Cooke, Matthew (2005) The effects of nutritional supplementation on regeneration of muscle function after damage. PhD thesis, Victoria University.

Abstract

It is well established that following eccentric exercise (contractions during which muscles are actively lengthened) and myotoxic injection, disturbances in the regulation of intracellular calcium (Ca2+) homeostasis and increased rate of protein degradation will eventually lead to muscle damage (see Allen et al., 2005). Enhancing the rate at which muscles recover from injury may involve reducing the initial amount of damage by improving the intracellular Ca2+ handling ability of the muscle, or increasing the rate of regeneration by enhancing muscle protein synthesis. Two dietary supplements that may accomplish this are creatine monohydrate and whey protein. Thus, the purpose of this thesis was to examine the effects of creatine monohydrate and whey protein consumption on force recovery after eccentrically-induced muscle damage in healthy individuals. Moreover, to confirm these results by analysing force recovery in two parallel animal studies after controlled, chemically-induced injury. In addition, to determine the mechanisms by which creatine and whey protein exert their effects by examining morphological and biochemical properties of fast-twitch (extensor digitorum longus, EDL) and slow-twitch (soleus) rat skeletal muscle during recovery. In the human studies, muscle strength was significantly higher in the whey protein- and creatine-supplemented groups compared to those consuming a carbohydrate placebo following eccentrically-induced muscle damage. Lower plasma creatine kinase and lactate dehydrogenase levels in the days after injury was indicative of less muscle damage, and thus, supported the improved functional capabilities observed. In the animal studies, creatine supplementation significantly enhanced functional capacity of the regenerating EDL muscles by reducing the extent of fibre necrosis and augmenting fibre regeneration following myotoxic injury. These effects occurred as a direct result of increased muscle protein content, regenerating fiber CSA and muscle mass. Whey protein supplementation significantly enhanced functional capacity of the regenerating EDL muscles by reducing the extent of fibre necrosis following myotoxic injury. Similar to creatine supplementation, enhanced functional capacity of the EDL muscles was due to direct increases in muscle protein content, regenerating fiber CSA and muscle mass. However, in contrast to creatine supplementation, improved muscle recovery was only evident in the early stages of muscle regeneration, with no effects from whey protein supplementation observed in the later stages of muscle regeneration. Similarly, only limited effects were observed in the soleus muscles with either supplement. In conclusion, the results from this thesis have shown the creatine monohydrate and whey protein supplementation may help reduce the extent of, or enhance recovery from, muscle damage. This would not only benefit athletes during intense training phases, competition and during recovery from injury, but may also return people to the workplace earlier. Furthermore, improved functional recovery would also be of considerable benefit to a variety of populations, including those suffering from muscle wasting conditions, weakness associated with aging, neuromuscular disorders, acquired immunodeficiency syndrome, burn injury, cancer cachexia and prolonged sepsis.

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