Substrate utilization during 60 min of endurance exercise (50-60%VO2max) performed in the morning and evening was compared in 11 subjects. After rising at 0600-0630 with a 10-h fast, they exercised without a meal (fasting) or after intake of 40g of carbohydrate feeding (snack) . In addition, subjects consumed curry and rice for lunch 4-h before exercise and exercised at about 1630 (evening) . In the fasting trial, there was no significant change in plasma glucose (J 100.8 vs 93.0; R 101.0 vs 105.6 mg/dl) before and after exercise between the joggers (J) and the runners (R) . However, plasma glucose in only one subject, who had no night meal, decreased to less than 70 mg/dl. Also, although the plasma free fatty acid level was elevated by more than 50% in both groups, the highest value observed was 0.86 mmol/l. Therefore it was suggested that no subjects developed hypoglycemia and weakness that plasma free fatty acid was not markedly elevated during 60 min of endurance exercise after the fasting trial, whereas there was a tendency for plasma β-hydroxybutyrate to be increased in the joggers compared with the runners. The availability of blood-borne substrates in the trial evening was characterized by a two-fold elevation (p<0.01) of the insulin level prior to exercise, a 10% decline in plasma glucose and suppression of the normal increase in plasma glycerol and FFA turnover during exercise compared with the other two trials, whereas the results for the fasting and snack trials were similar. The total energy expenditure for 60 min of exercise in the snack trial was significantly 4-5 % higher than in the fasting and evening trial (mean ± SE= 654.4 ± 26.7 kcal, 619.2 ± 21.2 kcal and 627.5 ± 27.5 kcal, respectively) . Percentage of energy obtained from lipid was determined based on the respiratory quotient, which was similar (48.6 vs 49.7%) between the fasting and snack trials. This, however, differed significantly (p<0.01) from the percentage of lipid metabolized (32.6%) during the evening trial. These data indicate that fasting and snack trials in the morning result in preferential oxidation of fat during endurance exercise.
A study was conducted to analyze the height growth velocity curve based upon the maturity rate. Ninety-eight longitudinal data points for height (for subjects aged 6 to 17 years) were obtained retrospectively from health examination records in 1983. Growth distance and growth velocity curves of each individual were described by the wavelet interpolation method, and PHV age was determined with the described graph using computer simulation. We classified the growth velocity curve by the maturity rate approximated according to the PHV age. As a result, it was shown that the after-growth spurt in early maturity and somewhat early maturity type appeared more than in the average and somewhat late maturity types, and that conversely, the mid-growth spurt in the late maturity and somewhat late maturity types appeared more than in the early maturity and somewhat early maturity types. Specifically, it was demonstrated that two mid-growth spurts appeared in the late maturity and somewhat late maturity types.
The effects of different training programs on the force-velocity relation and the maximum power output from the elbow flexor muscles were examined in eighteen male adults. The subjects were divided into three equal groups (G 30, G 30+0, G 30+ 100) . Training for G 30 was performed with ten repetitions at 30% Po (Po: maximum strength), for G30+0 with five repetitions at 30% Po and five contractions with no load (0 % Po), and for G 30+100 with five repetitions at 30% Po and five isometric contractions (100% Po) . Maximum power was increased significantly in all groups after training. The amounts of power increase tended to be greatest for G 30+ 100, followed by G 30+0 and G 30. A significant difference was observed between G 30 + 100 and G 30 + 0. Maximum strength increased most in G 30 + 100, followed by G30 and G 30+0. The strength gain in G 30+100 was significantly greater than that in G 30. Maximum velocity increased significantly in all groups. No significant difference in velocity gain was observed between any pair of groups. These results suggest that isometric training at maximum strength (100% Po) appears to be a more effective form of supplementary training to increase power production than would no load training at maximum velocity.
