ABSTRACT
This study examined the relationship between riding posture and muscle activities during passive exercise on horseback-riding simulation equipment. The effects of passive training on the prototypes were also determined. Three prototypes with tilted seat (A110, A130, and A140) were developed with an attempt to change the angle between trunk and leg to 110, 130, and 140 degrees, respectively. Twelve female aged 42.7±2.3 years performed passive exercise on the three prototypes and isometric maximal voluntary contraction (MVC) tests. Electromyogram of nine muscles in the trunk and lower limb were recorded. On A110, back muscle showed the largest activity (22%MVC ; p<0.01 ; repeated measures ANOVA). Contrastingly on A140, abdominal muscle and knee extensor showed the largest activity (40%MVC and 26%MVC ; p<0.01). Passive training on the prototypes for 30 minutes/day, 4 times/week, 8 weeks produced enhancement of muscle strength in trunk and hip. Riding posture is an effective factor to control physical effects without increasing the velocity on horseback-riding simulation equipment.
ABSTRACT
The purpose of the present study was to develop a new method that enables individualized determination of the optimal exercise intensity for health promotion. Our study was based on the following observations : (1) physical activity at ventilatory threshold (VT) has been useful for enhancing physical fitness and even improving medical conditions such as heart failure, hypertension and diabetes, (2) exercise intensity at VT is characterized by suppressed vagal activity, and (3) vagal activity can be evaluated by analyzing heart rate variability (HRV) . In the first study we defined a criteria for determining the exercise intensity corresponding to VT using HRV analysis (heart rate variability threshold, THRV) . In 16 normal subjects, a time series of ECG RR interval were recorded and the means of the sum of the squared differences in successive RR intervals (MSSDs) were calcu-lated during a ramp exercise test with a cycle ergometer. Based on the values of MSSD and the dif-ferences in successive MSSDs (ΔMSSD) at the intensity of VT, we defined the criteria of THRV as follows : MSSD<25 msec<SUP>2</SUP>and ΔMSSD<6 msec<SUP>2</SUP>. Another exercise test with a cycle ergo-meter was performed to evaluate the relationship between THRV and VT in 63 normal subjects. Heart rate (HR) and oxygen uptake (VO<SUB>2</SUB>/wt) at THRV were 111.8±13.2 beats/min and 15.2±4.4 ml/kg/min, and HR and VO<SUB>2</SUB>/wt at VT were 116.2±11.6beats/min and 16.5±3.7ml/kg/min, respectively. There was a significant correlation between THRV and VT (HR : r=0.82, p<0.001, VO<SUB>2</SUB>/wt : r=0.88, p< 0.001) . Thus, THRV and VT provided almost identical exercise intensities. As a result, we propose that, similar to VT, THRV can be used as an indicator of the optimal exercise intensity suitable for health promotion in normal subjects.
ABSTRACT
The present study was designed to examine the effects of aerobic exercise on the change of alpha wave component in electroencephalogram (EEG) and plasma β-endorphin. Exercise consisted of 30-min cycling on an ergometer with the load adjusted to elicit a heart rate rise of 50% between resting and predicted maximal value. The EEG signals and blood samples were obtained before and after 30-min exercise. The EEG signal was digitized at a sampling frequency of 64 Hz and analyzed by means of computer-aided decomposition algorithm and frequency power spectral analyses, respectively. The blood samples were immediately centrifuged for 15-min for quantitative analysis of β-endorphin by means of radioimmunoassay method. Results indicated that β-endorphin was significatly (p<.05) greater after exercise as compared to that of the resting contorol. It was also found that the larger the changes in β-endorphin following exercise, the higher the appearance rate of alpha wave in EEG. There was a positive and significant correlation (r=563, p<0.05) between the increase in alpha wave component and that of the plasma β-endorphin. These results suggest that traquilizer effects of aerobic exercise could be explained, at least in part, by the increase of alpha wave component and plasma β-endorphin which in turn bring about the relaxation effects upon the central nervous system.
ABSTRACT
The present study was designed to examine the effects of aerobic exercise on the change of alpha wave component in electroencephalogram (EEG) and plasma β-endorphin. Exercise consisted of 30-min cycling on an ergometer with the load adjusted to elicit a heart rate rise of 50% between resting and predicted maximal value. The EEG signals and blood samples were obtained before and after 30-min exercise. The EEG signal was digitized at a sampling frequency of 64 Hz and analyzed by means of computer-aided decomposition algorithm and frequency power spectral analyses, respectively. The blood samples were immediately centrifuged for 15-min for quantitative analysis of β-endorphin by means of radioimmunoassay method. Results indicated that β-endorphin was significatly (p<.05) greater after exercise as compared to that of the resting contorol. It was also found that the larger the changes in β-endorphin following exercise, the higher the appearance rate of alpha wave in EEG. There was a positive and significant correlation (r=563, p<0.05) between the increase in alpha wave component and that of the plasma β-endorphin. These results suggest that traquilizer effects of aerobic exercise could be explained, at least in part, by the increase of alpha wave component and plasma β-endorphin which in turn bring about the relaxation effects upon the central nervous system.
