A study was conducted to investigate the effect of endurance exercise on plasma lipid peroxidation product and on the activity of scavenging enzymes in erythrocytes in short and long distance runners. The activity of scavenging enzymes [superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) ] in erythrocytes, plasma lipid peroxide level (malondialdehyde, MDA) and the activity of plasma lactate dehydrogenase (LDH) and creative phosphokinase (CPK) were measured in resting condition. The subjects then exercised on a bicycle ergometer at 70% of maximum heart rate for 60 min. SOD, GSH-Px and CAT activities were significantly decreased by 34%, 23% and 20% (p<0.001) respectively in sedentary subjects after endurance exercise. However, SOD and GSH-Px activities were not significantly changed in both short and long distance runners except a slight reduction in CAT activity was detected after endurance exercise. These results demonstrate that training in short and long distance runners increases the activity of the main free radical scavenging enzymes in erythrocytes and that the endurance exercise inactivates CAT only. Moreover, plasma lipid peroxide level and the activities of LDH and CPK were significantly increased in sedentary subjected after endurance exercise when compared with those in short and long distance runners. It is concluded that there is a degree of adaptation to training in short and long distance runners that might be effective in muscle damage protection after endurance exercise.

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To clarify the relationship between cardiac myosin isozyme composition in running-trained rats and the sympathetic nervous system, we examined whether the sympathetic nervous system could contribute to the modulation of cardiac myosin isozyme in running-trained rats, using atenolol, a selective blocker of cardiac β₁ adrenegic receptor. Male Wistar strain rats (4 weeks old) were used, and divided into four groups: control sedentary (CS), control trained (CT), atenolol sedentary (AS), and atenolol trained (AT) . The AS and AT groups were treated with atenolol in drinking water (65 mg/kg/day) for 9 weeks. The CT and AT groups were trained by treadmill running (at 30 m/min for 1 h/day, 5 days/week), starting at 7 weeks old, for 6 weeks. At 13 weeks old, the hearts were excised. The left and right ventricular myosin isozymes were examined by electrophoresis on pyrophosphate gel. The results showed the followings: 1) In the CT and the AT groups, the citrate synthase activities of the plantaris muscle were increased by 26% compared with the CS group (p<0.05) . 2) In the CT group, the running training had no effect on the myosin isozyme composition, in both ventricular muscles. 3) In the AS group, the atenolol treatment resulted in a decrease in the proportion of the V1 myosin and in an increase in that of the V3 myosin. Therefore, the proportion of the β-myosin heavy chain (MHC) in both ventricles of the AS group showed a significant increase compared with the CS group (p<0.05) . 4) The AT group showed a marked increase in the proportion of the β-MHC in both ventricles, compared with that of the AS group, especially in the left ventricle (p<0.05) .
From the results presented here, we did not observe any effect of the sympathetic nervous system on cardiac myosin isozyme composition in the running-trained rats.
It is generally accepted that hemodynamic overload results in an increase in the proportion of β-MHC, and in contrast, the stimulation of the sympathetic nervous system induces an increase in α-MHC. Therefore, we speculated that the effect of running training on cardiac myosin isozyme composition was induced by the effects of both the sympathetic nervous system and hemodynamic overload. Consequently, running training had apparently no effect on myosin isozyme composition.

