Although it has been established that exercise is useful for health promotion, physical exercise may induce oxidative stress in humans. Our previous study showed that the concentration of plasma protein-bound sulfhydryl groups (p-SHs) was significantly decreased after strenuous exercise, i. e. full-marathon running and participation in an athletic training camp. Reactive oxygen species may cause oxidation of plasma proteins in vitro. To study whether moderate exercise for health promotion, e. g. jogging or walking, induces oxidative stress in human circulating blood, the authors examined the change in plasma p-SHs concentration following ergometric exercise at moderate intensity and of relatively short duration {Exercise 1: 80% ventilatory threshold (VT), 100% VT, and 110% VT; 30 min, Exercise 2 : 90% VT; 120 min} in 8 (23-28 yr; Exercise 1) and 6 males (23-28 yr; Exercise 2) respectively. The plasma p-SHs concentration did not changed significantly after Exercise 1 or 2. The data indicated that the exercise did not cause significant modification of plasma proteins, suggesting that it did not induce significant oxidative stress in the circulating blood.

The primary aim of this study was to examine moderate-to-vigorous physical activity (MVPA) levels in preschool children during indoor and outdoor free playing time and during preschool physical education (PE) classes. The secondary aim was to determine which types of PE lessons are the best for increasing the percentage of MVPA. Physical activity during free playing time and in lessons was objectively evaluated with a triaxial accelerometer in preschool boys and girls (n = 281). Minutes of physical activity were categorized into physical activity ratios (PAR). MVPA was defined as PAR ≥3.0. Time tables and PE lesson types were recorded using logs kept by class teachers. The percentage of MVPA in outdoor free playing time (38.9±16.3%) was significantly higher than that of indoor free playing time (12.6±10.1%, p<0.001). On the other hand, there was no significant difference between the percentage in MVPA in outdoor free playing time and the percentage in PE lessons (n=94: 38.0±19.4%vs. 34.9±15.8%, ns). After adjustment for gender, age, body height and weight and preschool, there were not significantly different the percentage of MVPA among contents of PE lessons. In conclusion, children engaged in almost 30~40% MVPA during outdoor free playing time or PE. The children also engaged MVPA during indoor free playing time.