A recent study at the Baylor University's Exercise & Sport Nutrition Laboratory (ESNL) investigated whether some supposed "muscle-building" supplements, namely methoxyisoflavone, 20-hydroxyecdysone and sulfo-polysaccharide, affect training adaptations and/or markers of muscle anabolism/catabolism. Forty-five male gym rats were matched according to fat-free body mass and randomly assigned to ingest in a double-blind manner either an inactive fake supplement, 800 milligrams per day of methoxyisoflavone, 200 milligrams per day of 20-hydroxyecdysone or 1,000 milligrams per day of sulfo-polysaccharide for eight weeks during training. At zero, four and eight weeks, the subjects donated blood samples and completed comprehensive muscular strength (bench press and leg press), muscular endurance, anaerobic capacity and body composition analysis. What happened? Well, the results strongly suggest that these "muscle-building" supplements are absolutely useless. In other words, the investigators reported that these products didn't affect anabolic/catabolic markers (e.g., cortisol), body composition or training adaptations. Thus, I feel you shouldn't spend any money on such products. Stick with proven sports supplements, such as Creatine monohydrate, leucine and beta-alanine.

Reference: Wilborn CD et al. Effects of Methoxyisoflavone, Ecdysterone, and Sulfo-Polysaccharide Supplementation on Training Adaptations in Resistance-Trained Males. Journal of the International Society of Sports Nutrition. 3(2): 19-27, 2006.