Relation between changes in serum hypoxanthine levels by exercise and daily physical activity in the elderly.

Effect of exercise at mild intensity on the serum levels of hypoxanthine was studied in eleven healthy elderly subjects. They were divided into the active and sedentary groups according to their daily physical activity. They performed exercise testing to walk for 5 minutes keeping heart rate at approximately 70% of the maximum heart rate. Mean intensity of exercise estimated according to Karvonen's formula in the active or sedentary group was 41.8 +/- 9.6% or 34.1 +/- 6.1%, respectively. In the sedentary group, the serum hypoxanthine levels at 10 minutes after completion of walk load was significantly higher than that before exercise. Changes in the serum hypoxanthine levels in the active and sedentary groups were -0.97 +/- 1.36 and 0.80 +/- 0.57 micromol/liter, respectively (p < 0.05). This result suggests that mild intensity exercise increases the serum hypoxanthine concentration in the elderly leading inactive daily life, and physical activity suppresses an increase in the serum hypoxanthine levels by mild exercise.