A study was designed to examine the effects of exercise intensity on renal clearance parameters. Five healthy male subjects underwent exercise tests on an bicycle ergometer at 4 different work loads for 15 min. The indicators of exercise intensity employed were the percentage of maximal oxygen uptake (%VO2max), heart rate (HR) and blood lactate level (La) . As parameters of renal clearance, para-aminohippurate clearance (CPAH), thiosulfate clearance (Cthio) and creatinine clearance (Ccr) were measured by the continuous infusion technique during the exercise. 1) The renal clearance parameters during exercise decreased linearly as the exercise intensity increased. The percentage of maximal oxygen uptake at the onset of the decreases in %CPAH, %Cchiu and %Ccr were 36, 45 and 47%VO2max, respectively. 2) Among the indicators of exercise intensity, the decrease in La showed the closest correlation with renal clearance during the exercise. 3) The renal plasma flow, which was measured as CPAH, began to decrease linearly at a significantly lower exercise intensity than the glomerular filtration rate, which was measured as both Cthio and Ccr. The above results suggest that renal clearance parameters begin to decrease at the threshold as exercise intensity increases.
Male mice of dd-strain, at 4 weeks of age were used in the present study. The materials were divided into four groups; namely, mildly, moderately, severely trained and untrained. The treadmill exercise program for mildly, moderately and severely trained groups consisted of running at speeds of 6 m/min, 10m/min and running up a 10% grade at a speed of 12m/min for 10 min 5 times a week, respectively. The collagen content of the skin was measured by means of concentration of hydroxyproline. Moreover, the proportion of neutral salt-soluble (NSC), acetic acid-soluble (ASC) and insoluble collagen (ISC) in the skin was isolated. We attempted to study about the effects of physical activity on the metabolism of collagen by aging. Hydroxyproline concentration of the skin in untrained group increased rapidly until 6 weeks of age. Maximum hydroxyproline concentration was observed at 7 weeks of age in untrianed group. In three trained groups, maximum hydroxyproline concentration was observed at 9 weeks of age. The collagen content of the skin in the three groups was higher than that in untrained group at 9 and 11 weeks of age. The proportion of NSC, ASC and ISC of the skin varied with age in four groups. In the untrained group, the proportion of ISC increased with age and was recognized to reach 81.9% at 15 weeks of age. The proportion of NSC and ASC in both the moderately and severely trained groups indicated approximately 20% increase compared with that in the untrained group. This fact suggests that the degree of maturation of collagen is influenced by physical activity, especially, moderately and severely training. The authors conclude that continuous exercise training control the formation of intramolecular and intermolecular cross-links in skin collagen.
Information on daily physical activity is essential for determining daily nutritional demands and devising physical conditioning programs. In order to obtain reliable information on daily physical activity, it is necessary to record the activity in some way. Up to now, however, such data have been collected using retrospective questionnaires and observation, and by measurement of heart rate over extensive periods. These methods are too cumbersome and expensive. The purpose of the present study was to develop a new device for recording physical activity in the form of an actogram. A pedometer was used to record the physical activity, and a microswitch was set inside the pedometer to convert the pedometer count into an electric signal, since it is advantageous to process the data by computer. The pedometer count was recorded in the IC memory of a computer with a 32-kbyte. The memorized pedometer count was fed into the personal computer through an interface, and after processing it was displayed as an actogram representing the activity pattern and the amount of physical activity. The new device developed in this study could serve as a practical tool for recording the quantity and time course of physical activity during daily life, since it is small (110mm×70 mm×30 mm) and light (170g), less expensive and also convenient to handle.
A study was conducted to examine the feasibility and validity of using integrated electromyographic signals (IEMG) for determination of anaerobic threshold (AT) in the elderly. Twentynine healthy elderly subjects (aged 67.6±7.7 yr) and twelve young males (aged 23.2±7.9 yr) performed ramp cycle exercise to exhaustion, increasing at a rate of 12.5 W/min for the elderly group and 25.0 W/min for the young group, following 3 min of exercise at zero work load. Myoelectrical signals were measured continuously from the vastus lateralis muscle, and values in terms of IEMG were computed every 10s throughout the test with AID conversion at 500 Hz. For the criterion of IEMG threshold, the breakpoint in the relationship between power output and IEMG was determined by two-segmental linear regression. VT was defined as the VO2 at the onset of a nonlinear increase in VE and/or a sustained rise in VE/VO2 without a rise in VE/VCO2. It was found that the value of VO2 in terms of IEMGT was similar to VT in both groups, 16.3 and 18.1 ml/kg/min for the elderly group and 33.5 and 36.3 ml/kg/min for the young group, respectively. Furthermore, IEMGT was correlated significantly (p<0.001) with VT in both groups (r=0.871 for the elderly group and r=0.925 for the young group) . It is concluded that the IEMGT method for determination of AT in the elderly is simple and useful.
