The purpose of the present study was to elucidate whether oxygen consumption of the respiratory muscles might influence the oxygen supply to the working muscles.
Oxygen consumption of the respiratory muscles and pulmonary resistance were measured in 10 male long distance runners (trained) and 10 sedentary male students (untrained) during bicycle exercise at three submaximal work loads. Oxygen con-sumption of the respiratory muscles was measured by increasing pulmonary ventilation with inhalation of 2% CO₂ in air. Pulmonary resistance was measured with the airway interruption method.
Pulmonary resistance was similar for the trained and untrained subjects. While, oxygen consumption of the respiratory muscles of trained subjects during exercise was, when compared at equal pulmonary ventilation of equal work load (kgm/min or %Vo₂ max), smaller than untrained (p<0.05) .
From the present study it was concluded that the respiratory movements of trained subjects were more efficient than untrained, and that oxygen consumption of the re-spiratory muscles affected the aerobic work capacity more in untrained subjects than in trained.

We studied the relationship between bone mineral density (BMD) and history of habitual exercise in a group of university students comprising 41 athletes (27 males and 14 females) and 39 non-athletes (24 males and 15 females), ranging in age from 18 to 28 years. Their athletic history during elementray, junior and senior high schools was surveyed. Subjects who had engaged in athletic activities more than 3 days/week for more than two years at each school level were classified as a former physically active group, whereas the others were classified as controls. The BMD of the femur (femoral neck, Ward's triangle, trochanteric region) and vertebrae (L2-4) was ieasured using dual-photon absorptiometry with a ¹⁵³Gd source. The following results were obtained: 1) University athletes showed significantly higher BMD of the femur and L2-4 than non-athletes. 2) No significant difference was found for either sex between the physically active group on elementary school days and the control group with regard to BMD of the femur and L2-4. 3) The BMD of the femoral neck and trochanteric region in the male physically active group on junior high school days was significantly higher than that in the control group. The BMD of the femoral neck in the female physically active group on junior high school days was significantly higher than that in the control group. 4) The BMD of the femur and L2-4 in the female physically active group on senior high school days was significantly higher than that in the control group, whereas no difference was found between these two groups for males. These results suggest that regular exercise during puberty is effective for increasing BMD, especially in females. The finding that increased BMD in association with physical activity on senior high school days was observed only in females may be due to the synergistic effect of estrogen and exercise.

Bone mineral content (BMC), fat weight (FAT) and lean tissue weight (LTW) were determined by dual-energy X-ray absorptiometry (DEXA) in 20 young adults of both sexes who were performing habitual exercise. From these data, body weight, lean body weight (LBW) and the percentage of BMC relative to LBW (BMC%LBW) were obtained. First, body density based on a two-component model (D₂) was calculated using the values of FAT and LBW of the subjects and the fat and lean densities of the Reference Body, Then percentage body fat (%Fat₂) was calculated using the formula of Brozek et al. The body density for a three-component model (D₃) was then determined from the values of FAT, BMC and LTW of the subjects, and the fat, bone mineral and lean tissue densities of the Reference Body. Percentage body fat (%Fat₃) was also calculated in the same manner as %Fat₂. Analysis of the data indicated that (1) females had higher values of BMC%LBW than males, and that (2) subjects whose %Fat₂ exceeded %Fat₃ by more than 1% were exclusively females whose BMC%LBW values were more than 6.1%. In contrast, those whose %Fat₂ was lower than %Fat₃ by less than -1% were exclusively males who had BMC%LBW values less than 5.2%. It is concluded that male subjects develop their muscles more than their bones with habitual exercise, which results in a lower BMC%LBW value than in females, and that for those with BMC%LBW values exceeding 6.1% (females) or less than 5.2% (males), %Fat calculation from body density using the formula of Brozek et a1. will produce an error of more than 1% if BMC%LBW is not considered.

The purpose of this study was to compare blood lactate concentration, lactate threshold (LT) and onset of blood lactate accumulation (OBLA) during an incremental bicycle exercise under a hot dry environment with those during the same workload under a thermoneutral environment. Eight unacclimated men performed an incremental test to exhaustion on a cycle ergometer during which the work rate was increased by 30 W every three minutes under thermoneutral (25°C) and hot dry (40°C) environmental conditions. Oxygen consumption (VO₂) -pulmonary ventilation (VE), gas exchange measures and earlobe blood samples for lactate analysis were obtained every minute during the test. LT (p<0.05) and OBLA (p<0.01) occurred at significantly lower VO₂ under the hot environment than those under the thermoneutral environment. Additionally blood lactate concentration was significantly higher (p<0.05) at each measurement period under the hot environment compared with that under the ther-moneutral environment. The correlation between LT and ventilatory threshold (VT) was not statistically significant under the thermoneutral (r=0.20) and hot dry (r=0.60) environments, These findings demonstrate that the hot dry environment may increase blood lactate concentration more and causes a leftward shift of LT and OBLA. Since blood lactate accumulation during incremental exercise is not considered to be the only factor which mediates VE, VT does not always accurately predict LT.

Boys and girls of elementary school (1 st, 3 rd and 6 th-grades), junior high school (2 nd-grade) and senior high school (2 nd-grade) were tested for 2 days to examine the reliability of grip strength, back strength, arm strength and leg strength.
The following results were obtained:
1. When elementary school boys performed three trials of these four items, over half boys recorded maximal value up to the second trial.
2. The reliability of tests applied to the left and right sides (grip strength, arm strength and leg strength) was not different each other.
3. In boys and girls attending elementary, junior- and senior high schools the reliability of grip strength was highest and the next was back strength.
4. Grip strength had statistically significant relationship to the other three items. Thus grip strength is considered to be the representative of four strength tests for growing boys and girls.

