The purpose of this lecture is to introduce how aquatic exercise is an attractive training method, especially for maintaining the cardiovascular fitness, during recovery from musculos-keletal injuries of the lower legs and/or from obesity. Though the energy expenditure of vertical movement in water is less than that on land due to the effect of buoyance, walking/running in water increases the energy metabolism largely enough to maintain the cardiovascular fitness level. In addition, water running on the spot with flotation device is capable of eliciting metabolic responses comparable to treadmill running on land. Therefore, comfortable and useful facilities for aquatic exercise should be constructed in each province for both healthy and injured persons to maintain and improve their cardiovascular fitness.

In order to investigate an effect of the excess fat of obese men on the respiratory-cardiovascular system, VO₂max was measured for seven obese, 16 ordinary and seven lean men. All subjects were university students, ages 18 to 25 years. Body composition was determined by densitometry. Furthermore, six non-obese young men participated in an added-weight experiment so as to estimate an effect of the excess fat of obesity. Results showed that there were no statistically significant differences in the absolute values of VO₂max, VEmax, and HRmax among the groups. Concerning the relative value of VO₂max to body weight, the obese group showed a significantly lower value of 40.4 ml/kg-min than the lean and ordinary group values of 51.5 and 48.8 ml/kg-min, respectively. However, no significant difference was found between the relative values of VO₂max per lean body mass of any of the groups. VO₂max for the obese group was 54.0 ml/kg-min, 56.0 for the lean group and 57.7 for the ordinary group. Such trends were very similar to the results of the added-weight experiment. Based on the values for the subjects in this study, this leads to the conclusion that the excess fat of obese men might act only as an inactive load and might not affect the ability of the respiratory-cardiovascular system. Besides, the threshold of obesity for men proposed by Behnke and Wilmore might be reasonable from the viewpoint of the absolute and the relative values of VO₂max.

Oxygen intake, pulmonary diffusing capacity (DL), pulmonary membrane diffusing capac ity (DM) and pulmonary capillary blood volume (Vc) were measured at rest and during maximal and submaximal work, with Filley's steady state technique on 3 athletes (middle distance runners) and 5 non-athletes. The results obtained in this study were as follows
(1) At rest, DL, DM, Vc in athletes were 28.3±3.7 ml/min/mmHg, 52.2±5.3 ml/min/ mmHg, 124.1±41.8 ml respectively, and in non-athletes were 25.6±1.0 ml/min/mmHg, 47.5±7.5 ml/min/mmHg, 114.7 ± 25.9m1 respectively.
(2) During submaximal works, DL, DM and Vc increased together with oxygen intake. At the same level of VO₂ athletes showed greater DL, DM and Vc than those of non-athletes. Contact time exponentially decreased as oxygen intake increased.
(3) At maximal work, athletes showed significantly greater max VO₂ DL, DM and Vc than those of non-athletes. But, contact time of athletes was not significantly greater than that of non-athletes.
(4) The results demonstrate that a higher DL, DM and Vc is accompanied by a higher aerobic capacity, a larger ventilatory capacity, and a larger cardiac output.

The present study was designed to investigate the effects of low altitude training on swimming performance with setting the same duration (3-wk) and the same level of altitude (2, 300m) . Eight male (Gm₁) swimmers aged 13 to 19 years and four male (Gm₂) and eight female (Gf₂) swimmers aged 13 to 18 years sent to Mexico City, and they conducted swimming work outs. All of them were top Japanese swimmers of various events. They repeated the swimming training twice a day continuously for four days with one day rest. Hemoglobin concentration (Hb), red blood cell count (RBC) and hematocrit (Hct) were determined before, during and after the altitude training several times. The values of Hb, RBC and Hct of all three groups increased significantly from before training to after training except Hb in Gm₁. On the other hand, these three variables did not necessarily increase during the altitude training. Gm₁ and Gf₂ tended to increase Hb and RBC during the training. As for swimming performance at sea level, the individual best swimming records were improved significantly in 200m events, but not in 100m events in Gm₁. Therefore, it may be concluded that 3-wk altitude (2, 300m) training possibly improve swimming performance in the events equal to or longer than 200m at sea level.

