Nutritional aspects of exercise-induced fatigue

Abstract

University of Technology, Loughborough, Leics. LEI I 3 TUFatigue during exercise is a common experience irrespective of the level of activity and it is manifest as a decrease in exercise tolerance. This decreased exercise tolerance is most dramatically illustrated during various athletic competitions. For example, the runner who completes a marathon race is not only moving much more slowly than earlier in the race, but also crosses the finishing line with only the minimum of physical coordination. The onset of fatigue is even more dramatically illustrated by sprinters who as they fatigue towards the end of their race make their fellow athletes, who are also slowing down but less rapidly, appear to accelerate past them towards the finishing line. In sports which require skills of coordination, such as tennis, cricket or football, as fatigue develops so skill disappears and thus, what to the unfatigued spectators is still an 'easy shot, move, pass or catch' is not recognized as such by the participant. Fatigue is then readily recognized and experienced at the whole-body level. However, the physiological explanations for fatigue are not so readily available because of the complexity of the phenomena. In this presentation therefore, the metabolic aspects of fatigue in skeletal muscles during exercise will be the focus of attention rather than, for example, the contributions to fatigue, from interactions within the central nervous system. Apart from exercise which demands maximum exertion over a few seconds, fatigue may be regarded as having metabolic origins in the sense that it may be simply described as a mismatching of the rates of ATP utilization and resynthesis in skeletal muscles. This imbalance between the rates of demand and supply of ATP is redressed by decreasing the demand for ATP, i.e. by slowing down, which has various levels of acceptability depending on the urgency with which the activity has to be completed. Exercise intensityDuring exercise which can be sustained for a prolonged period of time, such as walking or slow running, the energy needs of the working muscles are covered by aerobic metabolism. The energy expenditure can be estimated from a determination of the person's oxygen uptake (vo,).

Effects of a multi-nutrient supplement on exercise performance and hormonal responses to resistance exercise

“…GH concentrations were elevated compared to PL values at Mid, Post, and +15. Ingestion of amino acids such as arginine have been show to acutely increase circulating levels of GH (Chromiak and Antonio 2002;Paddon-Jones et al 2004;Williams 1985). However, GH responses to resistance exercise are also highly dependent on the acute exercise program variables (such as load, intensity, and volume) (Godfrey et al 2003;Kraemer et al 1990).…”

“…In particular, L-arginine has been show to positively inXuence muscular strength and power with training (Campbell et al 2006). The mechanisms by which L-arginine may aVect athletic performance have yet to be elucidated; however, it might be via changes in GH and testosterone, both of which impinge upon transcription and translation processes, triggering enhanced muscle protein synthesis (Chromiak and Antonio 2002;Williams 1985).…”

The Effect of Treatment with Recombinant Human Erythropoietin on the Histological Appearance and Glycogen Content of Skeletal Muscle in Patients with Chronic Renal Failure Treated by Regular Hospital Haemodialysis

“…Previous studies have reported reduced muscle gly cogen stores in patients with acute renal failure and normal glycogen in patients with chronic uraemia [18]. However a poor nutritional state results in muscle glycogen depletion [19], and other muscle biopsy studies in patients with uraemia have reported evidence of chronic malnutrition [20,21]. Following treatment with rhEPO there was an increase in muscle glycogen content to within the normal range in all patients.…”

“…Muscle strength is a function of 92 Davenport/King/Ironside/Will/Davison The Effect of Erythropoietin Treatment on Uremic Sceletal Muscle both the number of muscle fibres present within a muscle and the diameter size [32], In this study there was an increase in muscle fibre diameter following rhEPO therapy. Typi cally the increase in type I fibre size would be expected to correlate with an improvement in exercise capacity as dem onstrated by bicycle ergometry or treadmill testing [33,34], which has been reported by others [19,23,24], Increased muscle glycogen content would be expected to increase both brief maximal exercise [35] such as sprint performance [25] and to increase endurance fitness [23], due to the in creased glycogen stores in the type II fibres. Hence these changes alone would be expected to increase exercise per formance.…”

Dietary requirements and athletic performance of horses

“…Within the limits of aerobic respiration, oxygen consumption is proportional to both energy metabolism and velocity on level ground in human athletes (Williams 1985). On the other hand.…”