Nutritional profiles in middle-aged trained and untrained women were compared both before and after menopause. Subjects were assigned to one of four groups : (1) pre-menopausal trained (Pre-T: n=14, aged 43±5 years, running distance 56±27 km/week, Vo2max 49±4ml/ kg/min, mean±SD), (2) pre-menopausal untrained (Pre-UT: n=25, 42±5 years, 34±5 ml/kg/ min), (3) post-menopausal trained (Post-T: n=19, 53±3 years, 49±17 km/week, 42±6 ml/ kg/min), (4) post-menopausal untrained (Post-UT: n=26, 54±3 years, 31±3 ml/kg/min) . There were no significant differences in hematocrit (range 38.7 to 39.3%), hemoglobin (12.8 to 13.1 g/dl) and total protein (6.9 to 7.1 g/dl) among the four groups. Serum iron concentrations in the post-menopausal women (Post-T: 97±30μg/dl, Post-UT: 106±29μg/dl) were relatively higher than in the pre-menopausals (Pre-T: 85±35 pg/dl, Pre-UT: 78±33 pg/dl) . Mean total iron binding capacity in Post-UT (326 pg/dl) was lower than other groups (352 to 361 pg/dl) . Higher serum ferritin levels were observed in the post-menopausal women (Post-T : 35.8±27.5 ng/ml, Post-UT : 60.4±47.1 ng/ml) than the pre-menopausals (Pre-T: 18.3±13.1 ng/ml, Pre-UT: 16.6±10.7ng/ml) . Intake levels of the four groups with regard to the major nutrients were sufficient as compared with the recommended dietary allowance appropriate for age, sex and physical activity level. Intakes of calcium, iron and vitamins B1, B2 and niacin were higher in the trained groups than in the untrained. Regularly performed endurance exercise resulted in higher protein and iron intakes associated with higher energy intakes both before and after menopause. These results suggest that nutritional status of middle-aged women who regularly perform vigorous endurance running could be adequate for maintaining their health in a good state.
An investigation was conducted to clarify both the effect of water polo training on bone mass and the effect of training-induced menstrual disorders on bone. The subjects were 12 female college water polo players and 7 age-matched sedentary college women as a control group. Menstrual condition was evaluated by 12 montes of basal body temperature measurement. Seven of the water polo players were eumenorrheic, and five had training-dependent (reversible) menstrual disorders (two with amenorrhea and three with cycle disturbances) . Bone mineral measurement revealed differences between the water polo players and the sedentary women. The eumenorrheic water polo players had a higher bone mineral density (BMD) in the lumbar spine and total body skeleton than the sedentary control group, being 11.2% and 11.3% higher, respectively. Effects of menstrual disorders (including cycle disturbance) were clear in the water polo players. The BMD of water polo players with menstrual disorders was 9.8% and 9.6% lower in the total body and lumbar spine that of eumenorrheic water polo players. Hormonal examinations revealed a lower serum estradiol level in water polo players with menstrual disordsers in comparison with eumenorrheic water polo playes. Serum estradiol level showed a positive correlation with both total body BMD (r=0, 78, p<0.01) and lumbar spine BMD (r=0.71, p<0.01) .
A study was undertaken to evaluate the effect of aerobic training on lactate oxidative capacity during aerobic exercise using [U-14C] lactate. Male ddY mice were trained by means of treadmill running 5 days a week for 6 weeks. [U-14C] lactate was injected after the first 5 min of running at a speed of 30m⋅min-1. The mice then continued to run for another 25 min at the same speed. Expired gas was collected to estimate the amount of 14CO2 expired during the exercise. The amount of [14C] lactate expired as 14CO2 during the first 10 min after injection of [14C] lactate was significantly higher in the trained group (T) than in the control group (C) . The blood lactate concentration, and muscle lactate concentration in the soleus immediately after exercise were significantly lower in T than in C. The muscle glycogen and blood glucose concentrations were higher in T than in C. It is concluded that aerobic training in mice decreases the blood lactate concentration during exercise, and also enhances oxidative removal of lactate.
