Nutrition and Injury Prevention
Inadequate glycogen repletion causes a reliance on fat and protein stores and this may result in increased protein break-down, which, in turn, may lead to soft tissue injury. There are several mechanisms by which inadequate dietary protein intake may lead to muscle injury. Intense training classes causes skeletal muscle breakdown, which can be exacerbated by inadequate dietary protein. Inadequate hydration may compromise blood flow to working muscle, which may increase susceptibility to injury. Hydration is thought to influence the amount and composition of joint fluid, which helps to nourish articular cartilage.
Glycogen is the major energy source for muscular activity. Training depletes muscle and liver glycogen stores. Repetitive bouts of activity can cause profound glycogen depletion and impair sporting performance.
The aim of high-carbohydrate diet is to restore glycogen levels to normal within 24 hours of strenuous exercise. The type, amount and timing of carbohydrate ingestion influences glycogen replenishment.
Intense exercise results in breakdown of muscle tissue. Intake of protein recovery meals is recommended to enhance net protein balance, tissue repair and adaptations involving synthesis of new proteins.
The co-ingestion of protein with carbohydrate will increase the efficiency of muscle glycogen storage when the amount of carbohydrate ingested is below the threshold for maximum glycogen synthesis or when feeding intervals are more than 1 hour apart. The effectiveness of protein to enhance muscle glycogen storage appears limited to the first hour after supplementation. It has been shown that glycogen store during the first 40 minutes of recovery after exercise was twice as fast after a carbohydrate- protein feeding than after isoenergetic carbohydrate feeding, and four times faster than a carbohydrate feeding of the same carbohydrate concentration. This trend also continued following the second feeding 2 hours into recovery. These results have important implications for sports when very short recovery periods during competition, such as soccer and ice hockey.
The consumption of excessively large amounts of protein ad fat in an athlete’s diet is discouraged because they may displace carbohydrate foods within the athlete’s energy requirements and affect gastric comfort, thereby indirectly interfering with glycogen storage by preventing adequate carbohydrate intake.