A study was performed to clarify the effects of endurance training above the anaerobic threshold (AT) on the isocapnic buffering phase during incremental exercise in athletes. Eight middle-distance runners aged 19.6±1.2 years performed incremental exercise testing with a modified version of Bruce's protocol. After a 6-month high-intensity interval and paced running training at levels above AT, maximal oxygen uptake (VO₂max) (ml⋅ kg^-1⋅min^-1) was significantly increased from 60.1±5.7 to 64.7±5.5 (p<0.05) . AT (m⋅lkg^-1⋅min^-1) was slightly but significantly increased from 28.2±3.5 to 29.6±4.3 (p<0.05) . The respiratory compensation point (RC) (ml⋅ kg^-1⋅min^-1) was markedly increased from 53.0±8.3 to 57.7±8.2 (p<0.05) . Although neither the slope of the first regression line below AT (S1) nor that of the second line above AT (S2) calculated by V-slope analysis was altered, the range of isocapnic buffering (ml⋅kg^-1⋅min^-1) from AT to RC was significantly extended from 24.8±5.9 to 28.1±6.0 after the 6-months of training (p<0.05) . In addition, the amount of change in VO₂max after the 6-month of training period (ΔVO₂max) was correlated with Δisocapnic buffering (R=0.72, p<0.05) . We conclude that the degree of increased respiratory compensation point is larger than that of AT after high-intensity endurance training at levels above AT, and that the range of isocapnic buffering may be an important factor in relation to the increase in the maximal aerobic capacity of athletes.

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To investigate the effect of intense exercise on immunological factors in saliva, we measured secretory immunoglobulin A (sIgA), lactoferrin and fibronectin. We used a reliable saliva collection method that has already been reported. Timed saliva samples were obtained from 16 healthy young males. Samples were collected before, immediately after, 1 day after and 5 days after endurance running (42.195 km) . The concentrations (μg/ml) of sIgA, lactoferrin and fibronectin were measured by ELISA, and the secretion rates (μg/min) of each were calculated. Immediately after the exercise, the concentration of total protein in saliva increased significantly, but the sIgA secretion rate decreased to 53%. The secretion rates of both lactoferrin and fibronectin did not change significantly. The local immune system plays an important role in mucosal surface defense against upper respiratory tract infection. The sIgA level in the oral cavity was temporarily decreased after intense exercise. A decreased sIgA secretion rate might partly explain the increased susceptibility to upper respiratory tract infection after endurance exercise.

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Effects of short-term, high-intensity and long-term, moderate-intensity exercise on biochemically assessed sarcoplasmic reticulum (SR) ATPase protein were analyzed in muscle homogenates of the rat after treadmill runs to exhaustion (avg, time to exhaustion 2 min 48 sec and 1 h 29 min, respectively) . The exercise-induced changes in SR Ca²⁺ -ATPase activity were muscle type-specific. After short-term exercise, a decrease in the activity occurred in the soleus muscle and the superficial region of the vastus lateralis muscle whereas long-term exercise depressed the rate of ATP hydrolysis in the soleus muscle and the deep region of the vastus lateralis muscle. The concentration of fluorescein isothiocyanate, a competitor at the ATP-binding site, for 50% inhibition of SR Ca²⁺ -ATPase activity fluctuated only in the soleus muscle subjected to short-term exercise ; it was increased by 31%. This change occurring in the soleus muscle would elevate SR Ca²⁺ -ATPase activity at a given concentration of ATP. The results presented here suggest that acute short-term exercise to exhaustion may exert a remarkably inhibitory factor on SR Ca²⁺ -ATPase protein of slow-twitch muscle, which can overcome the positive effect probably arising from the phosphorylation of the phospholamban.

