Abstract

Objectives: While moderate exercise can benefit one's health, acute and vigorous exercise may have the opposite effect. Strenuous exercise can induce alterations in the physiology and viability of circulating leukocytes, which have a causal relationship with exercise-induced immune distress. In the present study, we investigated the use of the mitochondria transmembrane potential (MTP), a noval functional parameter of the energized and viable status of leukocytes, for monitoring the immuno-modulating effects of short-term, high-intensity exercise.

Methods: Twelve healthy volunteers with a mean VO2max of 70.4 ml/kg/min underwent 3 consecutive days of high-intensity exercise (85% of the VO2max for 30 minutes every day). Blood samples were collected at multiple time points immediately before and after each exercise session and at 24 hour and 72 hours after the completion of the exercise. The Leukocyte MTP and apoptosis and circulatory inflammation markers were measured by flow cytometry and enzyme-linked immunosorbent assays.

Results: The MTP of the peripheral blood leukoctyes declined immediately following the first exercise session and remained subnormal 24 hours later. The MTP did not normalize until 72 hours post-exercise. The sequential changes in the MTP were consistent among the three leukocyte subpopulations (polymorphonuclear cells (PMN), lymphocytes and monocytes) and were statistically significant (p < 0.05). The leukocytes displayed a gradual and incremental change in their propensity for apoptosis during and after the exercise period. Similarly, the plasma concentrations of the TNF-αand FasL were elevated during the exercise sessions and did not normalize by 72 hours following the completion of the exercise. The correlation between the change in the leukocyte MTP and plasma concentration of the TNF-αand FasL was variable, but significant for the PMN and lymphocytes (p < 0.05).

Conclusions: Short-term high-intensity exercise can lead to a significant and prolonged dysfunction in the mitochondrial energized status of the peripheral blood leukocytes, which will be accompanied by an increased propensity for apoptosis and elevated pro-inflammatory mediators. Our results lend support to the immunosupressive effects of excessive exercise and suggest that the MTP is a useful marker for those effects.