The explosive power output of both legs during extension movement was assessed in 271 male (aged 16-84 yr) and 248 female (aged 16-82 yr) subjects, and the table of evaluation for the value obtained was prepared with the function of sex and age. From a sitting position on a seat, leg extension movement was performed toward the foot plate in the forward, to which the body mass of each subject was applied as a resistance. The reliability of the power measurement was ascertained from the result that the coefficients of variation were under 5 x 10^-2 when the power output of 6 subjects was measured once a day for 10 days. On both sexes, the power output per body mass declined linearly with age. The regression equations between age (x) and the power output per body mass (y) were as follows.
male: y=-0.22 x+28.38 (r=.659, n=271; p<0.001)
female: y=-0.13 x+18.36 (r=.583, n=248; p<0.001)
For all groups classified by 10 years, the male indicated greater value than the female in corresponding groups. The ratio of the value for the female relative to that for the male was between 64.8% and 72, 0%. These results suggested that the power output for the male decreased at a higher rate, and the sex difference of it decreased as the age increased.

Near infrared spectroscopy has been used to determine the chemical composition of food stuffs, i, e., the protein, fat, and moisture content. Recently in the U. S. A, this technique was applied to the estimation of human body composition, and a portable instrument was developed. This study was designed to determine the prediction equation of body fat for Japanese people. 69 men and 52 women, aged 18 to 58 years, covering a wide range of percent fat levels, physiques, physical activity levels, had body fat estimated by hydrostatic weighing (HW), skinfold thicknesses (SF) and near infrared spectroscopy. Near infrared interactance spectra were measured on the anterior midline of the biceps halfway (between the anticubital fossa and acromion), the spectral data from which gave best correlation with HW and SF compared the other sites, using the wavelength of 947 nm. The spectral values and percent fat values obtained from HW about 1/2 of subjects were used to develop a prediction equation. This equation was then used to predict % body fat of the other 1/2 subjects. The correlation coefficient between % body fat as predicted by the near infrared method and as predicted by the HW technique was 0.88 (p<0.001, SEE=3.2) . This correlation value was similar to the value between % body fat as predicted by HW and as predicted by SF. In the American data, the correlation coefficients were higher when the other variables were added ; height, weight, age, but in the Japanese they did not almost change even when the other variables were added. There was not a difference between the spectra of right and left arm values. In the results, the prediction equation of % body fat for the Japanese population was determined as follows:
% body fat =54.14-29.47× (the spectral data at 947 nm) [r=0.88, p<0.001, SEE=3.2] (for right arm) .

Resting O₂ consumption following exercise at ventilatory threshold (VT) intensity was measured in order to investigate the magnitude and duration of excess post-exercise O₂ consumption in untrained men. Nine untrained males (mean age 24.8±1.5 years) exercised for one hour at VT intensity (58.2±1.7% of VO₂max) on a cycle ergometer, and then rested for 12 h sitting in a comfortable armchair (post-exercise) . On a separate day the subjects rested for 12 h but without preceding exercise (non-exercise) . O₂ uptake (VO₂) and heart rate (HR) were measured for 5 min every 30 min throughout the 12 h rest period and again at 24 h following the exercise. High-carbohydrate meals (carbohydrate 112.8±5.1 g, protein 9.7±0.4 g, fat 1.8±0.1 g) were given to the subjects at 2, 7 and 12 h following the exercise. The total energy intake per day was 1591.7±71.8 kcal. V0₂ and HR were significantly higher, and respiratory quotient (RQ) was significantly lower at most of the measured time-points for post-exercise than for non-exercise. Total energy consumption for the 12 h rest period was 957.3±25.5 kcal for post-exercise and 840.3±15.8 kcal for non-exercise, respectively. After 24 h no difference was observed in VO₂ and HR between post-exercise and non-exercise, but RQ was significantly lower in the former than in the latter (0.86±0.05 vs. 0.90±0.04, p<0.05) . These results suggest that exercise for one hour at VT intensity enhances resting VO₂ for at least 12 h, and elevates the rate of fat utilization for at least 24 h.

The metabolic rate, HR and thermal responses of 26 children, aged 7-8 years (6 boys, 7 girls) and aged 9-11 years (7 boys, 6 girls), were measured during head-out immersion in water. In the water bath, a bicycle ergometer was set and water temperature wes maintained at 26±1°C. Thirty minutes measurements of heat production (cal⋅min^-1⋅m^-2), HR, rectal (T_re) and skin (T_sk) temperatures were obtained under experimental conditions of resting and bicycling in water.
The rate of decrease in HR and T_re were significantly greater in the younger group than the older, irrespective of sex, in resting condition (P<0.001, P<0.01, respectively), but any differences could not be found in bicycling condition.
Heat conductanc (K) from body surface were calculated. In resting condition in water, older girl group showed K=94.1 (cal⋅m²⋅°C ⋅min^-1) and younger boy group K=142.2 and in bicycling condition in water they were 213.8 and 276.9, respectively.