The purposes of this study were to investigate the relationships between physical activity variables and physical fitness, and between amount and intensity of physical activity in children and adolescents. Subjects were divided into two groups : 178 children (99 boys aged 9.8±0.6 and 79 girls aged 9.7±0.6) who had not reached the age of peak height velocity (PHV), and 336 adolescents (141 boys aged 15.0±1.1 and 195 girls aged 15.3±1.2) who had reached the age of PHV. Physical activity level (PAL : total energy expenditure/basal metabolic rate) which indicates the amount of physical activity, and time engaged in each of physical activity intensity (light, moderate and vigorous), which indicates the intensity of physical activity were estimated from uni-axial accelerometer. Physical activity was monitored for 3 consecutives days : 2 weekday and 1 weekend day. Moreover, physical fitness test suggested by the Ministry of Education, Culture, Sports, Science and Technology was applied. Results of this study showed that PAL was closely related to physical fitness in children, while time engaged in vigorous activity was more related to physical fitness in adolescents. On the other hand, time engaged in light and moderate activity was closely associated with PAL in younger girls, whereas in younger boys, PAL was closely related to time engaged in moderate and vigorous activity. However, time engaged in moderate activity was more related to PAL in the adolescent group. These results suggest that the relationship between physical activity variables and physical fitness and between amount and intensity of physical activity might vary according to the growth development of boys and girls respectively.

The purpose of this study was to investigate the effects of different sitting postures, by change of seat height, on lower extremity muscle activation and maximum power during explosive bicycle pedaling exercises. The subjects performed 5 sec maximum pedaling exercises at three different seat heights.‘High’ seat height was defined as 95% of leg length, ‘Middle’ was 90% and‘Low’ was 85%.
The results were summarized as follows: A) At 3 revolutions, maximum power at‘High’ was significantly higher than that at‘low’. B) Pelvic angle at‘High’ was significantly higher than that at‘Low’. C) The maximum extension angle of the knee joint was a significantly high value in descend. ing order of‘High’, ‘Middle’ and‘Low’. D) mEMG of the Erector spinae and Biceps femoris at‘High’ was significantly higher than that at‘Low’. E) At‘High’, there was a significant correlation between maximum power of 3 revolutions and mEMG in the Gluteus maximus. In addition, maximum power at 3 revolutions tended to correlate with mEMG in the Biceps femoris and Vastus lateralis.
These results suggest that in explosive pedaling exercises, different sitting postures by change of seat height, have different influences on hip extension muscle activation and maximum power.

The present study examined the effect of the long-term intake of chicken breast extract (CBEX), which contains carnosine and anserine, on carnosine content in skeletal muscles of humans and on short-period exercise performance with high intensity.
Before and after CBEX was orally given to 13 healthy male subjects for 30 days, pieces of their muscle (M. vastus lateralis) were excised and carnosine concentration in the muscle was measured. Before and after the test period, the subjects exercise performance (mean and peak power body weight) was determined by pedaling for 30 sec. On the basis of baseline concentrations of carnosine, the subjects were classified into two groups: low (n=8) and high (n=5) carnosine-baseline groups. In the former group, intake of CBEX increased carnosine concentration in the muscle (p<0.05), resulting in significant correlation between increased rate of carnosine concentration and mean power. These results suggest that exercise performance depends on carnosine concentration in the muscle, and that taking carnosine-containing foods may improve exercise performance.

It is known that lactic anions and hydrogen ions (H⁺) produced during intense exercise are partly transported or diffused from muscle to blood resulting in the production of non-metabolic CO₂ through the bicarbonate buffering system. The purpose of the present study was to examine the reliability of the estimation of non-metabolic CO₂ output using respiratory gas analysis during incremental exercise. Six healthy subjects underwent an incremental pedaling exercise test accompanied by respiratory gas and arterial blood sampling. The rate of non-metabolic CO₂ output (VCO₂-NM) was calculated by subtracting projected metabolic VCO₂ from actual VCO₂ after CO₂ threshold (CT) . CT was determined using a modified V-Slope method. Bicarbonate (HCO₃^-), pH, CO₂ partial pressure and lactate concentration were measured from arterial blood samples using automatic analyzers. The kinetics of VCO₂-NM and HCO₂^- were compared throughout the exercise test. VCO₂-NM was significantly correlated with HCO₃^-decrease after CT (r=0.976, p<0.001) and the kinetics of VCO₂-NM and HCO₃^- decrease were similar during exercise. Furthermore, the amount of non-metabolic CO₂ output (NM-CO₂) calculated integrating VCO₂-NM above CT was significantly correlated with the difference in HCO₃^-between CT and exhaustion (r=0.929, p<0.01) and with the difference in arterial blood pH between rest and exhaustion (r=0.863, p<0.05) . However, NM-CO₂ was not significantly related to maximum ventilation (r=0.111, ns) . These results suggest that the estimation of non-metabolic CO₂ output during incremental exercise proposed in the present study is reliable. It was also suggested that the primary factor which influenced nonmetabolic CO₂ output during incremental exercise was the addition of H⁺ into blood and not hyperventilation.

