Effects of Exercise Intensity, Duration and Recovery on in vitro Neutrophil Function in Male Athletes

The aim of the present study was to compare the effects of exercise at 80 %VO₂max (resulting in fatigue within 1 h) with more prolonged exercise at a lower work rate (55 % VO₂max for up to 3 h) on blood neutrophil function and plasma concentrations of Cortisol, glutamine and glucose. Eighteen: healthy male subjects (mean±SD age 22.5±3.7yrs, VO₂max 60.1±6.6 ml·kg^-1·min^-1) cycled on an electrically braked ergometer at 80 % VO₂max to fatigue (37±19 min). On another occaision, separated by at least one week, subjects performed excercise on the same ergometer at 55 % VO₂max for 3 h or to fatigiue, whichever was the sooner. Mean exercise time was 164±23 rmin. The order of the trials was randomised. Both exercise bouts caused significant (p < 0.05) elevations of the blood leucocyte count and plasma Cortisol concentration and reductions in the in vitro neutrophil degranulation response to bacterial lipopolysaccharide and oxidative burst activity. After exercise at the lower work rate for a longer duration, plasma Cortisol concentratiotn was higher, blood leucocyte and neutrophil counts were highier, blood lymphocytes, plasma glucose and indices of neutrophil function were lower than those observed at 80 % VO₂max. Plasma glutamine only fell significantly during recovery after (the more prolonged exercise. We conclude that when exercise is very prolonged, the diminution of innate immune function is greater, or at least as great as that observed after fatiguing exercise at higher work rates. Furthermore, reductions in neutrophil function after exercise at 80 % VO₂max were not related to changes in the plasma glutamine concentration, although both plasma glutamine and neutrophil function were decreased at 1 and 2.5 h post-exercise in the long duration exercise trial.

Key words

Exercise - neutrophils - glutamine - Cortisol - immune