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The purpose of this study was to investigate the physiological responses during pushing of a racing-wheelchair. Five subjects with spinal cord injury (T4-L1) participated in two experiments. In the first experiment, the subjects pushed a racing-wheelchair mounted on a roller. Pulmonary ventilation (VE), oxygen uptake (VO₂), heart rate (HR), blood lactate concentration (LA), and rating of perceived exertion (RPE) were measured to examine the physiological responses during submaximal and maximal tests of wheelchair exercise. The mean value of %VO₂max at ventilatory threshold (VT) was 60.7±5.3%. VO₂ increased curvilinearly with speed, and HR increased with speed, forming an S-shape. HR increased linearly with increasing VO₂ before the VT, then showed a steeper parabolic rise to almost maximum, followed by a flat phase. In the second experiment, during 1500-m and 5000-m wheelchair races and a half-marathon, VE, VO₂, and HR were measured to reveal the physiological characteristics of wheelchair racing as a competitive sport. During the 1500-m and 5000-m races by four subjects, the mean values of %VO₂max were 73.1±7.3% and 66.0±13.3%, respectively. During the half-marathon by one subject, %VO₂max reached 72.1%. These data suggest that wheelchair endurance athletes compete at very high intensity (over VT level) in wheelchair races.

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To determine whether fiber type-specific expression of heat shock protein (HSP, or stress protein) occurs in unstressed rat skeletal muscle, the medial gastrocnemius of adult female Sprague-Dawley rats was subjected to immunohistochemical analysis. Antibodies against 5 types of anti-myosin heavy chain (MHC) were used to classify the type of fibers, and 2 types of anti-HSP antibodies were employed to analyze the fiber type-specific expression.
Serial cross-sections of 10 μm thick cut by a cryostat were incubated with primary anti-MHC or anti-HSP 60 and 72 antibodies, followed by biotinylated secondary anti-mouse antibodies, and avidin-biotin complex solution. A peroxidase DAB substrate kit (Vector SK-4100) or BCIP/NBT solution was used to visualize the immunoreaction of each fiber type.
By using the 5 types of anti-MHC antibodies, fibers were classified into 4 types : slow-type I, fasttypes IIA, IIX, and IIB. Anti-HSP 72 antibody reacted with many, but not all, type I and IIA fibers, whereas anti-HSP 60 antibody reacted specifically with type I fibers. Neither type IIX nor IIB fibers showed immunoreactivity with anti-HSP 60 or 72 antibodies. These results suggest that the expression of HSP 60 protein is related to that of type I MHC, and that the expression of HSP 72 protein may be related to that of types I and ha MHC, in unstressed rat skeletal muscle.

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The change in R-R interval (RRI) induced by rapid postural change from a squat posture to standing was analyzed in 8 healthy male students (20.3±1.2 years of age) before and immediately after maximal running exercise. We instructed subjects to stand up as quickly as possible, and to repeat the standing-up movement three times at intervals of 2 min. Heart rate responses and heart rate variability were analyzed by the change in RRI induced by standing up. Heart rate (HR) increased quickly at the onset of standing up. The time (T) until the maximal HR (Hmax) was reached 9.79±1.44 s after standing up, and then the HR after Hmax decreased rapidly with time. The maximal HR was 1.20 times higher while standing up than in the squat position. Maximal running exercise significantly delayed the time taken to reach Hmax after standing up, and significantly diminished the increased HR to 1.15 times. The Hmax/Hmin ratio, which expressed the magnitude of autonomic activity during standing up, was significantly lower following maximal exercise, indicating that the cardiac sympathetic nervous system seems to be in a state of hyperfunction immediately after maximal running exercise. These findings suggest that disturbance in the postural adjustment of the cardiovascular system immediately after intense exercise may be induced by the delayed response and decreased amplitude of the HR.

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A study was conducted to examine activity patterns of surface electromyograms (EMGs) in the triceps surae muscles (medial gastrocnemius, MG ; lateral gastrocnemius, LG ; soleus, SOL) during isometric contraction in plantar flexion (60% MVC, 20% MVC) after immersion in water at three different temperatures. Seven healthy male subjects were immersed in water at 2-3°C (ICE), 19-21°C (MID), and 40-42°C (HOT) . The results of the study are summarized as follows :
1) In the MG and LG, there was a slight increase in the rate of integrated electromyograms (IEMGs) in the MG (the main agonist muscle) . However, the rate of increase in the LG, which is the synergistic muscle, was much greater than that in the MG when contraction was sustained at 60% MVC. Therefore, the activity pattern suggests that muscle activity in the LG compensates for that in the MG.
2) The IEMGs of the SQL with sustained contraction, increased significantly after immersion in HOT and MID, but the IEMGs decreased after immersion in ICE. These results suggest that the recruitment threshold in slow-type motor units should increase during sustained isometric contrac-tion in ICE.
As illustrated above, the activity of the LG increased to compensate for that of MG. In the SQL, muscle activity with sustained contraction decreased in ICE. These results suggest that control mechanisms of the central nervous system might play an important role in the associated movement of the triceps surae muscles.

