Tom Incledon, M.S. and Jose Antonio, Ph.D. and colleagues from the University of Nebraska, Kearney, NE, have published the first study to evaluate the effects of methoxyisoflavone supplementation on training adaptations. In this study, 14 healthy resistance-trained men were administered a placebo or a supplement containing 800 milligrams per day of methoxyisoflavone for eight weeks. Subjects were instructed to maintain their normal dietary intake and training volume throughout the study.
Prior to and following supplementation, subjects performed a vertical jump test to assess lower extremity peak force. In addition, bone density and body composition measurements were determined using dual energy X-ray absorptiometry (DEXA). There were no differences in initial peak force or body composition measurements between the groups prior to supplementation. Supplementation during training did not significantly affect changes in pre to post values in body weight, body mass index, bone mineral content, or peak force between groups. Subjects in the placebo group experienced a significant increase in body fat (pre 16.8, post 17.6 kg) while fat mass was unchanged in the methoxyisoflavone group (pre 18.7, post 17.3 kg). Muscle mass increased in the methoxyisoflavone group (pre 66.0, post 67.3 kg) but was not changed in the placebo group (pre 68.3, post 68.4 kg). As a result, subjects in the methoxyisoflavone group observed a slight decrease in percent body fat (pre 20.1, post 18.8) while subjects in the placebo group experienced a significant increase in percent body fat (pre 18.0, post 18.7 kg).