Neutrophil function Stress hormone Cytokine Cortisol Interleukin-6 Oxidative stress
The depression of immune cell function that is typically observed after prolonged
exercise is thought to be largely mediated by increased plasma concentrations of
stress hormones and cytokines and possibly oxidative stress. The aims of this thesis
were to determine the effects of acute and longer term oral antioxidant
supplementation on immunoendocrine responses following prolonged exercise.
In study 1 (Chapter 3) it was shown that vitamin C ingested acutely before and during
prolonged exercise has little or no effect on immunoendocrine responses.
Furthermore, the combined ingestion of vitamin C with carbohydrate provides no
additional effects compared with carbohydrate alone. However, when vitamin C was
supplemented acutely, 2 h prior to, and during prolonged exercise in addition to on the
night before (14 h prior) exercise this limited the fall in neutrophil oxidative burst
activity (study 2, Chapter 4). This was probably a result of reduced direct oxidative
damage to neutrophils with vitamin C supplementation since there were no effects on
the cortisol, interleukin-6, leukocytosis or neutrophilia responses. Longer periods of
antioxidant supplementation (2 - 4 weeks) may be effective at blunting the cortisol,
leukocytosis and neutrophilia responses to prolonged exercise (Chapters 5 and 6) but
this had no effect on in vitro measures of neutrophil function. In study 5 (Chapter 7) it
was shown that acute pre-exercise dark chocolate (which contains polyphenols)
ingestion has some effects on plasma oxidative stress markers and circulating insulin
and glucose responses but not the immunoendocrine responses to prolonged exercise.
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.