We studied the effects of 8 weeks of endurance training on the metabolism in rats. Different treadmill speeds, which corresponded to 2 mM and 4 mM blood lactate concentrations, were used to vary the intensity of the endurance training. After 8 weeks of training, blood lactate concentrations had decreased whereas β-hydroxyacyl-CoA dehydrogenase activity had increased. Citrate synthase activity in the m.extensor digitorum longus (EDL), and m.tibialis anterior (TA) of rats trained at the 4 mM level was higher than in rats trained at the 2 mM level and in control rats. In addition, muscle glycogen content in the hindlimb was higher and muscle TG content in the m.soleus (SOL) was lower in trained rats. These results suggest that training at 4 mM level significantly increases muscle mitochondrial oxidative capacity, and fatty acids are utilized as an energy source regardless of exercise intensity at least in the 2 to 4 mM intensity range. We concludes that an intensity of 4 mM is a useful level with which to elucidate the various adaptations to endurance training.

Five long-distance runners and five non-athletes were examined on lipoprotein metabolism at rest, during, and after pedaling exercise (60% of the maximal oxygen uptake) . At rest, the concentrations of the cholesterol (Cho.), triglyceride (TG), and phospholipid (PL) of very low density lipoprotein (VLDL) were kept at low level in the longdistance group compared with the non-athletes. The difference is significant (p<0.01) . On the other hand, the levels of the Cho, and PL of high density lipoprotein (HDL) were maintained high (p<0.05) . The concentrations of the TG of VLDL are in negative correlation with those of the Cho. (p<0.01) and PL (p<0.001) of HDL at rest. A positive correlation between Cho. and PL of HDL was also noted (p<0.001) . The TG of the VLDL decreased gradually with pedaling exercise in the long-distance group, reaching about 12 percent below the resting value just after exercise. However, no apparent change was noted in the non-athletes.
The results obtained indicate that the long-distance runners, compared with nonathletes, tends to use lipids in order to produce energy for exercise. There is little possibility of transferring from the Cho. and PL of VLDL to the lipoprotein during exercise for the results of no change in concentrations of the Cho. and PL of low density lipoprotein (LDL) and HDL. We concluded that the Cho, and PL of VLDL could gradually transfer to HDL by a heap of the endurance exercise for long period.

A study was conducted to examine the efficacy of indicators of anaerobic work capacity or estimations of anaerobic energy expenditure by measuring Δ blood lactate and O₂ debt after short-term maximal exercise. Eight male subjects performed cycle ergometer pedaling against 5.5-7.0 kp resistance with maximal effort for 45 s. After pedaling, venous blood samples were drawn serially at 1 min intervals from 1 to 10 min, for measurement of peak blood lactate. Anaerobic energy expenditure was determined in terms of both alactacid and lactacid energy expenditure, on the basis of Δ blood lactate (L-method) and O2 uptake kinetics (D-method) during recovery.
The following results were obtained:
1) The correlation coefficient between lactate and performance was higher (about 0.3-0.5) when lactate was expressed as the estimated value of lactate production rather than Δ blood lactate. A significant relationship (r=0.740, p<0.05) was found between lactate production and peak power.
2) When O₂ uptake after recovery for 60 min did not recover to the baseline of O₂ uptake at rest, O₂ debt was calculated using a baseline of O₂ uptake just before the end of recovery. This O₂ debt was significantly correlated with work at any time of recovery.
3) There was a significant relationship between lactate production and lactic O₂ debt, which was significantly correlated with work.
4) When lactacid energy was calculated using a formula of 1.7×Δ blood lactate and 0.3 kcal/g lactate, there was no significant difference between anaerobic energy expenditure calculated by the L- and D-methods for up to 30 min during recovery.
It was concluded that a) the estimated value of lactate production and O₂ debt calculated using a baseline of O₂ uptake just before the end of recovery could be employed as an indicator of anaerobic work capacity, and b) Δ La multiplied by a coefficient of 1.7 and 0.3 kcal/g lactate was more appropriate for estimating anaerobic expenditure in short-term maximal cycle ergometer pedaling.

