A study of the effects of betaine – TMG, or trimethylglycine – on muscular power during cycling found that ingesting 2.5 grams of the dietary supplement betaine for 7 days before a series of cycling sprint tests increased several measures of performance power by about 5.5 percent compared to baseline and 3.5 percent compared to placebo.
The study involved 16 physically active subjects, and used a randomized, double-blind crossover design, with a three week washout between the second and third tests post-baseline. Results were thought to be statistically significant, with analysis yielding p values ranging from 0.007 for maximum peak power to 0.034 for average mean power. Tests on placebo did not differ from baseline.
Betaine is naturally found in beets as well as spinach, and is a methyl donor nutrient, biochemically involved in the body with other methyl donor nutrients such as vitamin B12, folate, choline, and SAM-e. It has been reported to lower homocysteine levels.
The discussion section of the research article, published in the Journal of the International Society of Sports Nutrition, mentions that betaine may contribute to intracellular creatine synthesis, but reasons that more likely the performance benefits of betaine are due to its effective osmolyte effects, which would help muscle cell survival and protein synthesis, as well as fostering ongoing myosin ATPase action during intense stress.
The full research article can be found online here:
Reference: J Luke Pryor, Stuart AS Craig, Thomas Swensen. Effect of betaine supplementation on cycling sprint performance. Journal of the International Society of Sports Nutrition 2012, 9:12. doi:10.1186/1550-2783-9-12.