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INTRODUCTION

Consistency in training is a common trait of successful athletes. An athlete who is injured or ill may be required to reduce training load or withdraw from training and competition. With insufficient training stimulus, detraining can occur, which involves a partial to complete loss of the metabolic and physiological adaptations to training. The rate of loss depends on the athlete’s stage of training, the degree of training load reduction, and the timeframe over which this interruption occurs. While therapeutic interventions such as medication in combination with various physical modalities are key considerations in injury management, nutrition also plays an important role.

Training-induced immunosuppression has been reported in some athletes. The immune system may be compromised during periods of high-intensity training or when there is insufficient food intake, thereby increasing susceptibility for opportunistic infection and slowing the rate of recovery. All macronutrients and several micronutrients are involved in immune function.

This chapter focuses predominantly on nutritional considerations that help to minimise the adverse implications of a potentially suppressed immune system associated with repeated high-intensity exercise; prevent short-term infective illnesses common in athletes (e.g. upper respiratory tract infection (URTI), gastrointestinal tract (GIT) infection, skin infection); and assist athletes recover from injury. Chapter 21 considers GIT conditions and diseases in more detail, including the treatment of gastrointestinal symptoms associated with exercise.

THE IMMUNE SYSTEM: ROLE IN INFECTION AND INJURY

The physiological stress of high-intensity exercise can compromise immune function and increase susceptibility to infection. Athletes travel frequently to competition and because they are in close proximity to other people, the risk of exposure to opportunistic infection is high. Illness and injuries are an unfortunate consequence of sports participation. An effective treatment and management plan for athletes recovering from infection and injury requires a thorough understanding of immune system processes and their link with various nutritional interventions and nutrient biomarkers.

The immune system comprises physical, cellular and soluble components that work together to defend against pathogens and repair tissue damaged by injury or illness. The physical components of the immune system include the skin, epithelial cells, cilia and mucosal fluids. The cellular components include white blood cells (leucocytes) that are subdivided into lymphocytes, monocytes and granulocytes (neutrophils). A number of endogenous proteins, including immunoglobulins, complement, lactoferrin and lysozyme, form the soluble components of the immune system. Pathogenic agents include viruses, bacteria, fungi, allergens and toxins. Body tissues and cells can be damaged by trauma, cuts, burns and surgery, and in the context of exercise and sport, from the effects of an infection, or acute or chronic injury. An immune and inflammatory response typically involves a coordinated process of cellular and soluble components that work synergistically to destroy and remove infected or damaged cells. In some individuals, regulation of the immune response is compromised, leading to an autoimmune disorder such as type 1 diabetes or rheumatoid arthritis, where the ...

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