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The purpose of this study was to determine the physiological responses, stroke rate and stroke length of front crawl leg kick and arm stroke of age-group and college swimmers and to elucidate the characteristics of male age-group swimmers, which have not been highlighted adequately. The subjects were ten 11.8-to 12.4-year-old well-trained male elementary school swimmers (group E) and nine 20.1-to 21.1-year-old well-trained male college swimmers (group C) . All the subjects were categorized into similar swimming levels for their ages. All the experiments were performed in a swimming flume (AQUAGYM made by IHI) . The water velocities during leg kicking and arm stroking were 60 and 70%, respectively, of the maximal velocity at maximal oxygen uptake (Vmax) . The oxygen uptake (VO₂), heart rate (HR), pulmonary ventilation (V_E), tidal volume (TV), respiratory rate (RR) and blood lactate (BL) level of each group were significantly higher during leg kicking than arm stroking at both velocities. VO2, V_E; and TV were significantly higher in group C than group E during leg kicking and arm stroking at both velocities, but HR, RR and BL did not differ significantly. The leg kick to arm stroke VO₂ ratio at 70% Vmax was significantly higher in group E than group C. The stroke rate at the same velocity was significantly lower and the stroke length was significantly higher in group C than group E, but the kick rate and length did not differ significantly. VO₂·SR^-1 and VO₂ KR^-1 at both velocities were significantly higher in group C than group E. VO₂ Wt^-1 SR^-1 at 70% Vmax was significantly higher in group C than group E, but VO₂ Wt^-1 KR^-1 at both velocities was significantly lower in group C than group E. These results clarified the differences between group E and group C, which must be considered carefully when designing a training program for age-group swimmers.

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In order to assess the effectiveness of exercise conditioning from the standpoint of physical health, exercise-induced changes in the blood pressure (BP) and vital age (VA: an index of physical health and/or aging status) were investigated in 27 Japanese female patients with essential hypertension. They were allocated either to the experimental (E, n =18; 50.1±7.5 years) or a usual-care control (C, n=9; 51.7±9.6years) group, according to their willingness. VA was derived from 11 physical and physiological parameters measured during exercise and at rest. The E group participated in a 4-month supervised exercise conditioning program with the intensity set at the lactate threshold level for 90 to 120 minutes twice a week and practiced self-controlled aerobic conditioning three times a week. The systolic (BPs) and diastolic (BPd) blood pressure of the E group decreased significantly from 160.6 ± 12.5 to 147.3 ± 12.9 and from 97.2 ± 10.1 to 89.3 ± 12.0 mmHg, respectively. Although the mean VA (60.4 ± 9.7 years) of the E group was significantly higher than the mean pre-conditioning chronological age (CA), it was reduced significantly (54.4 ± 11.8 years) post-conditioning. Furthermore, the VA change correlated significantly (r=0.74) with the BPs, but not the BPd, change. No changes were observed in the C group. We concluded that (1) exercise conditioning improves not only the BP, but also the overall physical health status, of patients with essential hypertension and (2) the change in the health status induced during the 4-month exercise program was closely associated with the BP change.

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Based on the maximal oxygen intake (VO₂max), 24 male students were classified into high (H-G), middle (M-G) and low (L-G) groups of the VO₂max level. In each VO₂max level group, thermoregulation characteristic values during cold exposure at an ambient temperature (Ta) of 12°C were compared with several parameters of cold-induced vasodilation (CIVD) measured at 28°C (observation 1) and the parameters measured after 30 min from the start of 60-min cold exposure (observation 2) . The relationship between CIVD as a peripheral vasomotor regulation response, and autonomic thermoregulatory response was examined. The results are as follows:
A . H-G showed the smallest decreases in the rectal temperature (Tre) and in mean skin temperature (Tsk), and these parameters decreased as VO₂max decreased. Enhancement of metabolic heat production (M) was highest in H-G and lowest in L-G.
B . In the observations 1 and 2 of the CIVD tests, mean skin temperature (MST), temperature at first rise (TFR) and resistance index (RI) increased with rise in VO₂max, while time of temperature rise (TTR) decreased. In the observation 2, TFR remained low by decreased temperature before water immersion (TBI) and, with TBI taken into consideration, no significant change in RI was observed except only in L-G.
C. MST, TTR and RI in the CIVD measurements (observation 1 and 2) were significantly correlated with the mean thermoregulation characteristic value during 30-60 min after the start of cold exposure (the second half period) .
D. During the second half period of cold exposure, significant negative correlations were observed between Tsk and body fat% (BF%) and between M and BF %. VO₂max was significantly correlated with RI, Tre, Tsk and M.
These results indicate that difference in physical fitness for endurance is clearly reflected in the values of cold-induced vasodilation in thermoneutral zone and during cold exposure. The peripheral vascular resistance of finger increased during cold exposure from that in thermoneutral zone causing decrease of finger skin temperature. After that, due to hunting reaction, the peripheral vascular resistance decreased, and a correspondance was observed between effectiveness in raising finger skin temperature through increase in skin blood flow and physical fitness for endurance. An interrelation was observed between the local cold resistance of peripheral vasomoter during exposure of finger to ice water and the whole cold resistance of autonomic temperature regulation during cold exposure of the whole body. It may be inferred that the subjects with high physical fitness for endurance have low insulative of body fat but have good cold tolerance by enhancement of heat production and preservation of skin temperature.

