Postexercise increase in nitric oxide in football players with muscle cramps

Nitric oxide, a free radical inter- and intracellular messenger molecule, i s important in exercise physiology. This study tested the hypothesis that s erum nitric oxide concentrations change after strenuous exercise with sever e generalized muscle cramps. The study group consisted of 77 professional f ootball players in preseason training. All players' concentrations of serum nitrite and of other serum chemicals were determined during their preseaso n evaluations and compared with the concentrations in 40 serum samples take n from 25 of those same players who required intravenous rehydration for se vere generalized muscle cramps after a training session. Player weight and percentage of body fat were significantly higher in players who received in travenous fluids than in players who did not. The serum of players requirin g intravenous hydration showed evidence of skeletal muscle breakdown (incre ases in lactate dehydrogenase, creatinine phosphokinase, aspartate aminotra nsferase, and alanine aminotransferase) and of dehydration (elevations in p rotein, blood urea nitrogen, and cholesterol), The major finding, however, was a nearly 300% increase in serum nitrite concentrations in players requi ring rehydration, There were no correlations between concentrations of nitr ate and of any of the other serum chemicals. These data support the hypothe sis that large amounts of nitric oxide are synthesized in professional foot ball players after strenuous exercise with severe muscle cramps. The study design did not allow us to determine whether this increase in nitric oxide was due to exercise or muscle cramps or both, but it does provide a basis f or evaluating these relationships.