ABSTRACT
The engaging>30 minutes of physical activity (PA) at 4-6 METs has been recommended for the prevention of cardiovascular disease. We determined whether relatively low intensity (i. e., 3-5 METs) PA inhibits the age-related central arterial stiffening, a risk of cardiovascular disease. In the cross-sectional study, the association between carotid arterial properties (via ultrasound system) and daily PA (via electric accelerometer) were studied in 172 normotensive people (41-82 yrs). People engaging>30 min/day of PA corresponding to 3-5 METs had a significantly lower beta-stiffness index than sedentary peers after adjusting for covariates (i. e., age and PA time at more than 6 METs). In the interventional study, beta-stiffness index of nine normotensive postmenopausal women was significantly decreased after the 12-week aerobic training (cycling at 80% of ventiratory threshold, ≈4 METs, 30 min/day, 5 days/week). These results suggest that the increase in daily PA at 3-5 METs inhibits the age-related carotid arterial stiffening.
ABSTRACT
The purpose of this study was to evaluate the association between subjective usefulness of pedometer and step count, exercise adherence, and the possibility of a pedometer helping exercise adherence.<BR>The subjects were 106 community-dwelling citizens (mean age±SD, 66±5) who were put on an individual exercise program in addition to walking. The targeted step count was 8000 steps/day. Every subject wore a pedometer that registers 7 days of physical activity.<BR>The rate of adherence was 98.1%, and about 73% of subjects answered that using a pedometer is useful for physical activity. There was no difference in exercise habit at baseline between subjects answering useful or not useful.<BR>Only in the case of females, was step count and prevalence of targeted 8000 steps significantly higher in the group who felt a pedometer was useful than in the group who didn't feel it useful. However, in the group of males who felt the usefulness of a pedometer, step count significantly increased during the 3 months. In addition, the females who reached their targeted step count performed better in the 10 m hurdle walk and 6 min walk than those who could not reach the targeted step count.<BR>The awareness of self-health wellness, without the anxiety of physical fitness and adherence to exercise was higher in the subjects who felt a pedometer was useful than in the subjects who didn't.<BR>The subjects who felt a pedometer was useful achieved their targeted number of steps and increased walking ability and tended to adhere better to physical activity.<BR>It is suggested that a pedometer motivates adherence to physical activity and is useful for helping exercise adherence in the future. However, we need a randomized control trial for determining the relationship between exercise adherence and using a pedometer.
ABSTRACT
Central arterial distensibility decreases with age-related changes in the arterial wall, and as a result, systolic blood pressure and/or pulse pressure (difference of systolic pressure and diastolic pressure) may increase in the elderly. Systolic hypertension and increased pulse pressure are known to be independent risk factors of cardiovascular and cerebrovascular diseases. Decreased distensibility of the central arteries may also cause the deterioration of circulatory function and physical ability in the elderly. Several studies have shown that central arterial distensibility is increased in athletes, and that daily physical activity is positively related to central arterial distensi bility in not only young but also elderly people. It has also been shown that relatively short-term and low-intensity exercise training could improve central arterial distensibility even in the elderly. Thus, physical exercise may have an effect on retarding age-related changes of the central arteries. To establish higher quality of life by preventing cardiovascular and cerebrovascular diseases and by improving circulatory function and physical ability in the elderly, further studies are needed to investigate the detailed mechanism and the appropriate amount and or intensity of exercise in improving central arterial distensibility.