ABSTRACT
Neuromuscular fatigability of different muscle groups was studied under various physiological conditions in eight healthy male subjects by means of EMG fatigue curve analysis (E/F ratio defined as the rate of rise in IEMG/force as a function of time) which has been commonly used.<BR>Under the experimental conditions and assumptions described in the present investigation, the following conclusions could be justified on the basis of the experimental results.<BR>1. The E/F ratio for the biceps brachii muscle was significantly greater (p<0.0005) than that of the soleus muscle at 40% of MVC, suggesting that the biceps brachii with presumably greater %FT fibers were consistantly more fatigable than their own soleus muscle.<BR>2. The exponential growth of the E/F ratio as a function of either the maximal sustaining time (T<SUB>s</SUB>) or different fractions of MVC suggested a possible neurophysiological link between the fatigability of the biceps brachii muscle and their MU activities which might increase in an accelerated fashion.<BR>3. The evaluation of static work capacity (W<SUB>s</SUB>) described in the present study revealed that the differences in the critical force level and Ws during free circulation and arterial occlusion could be explained by the relative availability of muscle blood flow which might determine the rate of energy reconstitution.<BR>4. The EMG data taken during a constant torque output on an electrically braked bicycle ergometer indicated that some shift in the MU recruitment and/or MU firing frequency may occur during the application of arterial occlusion causing local muscle hypoxia.
ABSTRACT
Various studies have reported on VO<SUB>2</SUB>max differences in men, with or without respect to distance run performances, and demonstrated that VO<SUB>2</SUB>max was the most important factor in endurance work capacity. This study was undertaken to reveal whether VO<SUB>2</SUB>max would still be the best determinant of endurance work capacity (or distance run performances), comparing it with AT parameters using the technique of correlational analyses. Twenty-seven distance runners, 16-26 years of age including an Olympic runner, underwent a multistage-incremental treadmill test for the assessment of submaximal and maximal work capacity. ATs were subjectively evaluated and determined as the point of breakaway of gas exchange criterion parameters according to Davis et al.'s method, and also referring to Wasserman et al.'s method.<BR>The mean VO<SUB>2</SUB>max was 4.518 <I>l</I>/mmn (70.1 ml/kg⋅BW/min, 78.1 ml/kg . LBM/min), whilst the mean AT appeared to be 3.444 <I>l</I>/mmn (52.8 ml/kg/min, 75.60% of VO<SUB>2</SUB>max) . These results are in good agreement with previous results reported by others. Interestingly, all distance performances (i.e., 1-mile, 2-mile, and 3-mile) correlated highest with AT (ml/kg/min), secondly with exhaustion time, and thirdly with either VO<SUB>2</SUB>max or another AT parameter. AT (ml/kg/min) alone accounted for approximately 510, 73%, and 80% of the variance in the 1-mile, 2-mile, and 3-mile performances, respectively.<BR>Since absolute VO<SUB>2</SUB>max is known to be a function of body size (e.g., body weight), an attempt was made to evaluate the relationships between the metabolic parameters and the distance performances through partial correlations holding the influence of body weight or LBM statistically constant. As a result, the correlation of VO<SUB>2</SUB>max (<I>1</I>/mm) with the 3-mile performance increased considerably to r<SUB>p</SUB>=-0.781 ; however, the degree of the relationship was not greater than the zero-order correlation (r=-0.896) obtained between AT (ml/kg/min) and the performance. Furthermore, when entered into a forward selection multiple regression with the 3-mile performance as the dependent variable, AT (<I>l</I>/min) accounted for only an additional 0.8% of the variance. VO<SUB>2</SUB>max (<I>l</I>/min), true % 02, % body fat body weight, VO<SUB>2</SUB>max (ml/kg/min), and vital capacity also accounted for only an additional 0.1%, 0.4%, 0.5%, 0.8%, 1.8%, and 1.8% of the variance, respectively. These data indicate that, considering the sample studied and limitations within this study, AT (ml/kg/min) could be the most significant determinant of the 3-mile run performance and, though to a lesser extent, the 2-mil eand 1-mile run performances.