Exercise sessions (swimming in rats and treadmill running in humans) resulted in stimulation of neutrophil degranulation in the experiments with animals and in the human study. Myeloperoxidase (MPO) (+67%) and lysozyme (+51%) quantities in the plasma of rats increased significantly immediately after exercise. The blood plasma lysozyme concentration was increased by 41% at the 6th min of treadmill exercise in athletes. The blood concentrations of neutrophil proteins normalized both in humans and animals at rest. The neutrophil protein concentrations in blood increased in parallel with the decrease of their level in leukocytes. The neutrophil capacity for an oxidative burst was not changed by the exercise, but decreased for 3-6 h in the post-exercise period. Such dynamics of the oxidative burst activity suggest a lack of association between this parameter and the degranulation process. The neutrophil proteins that appear in blood during degranulation can be involved in enhancing the bactericidal potency of blood, the activation of granulopoiesis, neutrophil efflux from bone marrow, and the conditioning of blood endothelium for leukocyte extravasation.

The primary purpose of this study was to examine the effects of high-intensity acute exercise on neutrophil infiltration in different muscle fiber types of untrained rats and to compare postexercise neutrophil accumulation in muscles of untrained and trained animals. The effect of high-intensity acute exercise on blood neutrophil degranulation reaction in trained animals was also elucidated. Neutrophil enzyme myeloperoxidase (MPO) was determined as a measure of neutrophil migration into muscles and blood neutrophil degranulation. Male albino rats were subjected to acute exercise and 5 weeks of training. The used model of intensive acute exercise consisted of 5, 15, and 25 intermittent swimming bouts with the addition of weight (8% of total body mass) for 1-min each, followed by 1.5-min rest intervals. MPO was analyzed in quadriceps muscle (white and red portion) and in soleus muscle 24 h after acute exercise. MPO content in resting blood plasma and neutrophils was determined 48-h following the completion of a training process. In addition, MPO content in the trained rats was measured immediately (in blood plasma and neutrophils) after and 24 h (in muscles) following a single-bout of exercise to exhaustion. The remaining two-third of the trained animals were exposed to a single-bout of nonstop swimming with the addition of 6% body mass until exhaustion. These animals were sacrificed immediately and 24 h after loaded swimming to analyze leukocyte count, MPO content in blood plasma and neutrophils and in muscles, respectively. About 24 h after exercise MPO concentrations in the red portion of quadriceps muscle and in soleus muscle were 4-7-fold higher as compared to the white portion of m. quadriceps. There was an association between the quantity of repetitive bouts of swimming and MPO content in the muscles. The duration of swimming to exhaustion of trained rats was 3.8-fold longer than untrained sedentary control. At rest, plasma MPO concentration was found to be 40% higher in trained rats compared to untrained controls (P < 0.05). Postexercise plasma MPO concentrations were significantly higher both in untrained (+137%; P < 0.05) and trained (+81%; P < 0.05) rats compared to resting values. At rest neutrophil MPO concentration was found to be 33% lower in trained rats compared to untrained controls (P < 0.05). There were no significant differences in muscle MPO concentrations between untrained and trained rats at rest. A single-bout of exercise to exhaustion produced a greater increase in MPO content in untrained compared to trained rats. The data suggest that postexercise neutrophil infiltration is more intensive in red fibers types compared to white fiber types. A smaller neutrophil infiltration in muscles of trained animals after exhaustive exercise suggests a protective effect of previous training to muscle injury.

The accuracy of regulating exercise intensity by Ratings of Perceived Exertion (RPE) was examined. Subjects underwent 4 production trials, 2 on a treadmill (P1A, P1B) and 2 on a cycle ergometer (P2A, P2B). 9 untrained subjects used only their perceptions of effort to regulate exercise intensity. Target intensity was the RPE equivalent to 60% VO2max. Exercise intensity (VO2) during P1A, P1B, and P2A did not differ from the target, but during P2B was lower than target. During P1A and P1B heart rate did not differ from the target but was lower than target during P2A and P2B. RPE seems a valid means of regulating exercise intensity during repeated bouts of treadmill exercise at 60% VO2max; however, exercise intensity during repeated bouts on the cycle ergometer may be lower than target.

The data suggest that 7 d of exercise is sufficient not only to improve insulin sensitivity and fat oxidation but also to favorably alter adipokine secretion, independent of changes in body weight or composition.