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The purpose of this study was to investigate the mechanism of the dynamic morphological change of the femoral extensor evoked by contraction.
In this study, the morphological changes during contraction and relaxation of the femoral extensor were analysed using MRI, and, the centers of gravity of the entire extensor group and of each extensor component were calculated using a pattern analyzer. The subjects were 10 female college basketball players, aged 18 to 22 years, with no history of knee injuries.
The results were as follows:
1. The shift of the center of gravity of each component was very characteristic.
2. The greatest dynamic morphological change was observed in the middle of the femoral extensors when the most muscle volume was involved, and the muscles were at their maximal volume.
3. During muscle contraction, obvious anterior protrusion of the muscle belly of each component of the quadriceps femoris was observed. The muscular force may be transferred effectively into the patellar tendon insertion.

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The purpose of this study was to detemine the effect of water intake on themoregulatory response during a round of golf (18 holes) in the heat (30-33°C, 55-70% RH) . Ten middle-aged male subjects participated in two separate golf rounds. During the first round the subjects played without fluid replacement (D), while in the second they received water replacement equal to weight loss in D (R) . With D, body weight loss of 3.8% was accompanied by a 13.3% reduction in calculated plasma volume (PV), while a small loss of body weight (0.5%) with an increase in PV of 4.6% was observed in R. A third round of golf by 5 of the subjects in cooler weather (20.4°C) without fluid replacement two months later resulted in heart rate and rectal temperature changes only slightly lower than during R. Golfing with D significantly elevated rectal temperatures and heart rates as compared to R. The rectal temperatures and heart rates at end of the 4.5-hr rounds were 39.4°C and 145 bpm, and 38.6°C and 116 bpm, in D and R, respectively. The serum enzymes, aspaartate aminotransferase, alamine aminotransferase, lactate dehydrogenase, and creatine kinase were measured at rest and after golfing. All enzyme levels increased signijicantly after golfing in D and to a lesser extent in R. The advantages of frequent fluid replacement during golf in high environmental temperatures was clearly demonstrated.

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A longitudinal study was conducted to determine the physical maturity characteristics of athletes engaged in the following extracurricular sports activities over the three-year junior high school period: basketball (N=40), baseball (N=130), volleyball (N=54), soccer (N=86) and a non-athletic group (N=37) which did not participate in sports.
Each athlete's maturity was determined from the age of maximum increment in height (MIA) of each individual. Longitudinal stature measurements were recorded annually in April for 12 years period from 6 to 18 years of age.
The study yielded the following results:
1. The MIA distributions of all the sporting groups were distinctly larger than that of the non-athletic group, increasing with each chronological age step on the distance curve and annual increase in height curve. The MIA mean value for the soccer group was significantly higher (P<0.05) than those of the non-athletic and all the other sporting groups.
2. The soccer group was significantly slighter (P<0.05) in stature than all the other sporting groups.
3. Subjects who played baseball throughout high school reached physical maturity earlier than those who only played throughout junior high school. However, those who continued to play soccer throughout high school reached maturity later than those who only played throughout junior high school.

