The purpose of the present study was to investigate the relations between force and time to peak force or force developing speed during various levels of the fastest isometric volntary contractions on several muscle groups. Force curves of knee extension, knee flexion, and elbow f1exion were recorded on 17 ma1e subjects during maximal (MVC) and submaximal force which were exerted as fast as possible. Then, peak force, time to peak force, and force speed were measured. Larger MVC muscle grups tended to take longer time to reach MVC among those three muscle groups. The significant relation between MVC and time to MVC was obtained in knee flexion and elbow flexion but not for knee extension. The relation between force and time to peak force was changed at 50% of MVC. Though the time to peak force was almost constant below 50% of MVC, the time to peak force increased with increment of force amplitude above 50% of MVC. Though force speed increased with increment of peak force, this relation changed at approximately 50% of MVC. The increment was less in the force speed accompanied with force increment above 50% of MVC. From these results for the examined muscle groups, it was concluded that change courses of time to peak force and force speed which accompanied with force graduation were different between be1ow and above 50% of MVC when the fastest isometric voluntary contractions were performed. It was suggested that different modes of central mechanism would be operative between below and above 50% of MVC.

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We examined the metabolic and ventilatory responses of 7 less experienced marathon runners to a 2-hr run at the race pace simulated from an actually completed marathon performance. Maximal oxygen uptake (VO₂max) and lactate threshold (VO₂@LT) measured on a treadmill 1 wk prior to the marathon competition, averaged 61.7±4.7 ml · kg^-1·min^-1 and 44.9±3.0 ml · kg^-1· min^-1, respectively. The running at the marathon race pace elicited an average VO₂ of 2.65±0.48 l · min^-1 or 44.1±:5.6 ml · kg^-1·min^-1 during the first 10 min immediately after starting the running, which corresponded to approximately 71.0±4.7% of VO₂max, and increased by only 0.05 to 0.10 l · min^-1(<4%) throughout the remainder of the running. The periodically observed blood lactate concentration remained virtually unchanged, indicating the rate of lactate removal did not differ from its appearance. It is concluded that, even in less experienced runners, almost steady state VO₂ and lactate responses do occur during prolonged running at the marathon race pace or the race pace relative to LT.

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The influence of load by maintaining isometric muscular contraction till exhaustion to microvibration (MV) on m. biceps brachii was studied with the use of MV sensor (MT-3T, acceleration type). The amplitude of MV was calculated with both band pass filter and integrator, while the frequency of MV was analyzed by Fourier transform and the power spectrum was obtained. It was found to be reasonable that the effective load to the muscle was evaluated not by the force but by the momentum which was the product of the force and endurance time till exhaustion.The momentum which corresponded to holding the force less than 25 %MVC (maximum voluntary contraction) till exhaustion increases the amplitude by about 40%, as compared with that at rest state. The augmentation of the momentum also increases the change of the peak frequency. The results indicated that MV as well as electromyogram could be applied to the evaluation of muscular fatigue in isometric contraction.

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Associations between alterations in endurance running performance and alterations in cardiorespiratory fitness, body composition, serum lipids, and hematological variables were evaluated in 18 healthy males (age: 28.3±5.5 years, stature: 170.6:±5.1cm, weight: 62.7±6. 3kg). Analyses of the daily training records indicated that the subjects trained 3.4±0.8 d·wk^-l for an average period of 3.8 months and the average jogging/running distance was 3.5±1.2 km·d^-1. The intensity of the training was gradually increased from 60% up to 75% of the pre -training VO₂max. Major effects of the moderate intensity training were significant improvements in VO₂max, VO₂@LT, and 5km run time. In addition, diastolic blood pressure and heart rate (HR) decreased significantly from the pre-training to the post-training, while hemoglobin concentration and mean corpuscular volume increased siguificantly. Both in the pre-training and the post-training, VO₂max and O₂@LT showed a correlation of higher than r=0.7 with 5km run time. When the association between the absolute amount of change (A) in the 5km run time and A in VO₂max or VO₂@LT was evaluated, no significant correlation existed. The relatively close associations of △triglycerides (r=0.665), △HR (r=0.516), and △weight (r=0. 497) with △5km run time observed in the present study need to be clarified in future studies. Increased and/or more efficient lipid utilization or improved cardiac function after a relatively short period of endurance running training in normal men remains only speculative as a critical factor of endurance performance changes.

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The purpose of this study is to investigate the change of the electromyogram (EMG) and the heart rate (HR) during static work on the different body surface pressure areas by wearing a pressure suit which can apply pressures to the human body surface by the individual regions. The EMG of the m. flexor carpi ulnaris, m. biceps brachii during the upper extremity work (UEW) and the m. vastus lateralis during the lower extremity work (LEW) were measured for 4min.. The subjects flexed their arms (UEW) or legs (LEW) at the elbow or knee joints angle to 90 degrees with the load of 25%MVC of the m. biceps brachii or m. vastus lateralis respectively. The pressure applied was 10mmHg in both works and 30mmHg (UEW) or 40mmHg(LEW). The pressure time intervals before work was 3min. and 40min., The EMG of the working muscle in the both works was increased when high pressure was applied to the region containing the working muscle. When pressure was applied to the whole body, the increase of the EMG was not siguificant compared with that of the control value (non -pressure). The HR was not increased in every condition compared with that of control.

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The purpose of this study was to investigate the relationships between fatigue curves of muscular power and muscle fiber composition, and between the force-velocity properties and muscle fiber composition when performed powerful contractions at maximum effort in certain load. Subjects were 11 healthy adult male whose ages ranged between 22 and 61 years old. The produced muscular power measured when subjects were required to perform 100 consecutive maximum leg extensions at every 3 seconds using an improved inertia wheel ergometer with an equivalent mass of 529.3kg. Muscle fiber samples were obtained from the ventral part in m. vastus lateralis with needle biopsy technique. Fiber types were classified as fast twitch fiber (FT) and slow twitch fiber (ST), further more FT fiber was divided into FTa and FTb subgroups. Following is the results obtained in this study. 1) The abrupt reduction in muscular power around 40th to 50th consecutive maximum contraction was thought to be mainly due to the fatigue in FT fiber, especially in FTb fiber. 2) Significant correlation (r=0.613, p≤0.05) was obtained between the degree of regression line of force-velocity properties and %FT. This seemed to suggest that the higher the person's %FT was, the more the reduction in muscular power was affected by the decrease in the velocity component.

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Correlation between HR and VO₂ during video watching was studied in comparison with that during bicycle ergometer working. Five healthy males volunteered as subjects. Subjects watched video program for 60 minutes and worked on a bicycle ergometer with incremental work loads of 25 W/2 minutes for 13 minutes. VO₂ was significantly correlated with HR in both conditions, but the correlation coefficients and slopes of regression lines were lower in video watching than in bicycle ergometer working. Estimated energy expenditure during video watching from HR, based on the HR-VO₂ regression of bicycle ergometer working, was 111% of the measured value. It was suggested that estimation of daily energy expenditure using HR -VO₂ regression of dynamic work tend to be overestimated when daily life includes much mental work.

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