In eight groups of healthy male athlets, aged 19-44 years, serum urea, alpha-amino nitrogen and free tyrosine were determined before and after physical exercise of different duration. Exercise was competitional running, skiing, march or bicycle ergometer work, its duration between 15 and 765 min. The results were compared with previous data from this laboratory and those of other authors. After about 60-70 min of exertion, there is a significant fall in serum amino nitrogen and a rise in urea and free tyrosine; the magnitude of these changes correlated well to the duration of exercise. Likewise, there is a significant correlation between increase in serum urea and decrease in amino nitrogen. The observed changes strongly suggest an increased breakdown of nitrogen-containing compounds during prolonged exercise.

Thirty young male adults matched in two experimental groups (n = 12) and a control group (n = 6) were investigated before and after an 8-week strength training period. Group A trained with few repetitions and maximal loads, whereas group B had more repetitions with smaller loads. Both groups lifted the same total load during each training period, four times a week. Maximal voluntary strength (MVS) of a shot-put arm movement, muscular excitability and contractile properties (time to peak of contraction with threshold stimuli, half relaxation time) were measured in M. deltoideus and M. triceps brachii, C. longum, for two durations of stimulation. Increases of 14.8% (group A) and 12.2% (group B) in MVS were observed. Muscle excitability significantly increased in all types of training and both muscles. Significant shortening of the contraction time, dependent on the type of training, was observed in both studied muscles. It appears that the strength training in group A involved the fast fibers of both muscles, whereas in group B the training influence was less marked, and affected both fast and slow fiber types.

Eleven male subjects took part in a 100 km running competition. Alterations in the total plasma protein and in ten individual plasma protein concentrations in blood and urine were measured prior to the run, immediately after and after 1 day of recovery. Five individual proteins showed a 7-10%, and lysozyme a 40%, increase in the plasma after the run. On the contrary, the haptoglobin concentration fell to 40% of its pre-race level. None of these variations were correlated with the plasma volume change. The present data showed a moderate hemolysis, as evidenced by plasma lysozyme and hemoglobin-haptoglobin binding. The urinary excretion of plasma proteins was slightly increased, especially albumin and alpha1-acid-glycoprotein. The renal clearance of plasma proteins revealed that the 100 km run induced a moderate increase of glomerular permeability without any signficant change in the tubular reabsorption process.

Sixteen young adults were investigated before, immediately after and 24 h after swimming 5,200 +/- 618 m in 90 min. Mean pulse rate at the end of exercise was 151.3 min-1; skin and rectal temperature both slightly increased. Except for a marked leukocytosis, no changes were observed in other blood parameters (hematocrit, hemoglobin, erythrocytes). Serum enzyme activities showed (except for triosephosphate dehydrogenase) marked increases which in the case of creatine kinase and of malate dehydrogenase did not return to preexercise level on the next day. No hypoglycemia occurred in any of the subjects. Blood lactate increased to 4.2 mmol/l at the 15th min of exercise and at the end was still slightly above the resting value. Free fatty acids, free glycerol, 3-hydroxybutyrate, serum urea and uric acid rose markedly after swimming, whereas alpha-amino nitrogen, triglycerides, and serum magnesium significantly decreased. The electrical excitability of the two investigated muscles (M. vastus med. quadr. and M. deltoides) showed opposite changes, which was ascribed to their different involvement during swimming.

In 18 groups of trained healthy male subjects (n = 166; age 17--42 years) the influence of type and duration of long-lasting exercise on the changes of creatine kinase (CPK) and hexose phosphate isomerase (PHI) activity in serum was studied. Above 65--70% of maximal aerobic capacity, a serum enzyme activity increase proportional to the exercise time was found with a different slope in each of the three exercise types examined [a) bicycle ergometer; b) ski race; c) impact-type exertion]. Work duration of more than 300 min induced in the third type of exertion an accelerated increase in serum CPK. A third degree equation best describes the changes in serum CPK for nine of our groups and five others from the literature. To ascertain the possible influence of intravascular hemolysis, sera were mixed with autologous erythrocyte hemolysates and enzyme activity measured. The findings are discussed with reference to critical aspects of the analytical methods, possible causes of serum enzyme changes, and possible use of enzyme measurements in evaluating adaptation of the organism to prolonged exercise.