ABSTRACT
The purpose of this research was to study the effects of exercise program participation on the personal factors of exercise adherence promotion in the middle-aged and elderly by comparing a group and individual exercise program. The personal factors for promoting exercise adherence, the four domains (i, e. initiative attitude, achievement satisfaction, self-recognition, and intrinsic motivation), were hypothesized. Two groups of middle-aged and elderly subjects, who volunteered to participate in different 6-month exercise programs, were examined. Group 1, 33 subjects (aged 67.7 ±4.3 years : mean±SD), participated in a program consisting of an individual exercise program (combination of endurance and resistance exercise, e. g. cycling exercise, dumbbell and machine exercise, once a week) and group exercise program (e, g. dance and ball game, once a week) . Group 2, 27 subjects (aged 65.2±4.Ovears), participated in the same individual exercise program twice a week. After the 6-month exercise program, significant improvements in group 1 were found in the selfassessment of activity score of the initiative attitude domain, the achievement satisfaction score including enjoyment, achievement and satisfaction, and the self-recognition score representing competence. In group 2, the mastery score in the intrinsic motivation domain was reduced, and the curiosity score in the same domain and the achievement score in the achievement satisfaction domain tended to decrease. These results show that a group program might have a more significant effect on the personal factors hypothesized to promote exercise adherence in this study. Hut there should be follow-up study on the subjects to determine the effectiveness of the program over the long term.
ABSTRACT
The purpose of this study was to confirm the causal effect model of strength on walking ability development as a result of exercise participation among elderly people in a community, utilizing the latent curve model (LCM) in structural equation modeling (SEM) . Twenty-six male and 57 female subjects, 83 in total, aged 67.8±5.7, 63.9±7.1 and 65.1±6.9 in a pooled sample participated in the exercise program which lasted for two years. Grip strength and sit-ups used in the Japan Fitness Test were measured for muscular strength, 10-m hurdle walk and 6-min walk for walking ability, and the fitness test score for physical ability. The data analysis procedures were as follows : a) analysis of test-retest reliability and construct validity of measurement items, b) analysis of causal structure model of aging, muscular strength and walking ability, c) analysis of variance for repeated measurement of walking performance by sex, age and year, d) analysis of LCM for walking performance development. The highest goodness-of-fit indices of SEM were obtained in the LCM of 10-m hurdle walk performance development (GFI=0.989, AGFI=0.920, CFI=0.998, RMSEA=0.038) . The path coefficient of sit-ups at pre-test effect on the intercept of 10-m hurdle walk performance development was significant (<I>p</I><0.05) . The path coefficients of age to intercept and slope of 10-m hurdle walk development were also significant (<I>p</I><0.05) . It was concluded that walking ability development through participation in exercise age and strength level was more effective for maintaining walking ability in older age.
ABSTRACT
Arterial compliance progressively decreases with aging. This aging-induced reduction of arterial compliance causes an increase of systolic blood pressure (SBP), whereas regular exercise increases arterial compliance. We hypothesized that an increase in daily physical activity (DPA) produces a beneficial effect on systemic arterial compliance (SAC ; an index of central arterial compliance) and this phenomenon could decrease SBP in the elderly. We investigated the relationship among DPA, SAC, SBP, diastolic blood pressure (DBP), and some other risk factors for cardiovascular and/or cerebrovascular events (total cholesterol, HDL-cholesterol, and HOMA-R) cross-sectionally in 127 elderly persons (42 male, 85 female : aged 74±4 years) . The DPA was estimated by expended calories using an accelerometer. The SAC was calculated from a finger pulse pressure waveform recorded by using PORTAPRES ; and stroke volume obtained from the same pressure waveform based on the volume-clump method. The analyses demonstrated that SBP was directly and decreasingly affected by SAC, and that DPA had an increasing effect on SAC. Furthermore, SBP was directly and increasingly affected by DBP, and DBP was directly and decreasingly affected by both SAC and DPA. Therefore, it is considered that DPA may have suppressive effects on the rise of SBP through the indirect effects of changing SAC and DBP. These findings suggest that an increase in DPA could improve the age-induced reduction of arterial compliance and rise of SBP in elderly humans.