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The purpose of this study was to investigate the effects of running training on bone formation in rats in relation to the age training started. The first experimental period was set from 6 to 12 weeks (wks) old and the second from 12 to 19 wks old. Sixty-four Wistar strain 6-wk-old male rats were initially divided into a non-exercise (N) and an exercise (E) group. At 12 wks old, each group was subdivided into two groups, providing four groups: non-exercise·non-exercise (NN), non-exercise·exercise (NE), exercise·non-exercise (EN) and exercise·exercise (EE) . Exercise consisted of treadmill running at a speed of 30 m/min, 60 mm day, 5 days wk. The animals were sacrificed before the experiment (6 wks old), post-first experiment (12wks old) and postexperiment (19 wks old), the bilateral tibiae were removed and their lengths, bone mineral content (BMC), bone mineral density (BMD) and bone histomorphometric parameters were measured. The tibial length was significantly shorter in 12-wk-old E than N rats and in 19-wk-old EE than NN. At 19 wks old, the total tibial BMD values were significantly higher in EE than NN, and the BMD values of the proximal and distal tibiae, where the cancellous bone was the main component, had increased markedly, whereas no differences between the diaphyseal BMD of each group were noted. Bone histomorphometry at 12 wks old, considered the immature period, showed that the osteoid surfaces and labeled surfaces tended to be increased by running training, but the bone volume was unchanged. In contrast, at 19 wks old, considered the early mature period, the osteoid surfaces showed a tendency to decrease and labeled surfaces to increase and consequently the bone volume increased albeit not significantly. These results suggest that: 1) running training started in immature rats represses longitudinal tibial growth, 2) the cancellous bone is more sensitive then the cortical bone to this type of training and 3) training of early mature rats increases bone volume by increasing the efficiency of osteoid calcification.

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In order to get basic data for preventing heat stroke accident during exercise in a hot environment, we analysed the relation between environmental temperature, and drinking and sweating. We also analyed the effect of water intake on body temperature regulation during exercise.
The environmental temperature started to rise in April, reached the maximumin August, and then decreased. Water intake and sweating increased significantly with increase in WBGT, but there was no correlation between weight loss and WBGT. The rise in body temperature during exercise (0.52±0.080°C) was constant and independent of WBGT. The rise in oral temperature during exercise was affected by the water intake and it was significantly higher when water was not supplied than that with water supply (p<0.001) . Sweat rate was significantly greater when water was supplied than when it was not supplied (p<0.01) .
The above results suggest that the amount of water intake increased with the increase in WBGT, which guarantees the increase in sweating and as a result maintenance of constant oral temperature.
Therefore it is suggested that it is better to supply water during exercise to facilitate evaporative heat loss, which prevent rise in oral temperature.

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A study was conducted to examine ; first, the cardiac response caused by various breath holding maneuvers, body water immersion and underwater swimming (US) ; second, the reproducibility of cardiac response in us; and third, the blood component variations caused by us. Water temperature used was 30°C. Fourteen healthy adults of both gender participated in this study. The results were as follows:
1. Those with stronger bradycardial response to apneic facial immersion (AFI) were subject to induced cardiac arrhythmias during or after us. And those with cardiac arrhythmias caused by AFI were inclined to produce a similar response even when their whole body was immersed as well as during us. Thus the test usingAFI proved to be valuable.
2. Heart rate of almost all subjects repeatedly showed a convex pattern, and their response to cardiac arrhythmias during and after us corresponded fairly accurately. Therefore it is presumed that cardiac function under the influence of US could be reproduced to some extent.
3. During static maneuvers, mainly bradycardiac arrhythmias were detected, including 2°AV block Wenckebach type in case of head out water immersion. On the other hand, brady, tachy and a combination of both were detected under us. From these findings and considering that the subjects with cardiac arrhythmias showed significant and specific variation of blood electrolyte and lactate, it was believed that various factors, including non-reciprocal increase of autonomic activities, the variations of blood component and so forth, simultaneously and interactively caused the cardiac arrhythmias during US.

