The results were presented at a meeting of the American Physiological Association in San Diego.
Whey protein is a naturally occurring dairy protein found in cow's milk. Whey isolate is the highest quality form of whey that is extracted and purified during the cheese-making process. Other studies have shown the nutritional properties of whey protein to be promising. Creatine is already popular among athletes looking for a competitive edge.
One earlier rat study showed that a creatine-plus-whey protein formulation significantly increased levels of muscle force and cellular energy production. The supplement also produced significantly better improvements in strength and body composition in bodybuilders during resistance training, according to a news release.
In the current study, 33 athletes were matched for strength prior to the study and then separated into one of four groups: those taking a creatine-carbohydrate supplement, whey protein isolate, whey protein isolate-creatine, or a carbohydrate-only supplement. Researchers measured number of muscle fibers by biopsy, strength, and lean mass in 33 athletes before and after 11 weeks of resistance training.
While all groups had increases in strength, lean mass, and muscle fibers, the whey protein plus creatine group had the greatest increases in all areas, reports Mick Carey, PhD, a researcher with the Center for Rehabilitation in Exercise and Sport Science at Victoria University in Australia. The research was supported by AST Sports Science.
The whey protein-creatine supplement group also had significantly greater increases in fast-twitch muscle fibers than did men consuming an equivalent calorie-containing supplement.
The fast-twitch muscle fibers are responsible for maximal force production and muscle growth in response to resistance training. There was an especially significant correlation between the magnitude of strength gained in three weight-lifting exercises and the increase in size of all muscle fiber types.