Effects of short- and long-term exercise on urinary cGMP excretion in healthy subjects and in patients with coronary artery disease.

The possibility that systemic formation of cyclic guanosine monophosphate (cGMP) could reflect the level of cardiovascular fitness was investigated. The relations between physical activity and systemic formation of cGMP were evaluated in healthy volunteers and in patients with coronary artery disease (CAD). No significant differences were observed in the basal urinary excretion of cGMP in highly trained runners, sedentary subjects, and in patients with CAD, despite the large differences in aerobic exercise training between groups. In addition, the basal levels of cGMP in CAD patients failed to increase after a 12-week cardiac rehabilitation program. Short-term exercise, on the other hand, was associated with significant increases in urinary cGMP excretion. A 42-km marathon increased urinary cGMP excretion by 272%. The 15-km race increased urinary cGMP excretion by 330%. In CAD patients, 30 min of supervised exercise on a treadmill, at 80% of patient's maximal heart rate, induced a 60% increase in urinary cGMP, which returned to preexercise levels 90 min after termination of the exercise. Completion of the 12-week cardiac rehabilitation program improved exercise capacity and the magnitude of increase in cGMP levels induced by short-term treadmill exercise. Our findings suggest that cGMP increases during and shortly after short-term exercise and that the magnitude of the increase seems dependent on the intensity of the exercise and on physical fitness. Exercise training in healthy subjects and in CAD patients enhanced the amount of cGMP produced during short-term exercise, which might be responsible for some of the protective cardiovascular actions of exercise. The short half-life of cGMP may explain why the basal resting levels of cGMP are not appropriate predictors of a subject's physical fitness.

Urinary excretion of nitric oxide metabolites in runners, sedentary individuals and patients with coronary artery disease: effects of 42 km marathon, 15 km race and a cardiac rehabilitation program.

BACKGROUND: The mechanisms by which regular exercise is associated with decreases in all-cause and cardiovascular mortality are unknown. Nitric oxide (NO) may have a role, as it is known to be an important factor in cardiovascular regulation. The relationships between physical activity and systemic formation of NO were evaluated in healthy volunteers and in patients with coronary artery disease (CAD). METHODS: Urinary excretion of NO metabolites (nitrates + nitrites) was measured in 50 men. Group 1 comprised 14 highly trained runners (90 km/week) who were tested before and after a marathon race of 42.2 km. Group 2 comprised 11 well trained men (64 km/week) who were tested before and after a 15 km race. Group 3 comprised 12 sedentary individuals who gave a single urine sample. Group 4 comprised 13 patients with CAD who were tested before and after a 6 km walk. RESULTS: Group 1 showed the highest basal levels of urinary NO metabolites: 10.10 mmol/g creatinine; they were followed by group 2, with 5.60 mmol/g creatinine, group 3 with 1.59 mmol/g creatinine and patients with CAD (group 4), who had 0.35 mmol/g creatinine. After the marathon, those in group 1 showed a significant (P=0.0001) reduction of 80% in the excretion of NO metabolites. The 15 km race (group 2 and the 6 km walk (group 4), produced nonsignificant reductions in NO excretion. Patients with CAD were prospectively evaluated before and after a 12-week cardiac rehabilitation program. Their urinary excretion of NO metabolites (mmol/g creatinine) at the end of the program was 157% higher than at baseline (P=0.034). A positive, significant correlation (P=0.006) was observed between the increases in exercise capacity [in METs (one MET is equal to the body's oxygen consumption at rest, and corresponds to 3.5 ml/Kg/min)] and in NO metabolite excretion induced by the 12-week program. CONCLUSIONS: The baseline urinary excretion of NO metabolites increases with increasing levels of physical activity (chronic aerobic exercise). Patients with CAD had lowest levels of urinary NO metabolites and these increased in direct proportion with the gain in functional capacity. These findings suggest that increased NO production may be a major adaptive mechanism by which chronic aerobic exercise training benefits the cardiovascular system. The marked increase in NO production induced by long-term, high levels of aerobic exercise may be protective in athletes undertaking strenuous levels of exercise.

[Exercise and nutrition]. / Ejercicio y nutrición.

Aerobic exercise, particularly that of long duration and/or intensity, requires careful consideration of dietary aspects. The most important energy source are carbohydrates, and they must provide the majority of daily calories. Adequate hydration before and during exercise is the key to avoid hyperthermia. The consumption of glucose solutions during exercise is debatable, and electrolyte preparations are of no proven value, except in extreme circumstances.