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The long term effects of 17β-estradiol on the enzyme activity, wet weight, and fiber composition of the slow soleus (SOL) and fast extensor digitorum longus (EDL) muscles of ovariectomized and exercise-trained rats were examined. Female Wistar strain rats were divided into six groups: ovariectomy (OVX), OVX pluse loading exercise, 17 β-estradiol replacement after ovariectomy (E₂), E₂ pluse loading exercise, sham treatment (sham), and sham pluse loading exercise. A small animal treadmill was used for endurance training (speed, 25 m/min ; grade, 0 degrees ; frequency, 4 days/week ; running time, 0.5 hr/day ; duration, 13 weeks) . When the E₂ group were subjected to the exercise, the wet weight of the SOL, which had been decreased by ovariectomy, was increased, and recovered to the control level. The activity of phosphofructokinase (PFK), a glycolytic enzyme, of the SOL in the OVX group was lower than that in the E₂ and sham groups, and the activity was significantly increased (p<0.01) following exercise. The activity of succinate dehydrogenase (SDH), an oxidative enzyme, of the SOL in the OVX group was significantly decreased (p<0.05) compared to that in the E₂ group. The SDH activity of the SOL in the OVX and E₂ groups increased, but not significantly, after endurance exercise compared with the level in the sham group. In the EDL, on the other hand, no clear correlation between oxidative and glycolytic enzyme activity was shown in any group, even in the exercise groups. The number of type II fibers in the SOL, classified histochemically with myosin ATPase, also increased, but not significantly, after exercise in the OVX group compared with findings in the sham group. These results suggested that 17 β-estradiol replacement combined with endurance training effectively maintained the function of slow muscle in ovariectomized rats.

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This study was conducted to determine the effect of exercise training in water (water exercise) in sedentary obese women. Twenty-three women, aged 23-58 years (mean±SD 41.7±11.7), partici pated in this study. Any volunteer with diagnosed disease or taking prescribed medication that might influence the outcome of this study was excluded from participation. The women were allocated either to the exercise group (n =15, weight =65.2±12.3 kg, %body fat=39.2±7.0%) or the control group (n = 8, 62.4±8.3 kg, 34.0±2.4%), respectively. The exercise program consisted of dynamic movements for 60 minutes per session, three days per week for 16 weeks. The exercise intensity was set at approximately 65% of the age-related maximal heart rate. The attendance rate on the program was 89.2±3.0%. The body mass and %body fat of the exercise group decreased significantly by 4.7±1.9 kg (P<0.05) and 3.6±2.4% (P<0.01), respectively, compared with the preexercise values. Significant improvements in their aerobic capacity, trunk flexibility and vertical jump (P<0.05) were also observed. Their energy intake and the amount of other daily physical activity remained essentially unchanged throughout the study. No significant changes in any of the parameters measured occurred, in the control group. These findings indicate that water exercise improved the body composition and physical fitness of obese women.

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To estimate how much physical activity is needed to improve overall health status in female patients with ischemic heart disease (IHD), the dose-response relationship between the duration of daily aerobic exercise and change in vital age (VA) was assessed for 4 months of exercise training. VA was considered as an index of physical health status and was computed from various coronary risk facotrs and physical fitness elements. Eighteen female patients with IHD, aged 54.3±9.1 yrs, continued the supervised exercise training 1-2 d/wk and the self-controlled exercise training 1-5 d/wk for 4 months. The intensity of exercise was set at individually determined lactate threshold. Daily duration of aerobic type exercise calculated for each patient averaged 21.1±11.0min/d, rang ing from 4.6 to 46.7 min/d. After the 4-month exercise training, VA decreased from 59.6±12.1 yrs to 54.2±11.8 yrs (P<0.05) . Significant correlation was found between daily duration of exercise and the change in VA (Spearman's rho=-0.60 ; Pearson's r=-0.62) . In this relationship, 10 min/d of exercise induced the decrease in VA and no further decrease in VA was found over the 30 min/d of exercise. In the 11 variables which constitute the equation of VA, oxygen uptake at lactate threshold (Spearman's rho=0.65; Pearson's r=0.64) and balancing on one leg with eyes closed (Spearman's rho=0.48; Pearson's r=0.51) significantly correlated with daily duration of aerobic exercise. From these results, it is suggested that the amount of moderate intensity exercise required to improve physical health status in female patients with IHD may be 10-30 minutes per day.

