the betaine group, while there was no change in the placebo group (P < .05).
Interpretation of findings/Key practice applications:
In this study, betaine supplementation did not affect isokinetic force output or the quality of the workout and, therefore, does not support the ergogenic benefits reported by previous studies. The type of testing in this study (isokinetic relative to daily change), which was different from previous studies (constant resistance related to baseline), may have contributed to the contrasting results observed. Additionally, a longer supplementation period may be necessary to observe isokinetic benefit. The potential benefit on fatigue requires further research.