The Role of Dietary Protein Intake and Resistance Training on Myosin Heavy Chain Expression

Colin D Wilborn, Darryn S Willoughby

During resistance training the muscle undergoes many changes. Possibly the most profound and significant changes are those that occur in the muscles contractile proteins. Increases in these contractile proteins are one of the primary factors contributing to myofibrillar hypertrophy. The most abundant muscle protein is myosin, which comprises 25% of the total muscle protein. Due to the large amount of skeletal muscle that is composed of myosin, changes in this fiber may have profound effects on skeletal muscle size and strength. The myosin molecule is made up of 6 subunits, 2 very large heavy chains, and 4 smaller light chains. The myosin heavy chain (MHC) accounts for 25-30% of all muscle proteins making its size an important factor in skeletal muscle growth. In conjunction with resistance training, dietary protein intake must be adequate to illicit positive adaptations. Although many studies have evaluated the role of dietary protein intake on skeletal muscle changes, few have evaluated the MHC specifically. Research has clearly defined the need for dietary protein and resistance training to facilitate positive changes in skeletal muscle. The purpose of this review was to evaluate the current literature on the effects of dietary protein and resistance training on the expression of the myosin heavy chain.