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The effects of chronic overload by synergist ablation (SA) on fiber type, myosin heavy chain (MyoHC) isoforms, and contractile properties in the rat plantaris muscle were studied. Plantaris muscle was overloaded by bilateral removal of its synergist of gastrocnemius muscle in Fischer 344 female rats (aged 8 weeks) . Muscles of sham-operated legs served as controls.
The overloaded plantaris was 20% heavier than control 3 weeks after SA. Overload by SA resulted in remarkable increases in cross-sectional areas of muscle fibers of all types ; however, the percentage increase was less in type II b fibers. Twitch contraction and half-relaxation time before and after tetanus did not change, but fatigue resistance increased significantly with overload. The percentage of area occupied by type II b fibers, which have lower oxidative capacity, decreased while the percentage of area occupied by other type II fibers, but not type I fibers, increased. Analysis of MyoHC isoforms with gradient sodium dodecylsulfate polyacrylamide gel electrophoresis revealed a decrease in II b isoforms and an increase in II d isoforms.
These results suggest that chronic overload produces changes in muscle fiber type and MyoHC isoform compositions which partly account for increased fatigue resistance in overloaded muscles.

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This study clarified the most appropriate landing motion for enhancement of the rebound drop jump index (RDJ_index), which can evaluate the ability to perform ballistic and stretch-shortening cycle (SSC) movements. The RDJindex was calculated using the formula RDJ_index= (1/8⋅g⋅RDJt_a²) /RDJt_c where RDJt_c and RDJt_a are the contact and air times during a rebound drop jump from a height of 0.3 m (RDJ), a typical SSC movement. The relationships between the RDJ_index and the characteristics of the knee and ankle joint motions during RDJ were examined in nine male jumpers. The results were as follows:
(1) The characteristics of leg motion during the descending phase were that the ratio (%K-ANG) of displacement in flexion of the knee during the descending phase to that during both descending and takeoff phases was 48.6% and this preliminary motion started 53.6 ms before touchdown. Furthermore, as %K-ANG increaced, the contact time decreased (r=-0.784, p<0.05), the air time increased (r=0.874, p<0.01) and consequently, the RDJ_index increased (r=0.891, p<0.01) . These results suggested that quick knee flexion just before touchdown is an important factor in increasing the RDJ_index.
(2) A characteristic of the leg motion during the takeoff phase was that the end point of knee flexion appeared 13.3 ms earlier than that of ankle dorsiflexion. That time increased as %K-ANG increaced (r=0.830, p<0.01), but conversely, as %K-ANG decreased markedly, end point of ankle dorsiflexion appeared earlier than that of knee flexion. These results suggested that preliminary motion of the knee would result in appropriate timing of the knee and ankle motions for shock absorption during the takeoff phase of RDJ.
(3) An other characteristic of the leg motion during the takeoff phase was that the ratio of displacement of the knee in extension to that in flexion was 310.2%. This ratio increased as %K-ANG increaced (r=0.903, p<0.001) . These results suggested that preliminary motion of the knee would cause to increase displacement in extension for kick motion and yet to decrease displacement in flexion for shock absorption.
These findings led to the conclusion that quick and short range flexion at the knee just before touchdown was an effective landing motion for enhancing the ability to perform ballistic and SSC movements.