The present study was carried out to elucidete whether the accumulation of triglyceride (TG) in rat liver during fasting was stimulated by swimming. Male Wistar rats were divided into three groups; C: control, 24 F: 24 hour-fasted and 48 F: 48 hour-fasted. These animals were required to swim for 120 min. In rats with both 24F and 48F, the liver glycogen contents did not change during swimming. The level of TG in rat liver was higher in 24 F and 48 F rats than the control group, and the exercise significantly affected the liver TG in each group. There was significant correlation betweem the level of TG in rat liver and the plasma free fatty acid (FFA) concentration (r=0.681, p<0.01) . However, although plasma TG did not change during exercise in each group, the TG secretion rate (TGSR) of the 48 F group was significantly lower than that of the C and 24F groups (p<0.01) . These results provide evidence that exercise may result in the accumulation of TG in liver during fasting and suggest that the process not only depends on the surplus supply of FFA, but also inhibits very low density lipoprotein-TG secretion from liver.
Athletic women often exhibit menstrual disorders such as luteal insufficiency, oligomenorrhea and amenorrhea are often seen. It has been suggested that such disorders are related to prolactin release caused by physical activity. To investigate the mechanism by which the disorders are promoted, prolactin secretion was studied in 10 athletic women (5 with normal ovulatory periods, and 5 with short luteal periods) and 6 non-athletic controls. Blood samples were obtained during the early follicular phase of the menstrual cycle through an indwelling venous catheter at 15-minute intervals for 4 hours. The concentration of prolactin was measured by radioimmunoassay. The mean prolactin concentration in the athletic group was lower than that in the control group (p<0.001), and pulse frequency in the athletic group was higher than that of the control group (p<0.01) . Pulse amplitude in the athletic women with short luteal periods was higher than that of those with normal ovulation. Pulse duration in the athletic women with short luteal periods was significantly longer than that of those with normal ovulation (p<0.01) . These findings suggest that prolactin is one of the most important factors in menstrual disorders in athletic women.
A study was conducted to ascertain the relationship between oxygen uptake (Vo2) and vertical velocity using a pedal-stepping stair simulator. Ten healthy volunteers performed fbur kinds of graded exercise using a stair simulator (SS), whose pitches were set at 80, 100, and 120 beat⋅min-1, and also an electrically braked bicycle ergometer (BE) . Work rate on the SS was detemined on the basis of the vertical pedal velocity, in accord with the climbingvelocity for stairs. The incremental rate was set at 0.34 W⋅kg-1 every 3 min. Heart rate and Vo2 were measured during the final minute of every stage. Both heart rate and Vo2 during SS were significantly lower than those on BE at the same level of work intensity. Regression equations between Vo2 (ml⋅kg-1⋅min-1) and velocity (v: m⋅s-1) were as follows; pitch 80: Vo2=1.00×v+0.06 pitch 100: Vo2=0.88×v+1.58 pitch 120: Vo2=0.84×v+2.13 These equations give a lower value of Vo2 than the previous equation based on stair-climbingvelocity reported by the American College of Sports Medicine. Although the individual relationship between Vo2 and heart rate was closely linear, there was a significant effect ofexercise mode and stepping pitch. These results indicate that the work intensity of pedalstepping exercise with a stair simulator is overestimated if it is calculated based on theprevious equation for stair-climbing.
The effects of an arm lifting movement (ALM) on maximum vertical jumps with all but the ankle joints fixed (propelled only by plantar flexion) were studied in five subjects. ALM increased flight time, but did not alter maximum angular velocity of the ankle before takeoff. Holding 4kg dumbbells in their hands enhanced the effect of ALM on flight time. ALM increased the maximum force and the force at the onset of plantar flexion. Elbow angle recordings showed that both arms were accelerated before or around plantar flexion onset, and decelerated mainly after takeoff. In another series of experiments, we measured the vertical component of head and hand acceleration with accelerometers. ALM produced positive acceleration of the head after takeoff, which was related to negative acceleration of the hand. The results suggest that ALM increased flight time by enhancing plantar flexion torque under suppression of ankle angular velocity before takeoff. We discussed the relationship between this suppression and different acceleration between the arms and the body except the arms.