Effect of single bouts of moderate and high intensity exercise and training on equine peripheral blood neutrophil function

The effects of single bouts of moderate (30 to 40 per cent VO(2)max) and hi gh (115 per cent VO(2)max) intensity exercise on equine peripheral blood le ucocyte function were evaluated by determining neutrophil phagocytosis and oxidative burst activity before and after treadmill exercise and training. Prior to all exercise tests, the possible effect of diurnal variation was e valuated in samples obtained from four resting horses. Subsequently eight h orses underwent moderate and high intensity exercise protocols and then com menced a 17-week training period. High intensity exercise tests were repeat ed in week 10, after 7 weeks of endurance training, and in week 17, after a further 6 weeks of high intensity training. Time of sampling had a signifi cant effect on neutrophil function for resting, untrained horses. Prior to training, moderate intensity exercise was associated with improved neutroph il phagocytosis and oxidative burst activity. High intensity exercise was a ssociated with transient impairment of these responses. A similar reduction was not demonstrable following high intensity exercise in weeks 10 or 17 o f training. Neutrophil function in week 17 was suppressed at all sampling t imes relative to results obtained in week 10, suggesting that high intensit y training may have been associated with a general reduction in neutrophil function. (C) 2000 Harcourt Publishers Ltd.