To clarify changes in body temperature during endurance exercise in patients with spinal cord injury (SCI), we measured tympanic temperature (Tty) and skin temperature in the head, arm, chest, thigh, shin and calf in 5 patients with SCI (T6-T 12) and 7 normal controls during 30 minutes arm cranking exercise (20 watts) from 10 minutes before the initiation of exercise until 10 minutes after the termination of exercise in an artificial climate room at a temperature of about 25°C with a relative humidity of about 50%. The Tty in the SCI group was lower than that in the control group from 10 minutes before the initiation of exercise to 10 minutes after the termination of exercise with a significant difference only at the initiation of exercise. The difference in Tty slightly decreased with continuation of exercise. The Tty in the SCI group at rest was 36.05-37.15°C. Four patients in this group showed a decrease of 0.04-0.12°C in the early stage and an increase of 0.66°C±0.19 (mean±SD) at the end of exercise over the value at the initiation of exercise. The skin temperature was lower in the SCI group than in the control group in all sites excluding the arm. Significant differences were observed in the head in the early stage of exercise and after exercise, in the chest from 10 minutes before the initiation of exercise to 5 minutes after the termination of exercise, in the thigh from 10 minutes before the initiation of exercise to 10 minutes after the termination of exercise, in the shin 10 minutes and 5 minutes before the initiation of exercise, and in the calf from before to 15 minutes after the initiation of exercise. In the SCI group, marked individual differences were observed in the skin temperatures in the thigh, shin, and calf, suggesting specificity of the skin temperature response in and near the paralysis area. Results in Tty in this study suggested no heat retention in the SCI patients. Therefore, the risk for heat disorders seems to be low during moderate or mild exercise under moderate temperature environment at a temperature of about 25°C with a relative humidity of about 50% even when the skin temperature is low, and thermolysis is not marked.
In order to examine muscle activities, surface electromyo-grams (EMGs) were recorded from the triceps surae muscles (lateral gastrocnemius: LG, medial gastrocnemius: MG, soleus: SOL) during prolonged isometric contractions at 20°of ankle joint angle under constant load (10% MVC) . The results were summarized as follows; 1) EMG recordings were obtained which showed complementary activity in each muscle in the time course. Changes in activity was found between whole muscles in the synergist of triceps surae muscles. 2) Muscle activity most frequently took the form of MG+SOL, followed by MG acting alone and SOL acting alone. Ta/Ts value (the ratio of total activity period and total silent period on EMG activity) showed 4.0 in MG and SOL. In contrast, it showed 0.3 in the LG. 3) In the latter half of all exercise times, frequent changes in activity were shown, and Ta/Ts value increased in the gastrocnemius muscle and decreased in the soleus muscle. These results indicate that frequent changes in activity in the latter half were caused by the reduc tion in Ts in the gastrocnemius muscle, and the reduction in Ta in the soleus muscle. 4) Mean integrated EMGs increased significantly in the middle and latter phases in each burst activity, but those in the latter phase did not increase compared to those in the middle phase. These results suggest that the rotation of activity between muscles may have occured before the remarkable increase of EMG activity with fatigue.
The purpose of this study is to find a key to clarifying the mechanism of lactic acid production during exercise. Five healthy men performed the grip and wrist flexion exercises at different occasions. Exercise intensities were increased by 5% MVC (maximum voluntary contraction force) per minute from 10% MVC. Intracellular pH, oxygenated hemoglobin/myoglobin (Oxy-Hb/Mb), inorganic phosphate (Pi), and phosphocreatin (PCr) in forearm flexor muscles were measured by 31P-MRS and NIRS. The lowest Oxy-Hb/Mb concentrations during the grip and wrist flexion exercises were 40.7± 8.86% (average±SE) and 15.4 ± 2.26%, respectively. These results suggest that oxygen remain sufficient in the muscles at least during the grip exercise. Intracellular pH dropped as exercise intensity rose above 25% MVC for the grip and above 10% MVC for the wrist flexion exercise. These results support the idea that oxygen deficiency is not the only cause for lactic acid production during exercise. On the other hand, intracellular pH fell with either negative or positive relations to Pi/PCr ratio, Pi, and PCr in each exercise. These results support the suggestion that the main causes of lactic acid production during exercise are the changes in ADP, Pi, and PCr.