ABSTRACT
The purpose of this study was to confirm the reliability and validity of a physical fitness questionnaire (PFQ) with self-rating for elderly people applying structural equation modeling (SEM) . As subjects, 105 community-dwelling older men and women aged 67.1±6.1 years participated in the study to measure 13 PFQ items and 13 performance tests. The data analysis procedures were as follows : a) testing reliability of PFQ ; b) testing of construct validity of PFQ using exploratory factor analysis (EFA) and confirmatory factor analysis (CFA) ; c) testing of criterion-related validity of PFQ to the performance tests using SEM ; d) testing of correlations of the PFQ to walking ability using SEM. Cronbaeh's alpha coefficient for consistency reliability of the PFQ was .83. Four common factors of muscle strength-power, endurance, coordination, and flexibility were extracted in EFA. The high and enough goodness of fit indices were obtained in the confirmatory factor structure model, and in each sub-domain of criterion-related validity to performance tests and correlation to walking ability models. The criterion-related validity coefficient of muscle strength and power was .77, followed by .66 for endurance, .59 for coordination and .82 for flexibility. The correlation coefficient of muscle strength and power to walking ability was -.51, followed by -.58 for coordination, - .43 for endurance and - . 28 for flexibility. These results indicated that the PFQ consisting of 13 items and 4 sub-domains satisfied reliability and construct validity although criterion related validity to performance tests was insufficient. It was concluded that the PFQ is of useful for physical fitness checking of elderly people.
ABSTRACT
The purpose of this study was to confirm the causal structure model of muscle, motor and living functions utilizing structural equation modeling (SEM) . As subjects, 103 community-dwelling older men and women, aged 65.7±6.9years of age, participated in the study to measure muscle cross-sectional area, maximum voluntary contractions, muscle power, 4 physical performance tests, and 16 questionnaires regarding ability of activities of daily living. The causal structure model of muscle, motor and living functions was hypothesized to be a hierarchical causal structure. The causal structure model of muscle function was hypothesized to be a hierarchical causal structure consisting of 3 sub-domains of muscle mass, muscle strength, and muscle power. Data analysis procedures were as follows : a) testing of construct validity of muscle function variables using confirmatory factor analysis (CFA) in SEM ; b) testing of causal structure using SEM ; c) testing of factor invariance using multi-group analysis for gender. The highest goodness of fit indices was obtained in the causal structure model of muscle, motor and living functions (NFI= .928, CFI= .978, RMSEA =.061) . The causal coefficient of muscle function to motor function was .98 (<I>p</I><.05), followed by.34 for motor function to living function. From the results of multi-group analysis, the measurement invariance model indicated the highest goodness of fit indices (TLI=.968, CFI .977) . It was concluded that the hierarchical causal relation was among muscle, motor and living functions, and in which muscle function was consisted of 3 sub-domains.
ABSTRACT
Resistance exercise in the elderly and patients with a cardiovascular disorder has been thought to have a high cardiovascular risk, because it has the tendency to cause an excessive rise in blood pressure and induce serious arrhythmia. But recently, resistance exercise has been introduced into physical therapy because the safety of such exercise has been confirmed in subjects without a cardiovascular disorder.<BR>The purpose of this study was to investigate the safety of lower extremity resistance exercise in middle-aged or elderly subjects with hypertension and receiving medical treatment (n=24), and those without hypertension (n=40), by measuring cardiovascular response during resistance exercise of different loads (40% and 60% 1 RM), and usefulness of respiratory guidance during such exercise.<BR>As a result, there was no difference in diastolic blood pressure between those with and without hypertension ; but systolic blood pressure and rate pressure product both at rest and during exercise were significantly greater in patients with hypertension. However, neither group showed symptoms of angina, ischemic signs in ECG, or serious arrhythmia ; and there was no difference in the frequency of excessive rise in blood pressure between the groups (2 subjects with hypertension and 1 subject without hypertension) . Blood pressure during exercise was significantly lowered by respiratory guidance.<BR>These results show that it is important to measure blood pressure during exercise before resistance exercise training regardless of the presence of hypertension, although an excessive rise in blood pressure occurred in only a few subjects. Furthermore, it is important to exhale slowly and not hold one's breath during exercise.
