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.

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.

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.

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) .

To investigate the relationship between maximal aerobic power (VO₂max) and fatigu-abililty during repeated isokinetic contractions, 39 male speed skaters (mean 20.8 years) served as subjects. They were divided into two groups according to their VO₂max levels ; high VO₂max group (HI, n=19) and low VO₂max group (LO, n=20) . VO₂max was measured in all subjects during incremental exercise on a bicycle ergometer and body composition was determined by densitometry. Cross-sectional area (CSA) of the leg extensor muscles was evaluated using ultrasonic method. Fatiguability was assessed during the fatigue test consisting of 50 repeated isokinetic knee-extensions at an angular velocity of 180 deg⋅sec^-1. Remark-able findings include :
1. There were no significant differences in body composition and thigh composition between the two groups except for high subcutaneous fat in group LO.
2. There were significant differences in VO₂max between group HI (3.93l⋅min^-1, 67.3 ml⋅kg LBM^-1⋅min^-1) and group LO (3.59l⋅min^-1, 59.9 ml⋅kg LBM^-1⋅min^-1) .
3. In the fatigue test, the average initial values did not differ, however, the average final values were higher in group HI. Also, a significant difference was observed in per unit CSA between the two groups.
4. Higher peak forces (kg) in group HI were observed after the initial 30 dymanic contractions per unit CSA and % of peak values (% peak force) .
5. A close relationship was demonstrated between VO₂max per LBM and the fatigue index, i. e., the mean decline in peak force with 50 contractions (r=-0.37, p<0.05) .
Based on the present findings it is suggested that maximal aerobic power (VO₂max) influences the rate of fatigue development even during short-term maximal isokinetic contractions, and that there may be some physiological cross-linkages between cardiopulmonary regulation and the metabolic properties of skeletal muscles. This finding is also in conformity with earlier results indicating the importance of oxygen delivery as a limiting factor for muscle performance.

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 purpose of this study was to compare two methods of CO₂ rebreathing-equilibrium method (Collier, 1965) and extrapolation method (Defares, 1958) -for determining the mixed venous CO₂ pressure (PvCO₂) during exercise. Following a sitting rest for 5 min, five healthy males performed upright bicycle ergometer exercises with work rate of 100 and 150W for 5 min. During both at rest and in exercise, PvCO₂ was measured twice to evaluate the reproducibility of both methods. The equilibrium method was performed according to that by Jones & Campbell (1982) . In the extrapolation method, instead of using the graphical analysis described by Klauaen (1965), PvCO₂ was directly calculated by applying the modified exponential equation (Defares, 1958) . In the duplicate tests, coefficient of variation was lower while correlation coefficient was higher, with increasing work rate in both methods. It was noted that these tendencies were more pronounced in the extrapolation method than in the equilibrium method. It was concluded that in contrast to the results of Auchincloss et al. (1980), the extrapolation method was more reproducible than the equilibrium method.

Oxidation of lactate at rest (RE, n=4), or after short strenuous exercise (EX, n=6) was investigated in rats. Food and water were given ad libitum before experiment. In EX, rats ran to exhaustion at the speed of 80-100 m·min^-1. Immediately after exercise, 4 μCi of (U-¹⁴C) lactate was injected into aorta through an indwelling catheter. In RE, (U-¹⁴C) lactate was injected into the rats at rest. Expired gas was collected by a Brooks type bottomless chamber on treadmill belt for 120 min. In EX, exercise duration was 109±18 sec (mean±SE), and maximum blood lactate concentration after the exercise was 23.7±2.1 mM (mean±SE) . Cumulative percent recovery of ¹⁴C as ¹⁴CO₂ for 120 min was 48.5±2.8% for EX and 61.7±0.9% for RE (mean±SE) . Significant difference was found between these two rates (p<0.01) . After 50 min of recovery, mean volume of ¹⁴CO₂ expired per min in RE was significantly greater than that in EX (p<0.01) . Mean volume of ¹⁴CO₂ expired per min per VCO₂ in RE was always greater than that in EX, and significant difference was found at 7.5 min of recovery (p<0.01) . It is concluded that although the rate of recovery of ¹⁴C as ¹⁴CO₂ after exercise is lower than that at rest, the major pathway of lactate metabolism after short strenuous exercise is oxidation.

In 31 asthmatic children, we investigated the change of the structure on the time of living, an amount of exercise by pedmeter and measured pulmonary ventilatory function during 28 weeks swimming training.
The result showed 58.07% of contribution factor to the structure on the time of living on children with asthma and dynamic play time after school were significantly shorter in asthmatic than non-asthmatic children (p<0.05) . After 28 weeks, we could not find any significantly differences of dynamic play time between asthmatic and nonasthmatic children.
An amount of exercise in daily life from the point of view of walking step number by pedmeter were significantly less in aged 6-9 years boys and girls, and aged 10-12 years boys than non-asthmatic children (respectively, p<0.05, p<0.01) . However, after 28 weeks, we could not find any differences between asthmatic and non-asthmatic children.
Forced vital capacity (FVC) and rate of forced expiratory volume on one second (% FEV_1.0) were increased after 28 weeks than the begining of swimming, and we found the strength of their breathing muscles.
On according to perform the great swimming distances (averages 220m in boys, 325m in girls), all asthmatic children became very lively and actively.