The effect of exercise on electrolytes and cortisol levels in serum and saliva was examined in 27 young, healthy male volunteers who performed graded submaximal cycle exercise for nine min at up to 85% of their age-predicted maximal heart rate. Seventeen men performed the Wingate anaerobic test for 30 s. A significant increase in pulse rate and systolic blood pressure and a decrease in diastolic blood pressure were found, and serum concentrations of Na+, K+, and lactate were significantly elevated immediately after exercise. A nonsignificant increase in saliva and serum cortisol levels was found. Significantly lowered salivary flow rate and elevated salivary K+, protein, and lactate concentrations were found within ten min after exercise. Salivary Mg2+ was significantly elevated after anaerobic exercise only.
The various ECG changes found in a group of 3,000 healthy athletes are discussed on the basis of eight representative ECG recordings. The common findings were sinus bradycardia, atrioventricular conduction disturbances, left and right ventricular hypertrophy according to the accepted voltage criteria, right axis deviation, intraventricular conduction disturbances (mainly in the right side of the heart), and various disturbances of the repolarization phase. The literature on this subject is reviewed, and the possible mechanisms involved in production of the various ECG changes are discussed. It is pointed out that in the absence of other evidence suggestive of cardiovascular disease, these changes should be considered as a normal variant and not lead to restriction of physical activity.
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