ABSTRACT
The effect of daily physical activity on oxidative stress is still an unknown issue, especially in middle-aged and elderly individuals. In this study, we examined the relationships of oxidative stress and antioxidant capacity with daily physical activity, taking into consideration the dietary antioxidant vitamin intake (vitamin B<SUB>2</SUB>, C and E) of middle-aged and elderly people (66.0±7.0 years, n= 21; 10 males and 11 females, including 5 male trained runners) . Daily physical activity was measured using both a calorie counter and a questionnaire over a period of two weeks. The plasma concentration of thiobarbituric acid reactive substance ( [TBARS] ) and both oxidized and reduced glutathione concentrations ( [GSSG] and [GSH] ) in whole blood were determined in blood samples obtained at rest and immediately after two periods of acute exercise: maximal cycle ergometric exercise and steady state cycle exercise at 80% of ventilatory threshold (VT) for 30 minutes. At a given statistically controlled dietary antioxidant vitamin intake level (vitamin B<SUB>2</SUB>, C and E), the amount of daily physical activity was associated with neither [TBARS], [GSH] and the ratio of [GSSG] / [GSH] at rest, nor changes in levels of these substances after both exercise tests. These data suggest that the amount of daily physical activity may have little influence on oxidative stress or antioxidant capacity at rest and after acute cycle ergometric exercise. Further investigation would be necessary to clarify how much volume or intensity of physical activity induces increased oxidative stress, from the aspect of habitual physical training and nutrition.
ABSTRACT
The effects of endurance training and detraining on cardiac autonomic nervous system activity were studied by using the power spectral analysis of heart rate (HR) variability. Twenty-one sedentary male subjects were trained for 8 weeks using cycle ergometer exercise [70% of maximal oxygen uptake (VO<SUB>2</SUB>max), 60 min, 3.4 times/wk] . Resting HR for 5 min was recorded before the training, after the 8-week training period, and after the 2-week and 4-week detraining period. The indices of cardiac parasympathetic and sympathetic nervous system activity were determined by Mem-Calc method, as the high frequency power (HF : 0.15-0.50 Hz) and the ratio of the low frequency power (LF : 0.04-0.15 Hz) to the HF (LF/HF), respectively. The VO<SUB>2</SUB>max after the training and 4 weeks detraining period were significantly higher than the initial value (before training : 41 ± 1 ml/kg/min ; after training: 48±2, <I>P</I><0.0001; after detraining: 46±2, <I>P</I><0.001) . The HF was significantly in-creased by the training (<I>P</I><0.05), and maintained the increased level for the 2-week detraining period (before training : 6.4±0.3 In ms<SUP>2</SUP>; after training: 7.0±0.2, <I>P</I><0.01; after 2-week detrain-ing: 7.0±0.2, <I>P</I><0.05) . The increase in the HF, however, disappeared after the 4-week detraining period (6.8±0.31n ms<SUP>2</SUP>) . The LF/HF did not show any significant changes during the training and detraining period. These results suggest that an endurance exercise with moderate intensity enhan-ces cardiac parasympathetic nervous system activity, but not cardiac sympathetic nervous system activity. The enhanced cardiac parasympathetic nervous system activity, however, may regress rapidly during detraining period.
ABSTRACT
It has been shown that the time constant of heart rate decline for the first 30 sec (T<SUB>30</SUB>) after exercise, at an intensity lower than the ventilatory threshold (VT), can serve as a specific index to assess post-exercise vagal reactivation. The purpose of this study was to validate the use of a simpler alternative index, i. e. %Δ HR<SUB>30</SUB> (the ratio of heart rate decrement for the first 30 sec after exercise) for the evaluation of parasympathetic nervous reactivation, and to examine whether it would be a useful index in the conditioning of athletes. Eighteen college students performed 4 minutes cycle ergometer exercise routines at intensities of 40%, 80%, and 120% VT to compare the %Δ HR<SUB>30</SUB> and the T<SUB>30</SUB>. In addition, the %Δ HR<SUB>30</SUB> was obtained by a field test (4 minutes jogging) in 15 college middle and long distance runners, every morning during summer camp training to assess the state of athletic conditioning. The %Δ HR<SUB>30</SUB> at 80% VT was similar to the value at 40% VT, but significantly different from the value at 120% VT, as was the T<SUB>30</SUB> at 80% VT.<BR>The %Δ HR<SUB>30</SUB> significantly correlated with the T<SUB>30</SUB> and VO<SUB>2</SUB>max. During the camp, the %Δ HR<SUB>30</SUB> was higher on mornings following light training days than on mornings following hard training days. These results suggest that the %Δ HR<SUB>30</SUB>, at an exercise intensity lower than the VT, could be a simple and useful index to evaluate post-exercise parasympathetic nervous reactivation in the conditioning of athletes.