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The purpose of the present study was to investigate the effect of maximal interval training for 10 weeks on arterial oxygen saturation (SaO₂) and ventilatory response during heavy exercise. Seven subjects volunteered for participation in the study. All subjects performed an interval training 4 days per week. Training protocol per day consisted of five periods of exercise of 3-min duration on a cycle ergometer at a power output on 100% maximal oxygen uptake (VO₂max), interspersed with 2-min recovery cycle at 50%VO₂max. VO₂max and ventilatory data measured every week. SaO₂, end-tidal oxygen partial pressure (PETO₂), end-tidal carbon dioxide partial pressure (PETCO₂) and the ventilatory equivalent for oxygen (VE/VO₂) measured during 5-min heavy exercise at 90%VO₂max every other week. VO₂max significantly increased from 52.5±4.9 to 60.6±5.8 ml⋅ml^-1⋅kg^-1 during the training. SaO₂ reduced significantly from 95.4±1.1 to 93.3±1.8%, similarly PETO₂ and VE/VO₂ reduced during the training. A significant positive correlation was found among SaO₂, PETO₂ and VE/VO₂ during heavy exercise (SaO₂-PETO₂, r²=0.48, P<0.05 ; SaO₂-VE/VO₂, r²= 0.49, P<0.05; PETO₂ - VE/VO₂, r²=0.81, P<0.05) . These results suggest that-50% of the arterial O₂ desaturation during heavy exercise can be accounted for by low ventilatory response. Therefore the maximal intervsal training induced arterial O₂ desaturation during heavy exercise, which can be half explained by low ventilatory response.

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Effects of various tetanic stimulation frequencies (50 Hz, 100 Hz and 200 Hz) on the time course of twitch potentiation were examined in the adduction of human pollicis. Isometric twitch tension curve and surface electromyogram were recorded immediately after (1 sec) the 10 sec-tetanus and at intervals of lOsec (up to 300sec) . The stimulating methods were by nerve and direct stimulations in order to examine the role of nerve on the post-tetanic potentiation. The results were summarized as follows :
1) The greatest potentiation was observed immediately after the tetanus. The potentiation decreased rapidly in the period of 60 sec after the tetanus. Then, the potentiation continued to decrease at the low frequency (50 Hz) ; however, it tended to level off at the high frequencies (100 Hz and 200 Hz) .
2) The time course of twitch potentiation by the nerve stimulation was larger than that by the direct stimulation. This result suggests that nerve has a factor which enhances potentiation. The duration of the potentiation varied according to the stimulation frequencies by the nerve stimulation. It seems that this phenomenon was strongly influenced by the nerve.
3) The degree of increase in twitch tension tended to depend greatly on the peak rate of force development. This result suggests that the increase in twitch tension was closely related to the intensity of the active state.
4) Time course of time to peak tension relatively corresponded to the half relaxation time. It seems possible for the duration of the active state to be related to calcium uptake at the sarcoplasmic reticulum.
5) The coupling efficiency by the direct stimulation tended to be smaller than that by the nerve stimulation after 10 sec. This result suggests that the stimulating nerve possesses a factor which prolongs the period of potentiation.

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Unfortunately, anabolic androgenic steroid (AAS) abuse is prevalent in Japan. Most steroid abusers are amateur bodybuilders, powerlifters, wrestlers, and “fitness enthusiasists.” The case presented is of a young amateur bodybuilder, who suffered gynecomastia, whose only significant risk factor was his nonmedical use of an AAS.
A 27-yr-old male was admitted to our hospital in December 1992 with gynecomastia. He reported starting to use an AAS, oxymetolone (Anadrol^®) 30 mg daily, at the age of 23 yrs in 1987. He had developed bilateral painful gynecomastia, impotence and decreased sex drive within 3 months of starting AAS use. He stopped using it, and was admitted to another clinic in 1991. He took testosterone propionate (Testinon^®) 25 mg weekly, but, as he was anxious about the long-term use or this medication, he was adimitted to our clinic.
On physical examination his gynecomastia had diminished slightly, but he still had breast tenderness. All his laboratory examination results were almost within the normal ranges. Neverthless his serum free testosterone level was slightly low, so he took tamoxifen (Nolvadex^®) and Chinese medicines. Consequently, his gynecomastia improved after treatment, for 5 months.
Gynecomastia develops when an AAS is converted to estrogen. In conclusion, tamoxifen administration may be useful to reverse gynecomastia caused by AAS doping in sportsmen.

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