The purpose of the present study was to determine the change in total excess volume of CO₂output (CO₂excess) due to bicarbonate buffering of lactic acid produced during exercise and change in swimming performance following resistance training for 8 weeks in competitive swimmers. Ten healthy university competitive swimmers were assigned to either a resistance training and swimming training group (COMBINE: N=5) or a swimming training only group (SWIM: N=5) . Muscle mass was measured using magnetic resonance imaging (MRI) . CO₂excess and blood lactate concentration were measured during incremental exercise on a cycle ergometer and swimming performance was measured during competition. COMBINE showed a significantly higher percentage change in muscle mass (11.1±4.5%) than SWIM (3.5±2.5%) . The percentage change in CO₂excess, CO₂excess per body weight (CO₂excess/BW) and CO₂excess/BW per blood lactate accumulation (CO₂excess/BW/ΔLa) during exercise was significantly higher in COMBINE (107.3±60.1, 102.6±56.8, 59.1±37.7%, respectively) than in SWIM (42.5±10.0, 42.9±10.4, 13.4±22.4%, respectively) . The percentage change in swimming performance was significantly higher in COMBINE (2.2±1.8%) than in SWIM (-2.0±3.6%) . A negative correlation between percentage change of muscle mass and percentage change of CO₂excess/BW/ ΔLa (SWIM: r=-0.993, P<0.01, COMBINE: r=-0.744, P>0.05) was found. It was suggested that combined swim and resistance training resulted in greater increases in the bicarbonate buffering system (CO₂excess/BW/ΔLa) . However, increases in muscle mass may have subsequently caused a relative decrease in the contribution of the bicarbonate buffering system.

The purpose of the present study was to investigate the relationships between the peak running velocity, and aerobic and anaerobic capacity in incremental running in pre- and post-competitive season using eight long distance runners. Measurements were peak running velocity, VO_2max, running velocity and VO₂ at respiratory exchange ratio (RER) 1.0, and blood lactate after exhaustion in the incremental running test. Correlation analysis revealed that pre-season velocity at RER 1.0 and post-season blood lactate were both related to peak running velocity. Furthermore, change in peak running velocity was related to change in blood lactate between pre-and post-season. These results suggest that factors that probably influenced running performance change from aerobic capacity in the pre-season to anaerobic capacity in the post-season, and that running performance during the competitive season may be highly dependent upon anaerobic capacity.

To obtain a viewpoint concerning evaluation of endurance type of athletes, we investigated the difference in physiological responses between middle- and long-distance runners in an incremental running test. Measurements were VO₂max and time of its appearance, change of VO₂ from 1.5 min before exhaustion to exhaustion (ΔVO₂), heart rate (HR), and blood lactate after exhaustion.
Results were as follows.
(1) The time of VO₂ max appearance in the middle distance runners was earlier than in the long distance runners.
(2) VO₂max was significantly higher in the long distance runners than in the middle distance runners.
(3) Blood lactate after exhaustion and HRmax were significantly higher in the middle distance runners than in the long distance runners.
(4) Blood lactate after exhaustion was significantly related to ΔVO₂ (r =-0.660, P<0.05) .
These findings suggest that the endurance type of athletes could be evaluated from the time of VO₂max appearance, blood lactate after exhaustion and HRmax in incremental running, and that VO₂max appearance may be effected by high blood lactate accumulation.