ABSTRACT
We have been proceeding with studies on the effects of water immersion on autonomic nerve activity using the power spectral analysis of heart rate variability. The results obtained so far suggest that cardiac parasympathetic nerve activity is enhanced and sympathetic nerve activity is suppressed during immersion at temperatures between 25°C and 34°C and that parasympathetic nerve activity is suppressed and sympathetic nerve activity is enhanced during immersion at temperatures around 38°C. However, water immersion affects the respiration rate and tidal volume, and though the change in the respiration rate does not affect the real cardiac autonomic nerve activity, it affects the index of autonomic nerve activity as assessed by the power spectral analysis of heart rate variability. Therefore, this study examined the changes in cardiac autonomic nerve activity during water immersion with the tidal volume measured and its changes considered while controlling the respiration to a certain level. Eight healthy young males (ages: 19 to 28) sat calmly for 20 minutes before immersion and then soaked in water at the subaxillary level in sitting position for 15 minutes while controlling their respiration rate to 15cycles/min. Autonomic nerve activity was estimated by the power spectral analysis of the heart rate together with the Fast Fourier Transformation. Integral values of power were obtained in the high frequency (HF; 0.15 to 0.50Hz) and low frequency (LF; 0.04 to 0.15Hz) component areas. HF was used as the index of cardiac parasympathetic nerve activity, and the ratio of LF to HF (LF/HF), as the index of cardiac sympathetic nerve activity. During immersion at 34°C, HF increased significantly and the heart rate and LF/HF decreased slightly though not at a statistically significant level. During immersion at 27°C, HF increased significantly and the heart rate and LF/HF decreased significantly. During immersion at 38°C, the heart rate increased significantly while HF decreased and LF/HF varied slightly with no statistical significance. The tidal volume increased significantly during immersion at 27°C and 34°C, and it increased during immersion at 38°C though it was not statistically significant.<br>These results suggest that cardiac parasympathetic nerve activity is enhanced while sympathetic nerve activity is suppressed during immersion at 27°C, because the remarkable increase in HF that occurred during immersion cannot be accounted for by the increase in the tidal volume per breathing cycle alone. However, it is possible that the increase in the tidal volume enhanced the increase in HF. It was suggested, however, that autonomic nerve activities did not change significantly during water immersion at 38°C though there is possibility that the changes in HF were underestimated due to the increase in the tidal volume.
ABSTRACT
The authors hypothesized that habitual physical exercise and aortic distensibility would be the major factors which influence systolic blood pressure. This study was designed to analyze the relationships among systolic blood pressure (SBP) and parameters determined at medical checks, including age, diastolic blood pressure (DBP), aortic pulse wave velocity (APWV) index (APWVI : APWV standardized by the diastolic blood pressure), plasma lipid profiles (IC, TG), plasma glucose during an oral glucose tolerance test (2 h-OGTT), percentage body fat (%Fat), cigarette smoking habit (Cigarettes), alcohol consumption (Alcohol), and physical activity index (PAI) using a questionnaire, in 678 males aged 30 to 69 years, who visited a hospital for a thorough medical check-up. For analysis of factorial structure in the subjects, principal factor analysis was applied to the correlation matrix which was calculated with 12 variables. Correlational analysis and path analysis were applied to confirm the hypothetical model. The results demonstrated that DBP and APWVI were the major factors which significantly affected the SBP. The PAI was significantly and inversely correlated not only with the APWVI, but also with %Fat, which was significantly and positively correlated with the DBP. In conclusion, aortic wall stiffness may be an independent factor in the manifestation of systolic hypertension, and habitual physical exercise may decrease the SBP through direct reduction of aortic wall stiffness and indirectly decreasing the DBP.
