A study on climatic conditions, body temperature and cardiovascular response during outdoor exercise in physical education class in the schoolboys of Chulalongkorn University Demonstration Elementary School

Abstract

This descriptive study aimed to determine climatic conditions, body temperature, cardiovascular responses, hydration status and the incidence of heat illness during outdoor exercise in physical education class in 457 schoolboys of Chulalongkorn University Demonstration Elementary School. The study was performed in the first (July-September) and second (November-February) semesters of the academic year 2009. Body weight, blood pressure, pulse rate and core body temperature were measured before and after outdoor exercise in physical education class. Physical education classes climatic conditions were measured every five minutes and video image of the events were recorded for evaluation of exercise duration and intensity as well as the incidence of heat illness. However, the subjects were allowed to drink water and urinate during their physical education classes. It was found that the characteristics of the schoolboys were as follows: age 8.38 ± 1.56 years, height 130.72 ± 10.45 cm, weight 30.81 ± 9.39 kg, BMI 17.68 ± 3.35 kg/sq.m and BSA 1.05 ± 0.19 sq.m. The climatic conditions included the ambient temperature 33.56 ± 2.55℃, relative humidity 54.15 ± 8.12% and Wet Bulb Globe Temperature (WBGT) 28.87 ± 2.35℃ (first semester 29.95 ± 1.87℃, second semester 28.32 ± 2.39℃). Total duration of physical education class was 31.97 ± 11.10 min. Outdoor physical activity consisted of skill practice (duration 24.11 ± 11.04 min, intensity < 3 MET) and sport playing (duration 11.48 ± 5.53 min, intensity 2.5-9 MET). Before and after outdoor exercise, the percent change in systolic and diastolic blood pressure, mean arterial pressure and pulse rate was increased by 16.00, 21.59, 19.05 and 22.05%, respectively. Sweat rate was 391.16 ± 186.75 mL/hr. Core temperature was increased by 0.66 ± 0.41℃ from 36.48 ± 0.37℃ to 37.14 ± 0.42℃. There were 20 schoolboys (7 schoolboys in first semester, 13 schoolboys in second semester) whose core temperature reached up to 38℃; this accounts for 4.38% of all subjects. Among these, 18 schoolboys did not drink water and 2 schoolboys drank water of 158 and 340 mL while exercising in physical education class. However, no incidence of heat illness was found. In conclusion, there is a tendency for heat illness during outdoor activities in physical education class in primary school children. It is recommended that climatic conditions and children’s core temperature be measured before the start of physical education class. The children should be encouraged to drink enough water before and during exercise