This study investigated the relationship of high-power work capacity with physiological variables during supramaximal intermittent exercise and individually measured alactic (ATP-CP), lactic (LA), and oxygen (O₂) energy delivery systems. Nineteen university handball players (experiment 1) and 23 university basketball players (experiment 2) performed an intermittent exercise routine consisting of a combination of high-power and low-power exercise. The exercise protocols were a laboratory test consisting of pedaling on a bicycle ergometer (experiment 1) and a field test consisting of a running protocol incorporating changes in direction (experiment 2) . The main results were as follows :
(1) The ATP-CP system was significantly related to power output during the early stage of intermittent exercise and the O₂ system was significantly related to power output in the middle and late stages of intermittent exercise. As an indicator of the O2 system, blood lactate concentration during submaximal exercise correlated more closely with power output during intermittent exercise compared with VO₂max/BW. The LA system was not significantly related to power output during intermittent exercise.
(2) Subjects were divided into 2 groups according to energy delivery ability and then power output ability during intermittent exercise was compared. The high ATP-CP system group had a significantly higher power output during the early stage of intermittent exercise compared with the low ATP-CP system group. The high O₂ system group had a significantly higher power output in the middle and late stages of intermittent exercise compared with the low O₂ system group. Compared to the low O₂ system group, the high O₂ system group had a higher absolute VO₂ during the low intensity active recovery periods of intermittent exercise, as well as a tendency to have lower blood lactate levels. The high LA system group showed lower power output over the course of intermittent exercise compared with the low LA system group.
These results indicate that the O₂ system is important for exerting higher power output during supramaximal intermittent exercise.

Bone (tibia, femur, and lumbar spine) and blood samples were obtained from 100 (50 males and 50 females) Wistar-Imamichi rats in groups aged 3, 5, 7, 9, 12, 15 and 20 weeks old to investigate the changes in bone mass during puberty in relation to insulin-like growth factor 1 (IGF-1), IGF binding protein (IGFBP) -3, osteocalcin (OC) and sex steroids in normal rats.
Sharp increases in BMD (bone mineral density) in the tibia, femur and lumbar appeared earlier in female than in male rats, and the BMD in females tended to be higher than in males between 5 and 9 weeks old. After 9 weeks old, BMD in males was higher than that in females, as BMD in males continued to increase whereas that in females tended to remain in a steady state after this stage. This sex-related difference in changes in BMD pattern is probably related to the serum concentrations of IGF-1, IGFBP-3, testosterone, and 17β-estradiol with maturation. In males, marked increases in serum IGF-1 and IGFBP-3 concentrations appeared earlier than that in serum testosterone level. IGF-1 and testosterone peaked at 9 weeks of age, and thereafter remarked in a steady state, whereas IGFBP-3 reached a peak at 7 weeks of age, and then declined gradually. In females, the changes in patterns of serum 17β-estradiol, IGF-1, and IGFBP-3 levels were very similar. The levels increased gradually from 3-5 weeks old, peaked at 9 weeks, and then decreased slowly thereafter. In contrast, serum OC concentrations remain relatively high from 3 to 9 and from 3 to 7 weeks old in males and females, respectively, although OC in both sexes declined gradually with aging.
These observations suggest that BMD development occurs earlier in female than in male rats. This sex-related difference in changes in the BMD pattern may result from the earlier onset of puberty in females, and from the sex-specific differences in concentrations of IGF-1, IGFBP-3 and sex steroids with maturation.

In this study, the difference between the effects of “power-up type” and “bulk-up type” strength training exercise was investigated by analyzing parameters such as structural and functional adaptations in the neuromuscular system. Eleven subjects were divided into power-up and bulk-up groups. The power-up group comprised five male subjects who performed 5 sets at 90% of one repetition maximum (1 RM) with a 3-min rest between sets (repetition method) . The bulk-up group comprised six male subjects who performed 9sets at 80-60-50%, 70-50-40%, and 60-50-40% of 1 RM with rest intervals between sets of either 30 s or 3 min (interval method) . Both groups performed isotonic knee extension exercise twice a week for 8 weeks. The power-up group showed a lower rate of improvement than the bulk-up group in terms of cross-sectional area (CSA) of the quadriceps femoris at levels 30%, 50% and 70% from the top of the femur, and also in average isokinetic strength (Isok. ave. ; 180 deg/s, 50 consecutive repetitions) . However, the power-up group showed a greater rate of improvement in 1 RM, maximal isometric strength (Isom. max), and maximal isokinetic strength (Isok. max ; 60, 180, 300 deg/s) . Furthermore, the rate of reduction in strength over 50 consecutive isokinetic repetitions decreased in the bulk-up group. On the other hand, the power-up group showed no significant changes in the above throughout the entire training program. These results indicate that the characteristics of the two types of training exercise are as follows : (1) power-up exercise is effective mainly for improving muscular strength and anaerobic power, and (2) bulk-up exercise is effective mainly for improving hypertrophy and anaerobic endurance. These findings support the idea that “power-up type” and “bulk-up type” strength training exercises should be applied appropriately according to the training aim.