The effects of 6 weeks (5 days/week) of endurance training under hyperoxia (60% O₂ plus 40% N₂) on carbohydrate and fat metabolism were studied in 42 male rats. The rats were divided into four groups ; normoxia control (NC, n=8), hyperoxia control (HC, n=9), normoxia training (NT, n=12), and hyperoxia training (HT, n=13) . NT and HT groups were made to run on a treadmill in a metabolic chamber at a speed of 20 m/min for 30 min. The metabolic chamber was perfused with hyperoxic gas. VCO₂ values at rest (HC) and during exercise (HT) under hyperoxia were significantly lower (p<0.01) than VCO₂ values at rest (NC) and during exercise (NT) under normoxia, respectively. These results appear to indicate that a decreased respiratory exchange ratio was induced by hyperoxia. The results showed that at 15 min after the last training there were no differences between NT and HT in the glycogen or triglyceride content of the liver, heart, m, gastrocnemius, and m. soleus. However, blood glucose at 15 min in NT (109±13 mg/dl) was significantly lower (p<0.05) than the corresponding value at 15 min in HT (133±11 mg/dl) and at 48 h after the last training in NT (149±7 mg/dl) . The glycogen content of the liver in HC (36.4±2.6 mg/g wet wt) was significantly higher (p<0.05) than the corresponding value in NC (26.1±1.9 mg/g wet wt) . In the HT group, the triglyceride content of the liver at 48 h was lower (p<0.01) than the corresponding value at 15 min. However, the triglyceride content of the heart at 48 h in HT was significantly higher (p<0.05) than the value at 15 min. Basal lipolysis in HC was significantly higher than the corresponding values in NC, NT and HT, but there were no differences among the groups in norepinephrine-induced lipolysis. These results indicate that endurance training under hyperoxia might alter the content of tissue glycogen and triglyceride as a result of decreased carbohydrate consumption and increased fat utilization during fasting and/or exercise.

The series of ECG examination were performed to study the influence of different kinds of exercise on heart of two untrained middle aged healthy male volunteers.
One of them was assigned to run 10 kilometers or so, as fast as he could, once a day for 17 days. The other was assigned to run on a treadmill of three degree gradient for 20 minutes with a speed of 150 meters per minute once a day for 10 years. This volume of exercise was designed at a workload requiring 2/3 of his VO₂max value.
In the former case, frequent supraventricular premature beats with ventricular aberrant conduction occurred on the 21 st day from the beginning of the study. These changes on ECG were complicated with sinus arrhythmia and complete AV block on the 23 rd day. Sinus bradycardia and supraventricular bigeminy with ventricular aberrant conduction were noted on the 44 th day. Supraventricular bigeminies still persisted on the 213 th day, however they disappeared after that.
The latter developed interpolated ventricular premature beats at rest for the first time in the 5 th year from the beginning of the study. These premature beats disappeared during exercise and recurred at rest. In the 8 th year ventricular premature beats became to show bigeminies.
These results suggest that the severe exercise could cause various types of arrhythmia for a long period of time after the cessation of exercise even if the term of exercise would be short. On the other hand, the moderate load of exercise could not cause clinically significant arrhythmias inspite of continuous performance for a long term.

A study was performed to investigate the effect of ingestion of two different carbohydrates immediately after exhaustive exercise on muscle glycogen restoration in rats. The carbohydrate solu-tions used were 20% maltodextrin (osmolality: 270 mOsm/kg⋅H₂O) and 20% glucose (osmolality: 1370mOsm/kg·H₂O) . At both 30 and 60 min after oral ingestion, the osmolality in the gastric residue was significantly higher in the group given the glucose solution than in the group given the maltodextrin solution. The concentration of serum glucose at both 30 and 60 min after oral ingestion was significantly higher in the group given maltodextrin than in the group given glucose. Compared to the group given glucose, the group given maltodextrin had significantly higher muscle glycogen contents in M. plantaris and M. gastrocnemius at both 30 and 60 min after oral ingestion. Furthermore, the muscle glycogen contents in the group given maltodextrin returned to the levels in resting control rats 60 min after oral ingestion. Thus it is concluded that ingestion of maltodextrin solution immediately after exhaustive exercise might be effective for rapid restoration of muscle glycogen.