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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.

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The purpose of this study was to clarify the characteristics of the gait function for the elderly with a special reference to the angle of the ankle joint and that of the metatarsophalangeal (MP) joint at heel contact and toe off. Five healthy young men (aged 22 to 23 yrs) and five healthy elderly men (aged 65 to 71 yrs) participated as the subjects in this study. The angle variation of the right ankle joint and that of the MP joint detected in goniometers were analyzed synchronously with the data of the force plate and the image data of bare foot movements during free, slow, and fast gait. The following results were obtained:
1. The walking speed, step length, and cadence for the elderly during free gait were significantly small. Furthermore, the step length of the elderly was shorter than that of the younger subject even with the same height. Moreover, it was found that the fluctuation in both the step length and cadence resulted in an fluctuation in walking speed.
2. One reason for the decrease in step length and cadence, and the increase in duration of the double supporting time for the elderly is the lowering of walking speed.
3. The angle of the ankle at heel contact, the angle of the ankle at toe off, and the angular displacement of the MP joint were significantly smaller for the elderly during free gait and during walking within a range of speeds. Also, the angle of the ankle at heel contact, and the angle of the ankle at toe off for young and elderly subjects were separated into two groups during walking within a range of speeds. It may be showed that the reason for the smallness of the angle of the ankle at heel contact and the angle of the ankle at toe off for the elderly irrespective of walking speed is due to an elderly behavior that unconsciously makes the angle smaller to prevent the danger of falling.
In conclusion, the difference in variables between young and elderly subjects during free gait and walking within a range of speeds exemplifies the characteristics of gait function for the elderly.

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Sprinting speed is the final result of sprinting movement. Though sprint runners always try to sprint as rapidly as possible, their speed changes with time. Such changes in speed are caused mainly by physical movement in the support phase of sprinting, because sprint runners encounter deceleration force and generate acceleration force in only this phase. Especially, the support leg has an immediate effect on the sprinting speed.
The purpose of this study was twofold : (a) to determine whether functions of the support leg segments change with changes in sprinting speed and the sprinting situation, and (b) to investigate the characteristics of changes in the functions of the support leg segments.
Ten male sprint runners (age 20.7±1.2 yr, height 1.72±0.06m, body mass 63.3±4.7 kg) participated in the study. Subjects performed three sprints from starting blocks, and were instructed to execute exhaustive sprint runs. Their movement patterns were analyzed for five support phases : (S1) at 77.4±3.1% of maximum sprinting speed (MSS) during the acceleration period, (S2) at 95.4±1.9% of MSS during the acceleration period, (S3) at MSS, (S4) at 94.1±1.4% of MSS during the deceleration period, and (S5) at 90.8±2.2% of MSS during the deceleration period. These phases were designed to allow comparison of movement patterns in different situations with equal sprinting speeds. The linear dynamics approach was adopted to determine the direct effects of segmental movement on the sprinting speed. This is based on the theory that the velocity of a segmental center of mass (SCM) is the vector sum of the velocity of the adjacent lower joint and the relative velocity of the SCM with respect to the adjacent lower joint.
The force acting on each segment of the support leg created a stereotypical pattern in spite of differences in sprinting speed and the sprinting situation. However, the support time and the magnitude of the force acting on the shank and the foot changed with the sprinting speed. The sprinting speed was closely related to impulses acting on the shank and the foot. In contrast, the magnitude of the force acting on the thigh remained unchanged. The impulse acting on the thigh was not related to the sprinting speed, but there was a close relationship between impulses acting on the thigh and the shank, and the foot.
In conclusion, (1) The performance of the function of the thigh remains unchanged in spite of differences in sprinting speed and the sprinting situation. The thigh always works to attain its task, which is to sprint as rapidly as possible ; (2) The functions of the shank and the foot have a direct influence on changes in sprinting speed. These changes are caused by changes in the magnitude of the forces acting on the shank and the foot, and the support time ; (3) While the function of the thigh does not affect the sprinting speed directly, it affects the functions of the shank and the foot. The function of the thigh thus has an indirect influence on sprinting speed ; (4) The thigh and the foot work to compensate for decreases in the performance of the shank during the deceleration period.

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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.

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