ABSTRACT
It is generally accepted that visually impaired individuals generally have a low aerobic capacity, which may be partly attributed to a lack of physical activity, and have hypothesized that their response to exercise may differ from that of normal-sighted people. In this study, we investigated the effect of exercise on local immunity in the oral cavity in 24 visually impaired males (n=8 ; totally blind group, n=16 ; partially sighted group) and 8 normal-sighted males. The subjects performed submaximal graded bicycle ergometer exercise to an intensity of 75% heart rate max for 12 min. Before and immediately after exercise, we collected timed saliva samples and measured secretory immunoglobulin A (sIgA) .<BR>The totally blind group had lower levels of aerobic capacity and a lower sIgA secretion rate compared to the partially sighted and sighted groups. Immediately after exercise, the sIgA secretion rate tended to increase in the totally blind group.<BR>It is suggested that the exercise-induced response of local immunity in the totally blind group differed from that in the other groups.
ABSTRACT
Although it has been established that exercise is useful for health promotion, physical exercise may induce oxidative stress in humans. Our previous study showed that the concentration of plasma protein-bound sulfhydryl groups (p-SHs) was significantly decreased after strenuous exercise, i. e. full-marathon running and participation in an athletic training camp. Reactive oxygen species may cause oxidation of plasma proteins <I>in vitro</I>. To study whether moderate exercise for health promotion, e. g. jogging or walking, induces oxidative stress in human circulating blood, the authors examined the change in plasma p-SHs concentration following ergometric exercise at moderate intensity and of relatively short duration {Exercise 1: 80% ventilatory threshold (VT), 100% VT, and 110% VT; 30 min, Exercise 2 : 90% VT; 120 min} in 8 (23-28 yr; Exercise 1) and 6 males (23-28 yr; Exercise 2) respectively. The plasma p-SHs concentration did not changed significantly after Exercise 1 or 2. The data indicated that the exercise did not cause significant modification of plasma proteins, suggesting that it did not induce significant oxidative stress in the circulating blood.
ABSTRACT
The purpose of this study was to assess an alteration of cardiac autonomic nerve activity during water immersion. Ten healthy young males (age : 21-28 yr.) were immersed in water at the temperatures of 25°C, 30°C and 34°C. Subjects sat calmly for 20 minutes in sitting position before water immersion, and then were immersed in water at subaxillary level in sitting position for 15 minutes, performing controlled breathing (15 cycle/min.) . Electrocardiograms were recorded continuously. Autonomic nerve activity was estimated with the analysis of power spectral by using the Fast Fourier Transformation (FFT) . High (HF ; 0.15-0.50 Hz) and low (LF ; 0.04-0.15 Hz) frequency areas and the ratio of LF to HF (LF/HF) were calculated as the indices of cardiac parasympathetic nerve activity, sympathetic nerve activity with parasympathetic modulation, and sympathetic nerve activity, respectively. During the water immersion at 25°C, 30°C and 34°C, HF was significantly increased, while the heart rate and LF/HF were significantly decreased. There were no statistically significant differences among both of HF and LF/HF during the immersion at 25°C, 30°C and 34°C, although the rate of change in HF at the temperature of 25°C appeared to be prominent compared to those at 30°C and 34°C and some subjects showed an exaggerated change in HF immediately after immersion. These results suggest that cardiac parasympathetic nerve activity is enhanced and cardiac sympathetic nerve activity is suppressed during a short time water immersion at the thermo-neutral temperature (34°C) and the temperatures of 25°C and 30°C, which are the usual temperatures found in indoor pools.
