One hundred and thirty-nine boys (6-14 years of age) were studied to determine the relationship between cardiac functions and body size during growth. Heart volume (HV) was obtained by X-ray method. Left ventricle diastolic and systolic demensions were measured by ultra-sound cardiography. Cardiac functions during growth were developed greatly, While cardiac functions as well as body size showed great deviations at equal age group. The individual differences became larger as the subjects grew. Although growth of cardiac functions were not always proportional to growth of body size the correlation between cardiac functions and body size at 10 to 13 years of age were significant (r=0.39-0.88, p<0.001). Increase in stroke volume (SV) and decrease in heart rate (HR) during growth were attributable to increase in end-diastolic volume (EDV) rather than smaller increase in end-systolic volume (ESV). HV, Ieft ventricle volume, cardiac muscle wall thickness, SV, and cardiac output (CO) were correlated significantly (r=0.42-0.78, p<0.001) each other. Heart volume to body surface area (BSA) ratio increased during growth, while cardiac index (CO/BSA) showed steady values.
The purpose of this study was to compare the aerobic capacity during swimming and running from the view point of maximal oxygen uptake (VO2max) and anaerobic threshold (AnT). Fifteen subjects (9 swimmers and 6 field athletes) performed progressive exercises until exhaustion by use of a treadmill and an experimental swimming pool. Respiratory responses were measurered using a computerized breath-by-breath test system for the determination of AnT and VO2max, and the time points where they occurred. The results were as follows ; (1) Between the two exercises, there were significant differences in fractional concentrations of end-tidal O2 (FETO2), CO2 (FETCO2) and pulmonary ventilation (VE) at the two time points. (2) On the interaction of two exercises and two exercise groups, there were significant differences in FETO2 and FETCO2 at the two time points, and in oxygen uptake (VO2) and VO2/wt at the AnT.
According to the prediction method of local muscle energy metabolic rate (Yokoyama, 1980), energy metabolic rates of the seven muscle groups were predicted with simultaneous measurements of total energy metabolic rate and bipolar surface EMG during four resting and four working postures. The subjects were 21 Japanese male volunteers aged 22.5±2.7 years. Four resting postures were relaxed standing, sitting on a chair, supine and prone postures. The present working postures were consisted of standing on tiptoes, half rising with knee extension (at 180°), half rising with knees bending at 120° and deep forward bending postures. The seven muscle groups were the muscles of the anterior abdominal wall (M1), the erector spinae muscles (M2), the muscles of the buttock (M3), the posterior femoral (M4), the anterior femoral (M5), the posterior crural (M6), and the anterior crural muscle group (M7). During standing on tiptoes M6 had the greatest metabolic rate (mean=21.94kcal/h) among the seven muscle groups, which was also greater than those of M6 during the other seven postures. During half rising at 180° it was pointed out through t-test (Student-test) that M2 and M4 demanded the greater metabolic rates, of which the mean values (n=21) were 29.51 and 6. 87kcal/h respectively. M5 required 45.78kcal/h during half rising at 120°, which was the greatest mean value in the present study. During deep forward bending posture the greater mean metabolic rates were 11.88kcal/h in M3 and 10.45kcal/h in M4. On the other hand, during relaxed standing the metabolic rates were 5.13 in M1, 7.94 in M2, 4.88 in M3, 2.37 in M4, 5.49 in M5, 9.61 in M6 and 0.57kcal/h in M7. Since each of the seven muscle groups was near to the minimum metabolic rate during the above four working postures, it was considered that relaxed standing has been adopted to the resting posture in standing. The metabolic rates of the seven muscle groups during sitting on a chair were less than those during relaxed standing. Especially it was shown that the metabolic rates of M4 and M6 reduced with the significant level p <0.001 and that those of M2 and M3 reduced with the significant level p < 0.01. During supine and prone postures the mean energy metabolic rates of the seven muscle groups were the least among the present tested postures, therefore it was interpreted to be reasonable that these postures has been adopted the sleeping postures in human daily life.