The types of skeletal single muscle fibers were studied with the distribution of myosin light chains (MLC) and tropomyosin (TM) to make clear the biochemical property and the possibility of the transformation of fiber types by physical training. Since soleus (SOL) muscle is widely used as an example of slow-twich muscle and extensor digitorum longus (EDL) muscle is used as one of fast-twitch muscle, single muscle fibers were prepared from SOL and EDL muscles of 5-6 weeks old male mice (strain DDY) . Total myofibrillar proteins of the muscle bundles or single muscle fibers were homogenized and fractionated with the micro two-dimensional isoelectric focusing/sodium dodecyl sulfate polyacrylamide gel electrophoresis (IEF/SDS-PAGE) . The fractionated proteins were visualized with coomassie brilliant blue stain method or highly sensitive silver stain method.
We found that there were at least two types of fibers in SOL and EDL muscles. In SOL muscle, one contained only slow form of MLC and the other contained both of fast and slow forms of MLC. In EDL muscle, one contained only fast form of MLC and the other contained both of fast and slow forms of MLC. The fiber containing only one form of MLC was classified into typical slow or fast fiber, and the fiber containing both forms of fast and slow types MLC was classified into intermediate fiber. Both of a form and β form of TM were invariably observed in all fibers of SOL and EDL muscles. Relative ratio of a form of TM to β form of TM was, however, larger in the typical fast fiber containing only the fast form of MLC than others. The ratio was smallest in the typical slow fiber. These results suggest the possibility of the continuous transformation in the phenotype of muscular proteins within a single muscle fiber by physical training.

This study was undertaken to examine whether carbohydrate loading gives a good effect to improve the endurance performance in Japanese subjects who had habitually eaten carbohydrate-rich diets. The glycogen content of the vastus lateralis muscle was determined in 6 healthy male subjects with the aid of the needle biopsy technique by setting different diets after glycogen store was depleted by exhaustive exercise.
Glycogen content of the vastus lateralis muscle after mix, low and high carbohydrate diets was 22.7±2.0, 11.6±1.6 and 36.6±4.5 g/wet muscle⋅kg (mean±SD), respectively, while exhaustive time was 75′39″±10′02″, 67′58″±14′11″and 92′10″±22′10″ (mean±SD), respectively. Thus, a good correlation was noted between muscle glycogen content and work time.
It was therefore concluded that the glycogen content of the working muscle was a determinant factor for the capacity to perform long-term heavy exercise and that carbohy-drate loading attained with low carbohydrate diet and exhaustive exercise followed by high carbohydrate diet had a good effect to perform heavy exercise even in Japanese who lived on carbohydrate-rich diet.

Energy expenditure during sport activities has been determined traditionally by the Douglas Bag Method and the Motion Time Study. However, those two methods do not yield accurate values when used in long continuous and/or vigorous physical activities. This study, therefore, measured oxygen uptake by means of a portable device “Oxylog”, and determined the energy expenditure of many sport activities. The experiments were carried out with 13 untrained male subjects (UTS), and 30 trained male subjects (TS) . The 30 trained men consited of ten tennis players, ten badminton players and ten basketball players. UTS played one set of doubles (tennis), one set of singles (badminton), two sets of singles (table tennis), two games (bowling) and jogged 10 minutes, But TS played only their major sports : one set of doubles (tennis), one set of singles (badminton) and two 20-minute halves (basketball) . The results were 0.172±0.017kcal⋅kg^-1⋅min^-1 for jogging (UTS), 0.146±0.028kcal⋅kg^-1⋅min^-1 for badminton (TS), 0.133±0.021kcal⋅kg^-1⋅min^-1 for basketball (TS), 0.130±0.018kcal⋅kg^-1⋅min^-1 for badminton (UTS), 0.102±0.016kcal⋅kg^-1⋅min^-1 for tennis (TS), 0.096±0.014kcal⋅kg^-1⋅min^-1 for tennis (UTS), 0.089±0.019kcal⋅kg^-1⋅min^-1 for table tennis (UTS), and 0.055±0.009kcal⋅kg^-1⋅min^-1 for bowling (UTS) . In comparison with UTS, TS exhibited higher values in tennis and badminton. This is considered to result from TS's better training. This result indicates that energy expenditure in playing sports activities depends on the level of player's ability. The method employed in of this study is believed to be the best choice at present. Many other sport activities must be reexamined in detail using this method.

The most characteristic feature of the triathlon is integration of the three endurance activities including of swimming, cycling and running, into a continuous task. So, it is necessary to identify the cardiorespiratory responses during the triathlon to develop a beneficial training program. Twelve male triathletes conducted a simulated triathlon test in a laboratory. This test consisted of continuous swimming, cycling and running using a flumepool, a bicycle ergometer and a treadmill, respectively. The exercise intensity and duration were 60% of maximal oxygen uptake during swimming, cycling and running for 30, 75 and 45 min, respectively. The results demonstrated that the residual effects of the prior exercise stage were observed during the latter exercise stage : The prior swimming stage produced an increment of oxygen uptake and heart rate during the cycling stage ; Prior swimming and cycling stages increased oxygen uptake, minute ventilation, heart rate and ventilatory equivalent to those during the running stage. These results suggest that the residual effects of the preceding exercise decreased the mechanical and respiratory efficiency by increasing the physiological demands of conducting the subsequent exercise. Therefore, triathletes are recommended to train themselves in a continuous task rather than separately.