ABSTRACT
This study was conducted to assess the effects of bathing in still water and in flowing water on the heart rate variability. Eight healthy young males (age 20 to 28) bathed in still water at temperatures of 34°C, 38°C, and 41°C for 20 minutes each. The other eight healthy young males (age 22 to 28) bathed in flowing water at a temperature of 36°C for 30 minutes. Electrocardiograms were recorded before, during, and after the bathing. Subjects sat still for 20 minutes before bathing, and then bathed in water to the axilla in a sitting position. Subjects breathed freely during the experiment. Heart rate variability was estimated with the power spectral analysis using FFT. The power densities in the high frequency (0.15 to 0.50Hz) and low frequency (0.04 to 0.15Hz) areas as obtained from this frequency analysis (HF and LF) as well as the ratio of LF/HF were calculated, and HF was used as index of cardiac parasympathetic activity, LF as index of sympathetic activity with parasympathetic modulation, and LF/HF as index of sympathetic activity.<br>During bathing in still water at 34°C and 36°C, no significant change from the value before the bathing was found in heart rate, HF, LF, or LF/HF. HF and LF significantly decreased during the bathing in still water at 38°C and 41°C, LF/HF significantly increased during the bathing in still water at 38°C, During the bathing in still water at 41°C, we could not calculate LF/HF for many subjects because HF disappeared. During the bathing in water flowing at a moderate speed (1.0m/sec), LF/HF increased significantly. During the bathing in water flowing at a high speed (2.0m/sec), heart rate and LF/HF increased significantly while LF decreased significantly.<br>These results suggest that parasympathetic nervous activities are suppressed and sympathetic nervous activities are enhanced during bathing in still water at temperatures higher than the neutral temperature (34°C), and sympathetic nervous activity is enhanced during the bathing in flowing water at 36°C, However, the effects of respiration rate and tidal-volume on HF, and the validity of the HR variabilities as an index of autonomic nervous activities should be examined in further detail.
ABSTRACT
A study was carried out to examine the effects of water replacement on cardiovascular function during kendo practice in a hot environment. Five male college kendoists performed moderately severe 30-min kendo practice at a WBGT index of about 27°C with and without water intake. For water replacement, the subjects ingested 700 ml water (500 ml before exercise and 200 ml at 15 min after the start of exercise) . Under both conditions, body weight was decreased significantly, and hematocrit and serum total protein concentration were increased significantly after the exercise. With water replacement, the body weight loss induced by the exercise was similar to that under water deprivation. However, the decrease in body weight from the basal body weight, i. e. body weight measured before water intake, was significantly less with water replacement than under water deprivation. There were no significant differences in the percentage increases of hematocrit and serum total protein concentration between the two conditions, although the percentage change in plasma vasopressin concentration was significantly lower with water replacement than without. In the subjects deprived of water, the left ventricular end-diastolic dimension and left atrial dimension were significantly reduced after the exercise, and stroke volume, ejection fraction, and fractional shortening were also decreased significantly. The ratio of left ventricular end-systolic wall stress to left ventricular end-systolic volume index was increased significantly after the exercise without water intake. With water replacement, however, the percentage decreases in cardiac dimensions, stroke volume, ejection fraction, and fractional shortening were significantly lower than those under water deprivation. There was no significant change in the ratio of left ventricular end-systolic wall stress to left ventricular end-systolic volume index before and after the exercise with water intake. It is suggested that 700 ml water replacement before and during kendo exercise in a hot environment prevents depletion of stroke volume and deterioration of cardiovascular function, although it might not improve significantly the plasma volume loss after exercise.
ABSTRACT
To study the effects of prolonged kendo practice in a hot environment on cardiovascular function, certain hemodynamic parameters were measured in 5 male college kendo fencers before and after 1 hour of kendo practice performed at a dry bulb temperature of 30.4t and wet bulb temperature of 26.2°C After kendo practice, body weight was significantly decreased and both hematocrit and blood viscosity were significantly increased. The left ventricular end-diastolic dimension and the left atrial dimension, measured by echocardiography, were significantly reduced after kendo practice, and stroke volume, ejection fraction, and fractional shortening were also significantly decreased after practice. The same fencers were subjected to lower body negative pressure testing designed to reduce the left ventricular end-diastolic dimension to the same degree as kendo practice, and comparable decreases in stroke volume, ejection fraction, and fractional shortening were observed. The ratio of end-systolic wall stress to end-systolic volume index was significantly increased during both kendo practice and lower body negative pressure testing. We conclude that prolonged kendo practice in a hot environment impairs cardiac pump function by reducing preload in parallel with the decrease in venous return, that myocardial contractility may not deteriorate despite marked hemoconcentration, and that fluid intake during practice may prevent deterioration of cardiovascular function.