RELATIONSHIP BETWEEN BODY SURFACE COOLING AREA, COOLING CAPACITY, AND THERMOREGULATORY RESPONSES WEARING WATER PURFUSED SUITS DURING EXERCISE IN HUMANS / 体力科学

This study analyzed the effects of various body surface areas being cooled by water-perfused suits (WPS) on thermoregulatory response during exercise in a hot environment. Seven male subjects, dressed in clothing with low moisture permeability (rain coats) over WPS covering the whole body surface except for the face, hands, and feet, performed three sessions of 20-min cycling at low intensity (250w/m²) in a room maintained at 30℃ under six conditions of body surface cooling : whole body (WB), upper body (UB), lower body (LB), lower body except lower legs (LBEL), head and neck (HN), and no body cooling (NBC). The coolant temperature at the inlet was 20℃ for all conditions, and heat extraction (HE) was estimated by the difference between inlet and outlet water temperatures and water flow rate. Esophageal (Tes) and deep thigh temperatures (T-d.thigh) and heart rate (HR) during exercise were significantly (p＜0.01) higher for NBC and HN, and forearm skin blood flow (SkBF) and dehydration (DEH) were significantly (p＜0.01) lower for WB than for other conditions. There was a similar tendency concerning Tes and T-d.thigh among WB, LBEL, and LB ; however, T-d.thigh for UB was significantly (p＜0.01) higher than for WB, LBEL, and LB. In comparison with resting levels, the mean skin temperature (Tsk) and thermal sensation (TS) significantly (p＜0.01) increased for NBC and HN, and decreased for UB and WB, but remained constant for LBEL and LB during exercise. Under all conditions, increases in Tes (ΔTes) and T-d.thigh (ΔT-d.thigh) at the end of exercise were significantly (p＜0.01) increased when less than 40% of the body surface was cooled (Tsk : above 35.8℃, HE : less than 110W). Furthermore, ΔTes at the end of the exercise was related to ΔTsk×SkBF, while the slope of the regression line between those parameters was steeper when ΔTsk×SkBF values were negative, as opposed to positive values. These results suggest that during light exercise under different body surface cooling conditions : 1) UB leads to a high T-d.thigh while Tes, Tsk, and TS are as low as those for WB, 2) critical levels of body surface cooling area causing a decrease in core temperature elevation might exist, and 3) changes in blood circulation due to body cooling might be affecting temperature responses at the end of exercise.

CHANGES IN FINGER COLD-INDUCED VASODILATION BETWEEN SKI-AND PHYSICAL-TRAINING / 体力科学

The present study aimed to examine the change cold-induced vasodilation (CIVD) of finger between seven female alpine (AP group) and six female cross-country skiers (CC group) at different points in their training programs. The CIVD test was performed twice, once in spring period after ski-training, once in the summer period during physical-training.From the onset of ice-water immersion in each CIVD test, finger skin temperature in each group fell followed by an incline. Thereafter, finger skin temperature began to rise and fall in an attenuated fashion during ice-water immersion. The resistance index (RI) in summer (7.1±1.7) for AP group was significantly (P<0.01) higher than that in spring (4.6±1.1). However, that of CC group showed no difference between spring and summer.These results suggested that the physical training during summer period for AP group may influence on the improvement of CIVD.

Seasonal variation of trace element loss to sweat during exercise in males

<p><b>OBJECTIVE</b>To clarify the seasonal differences of the trace element excretion in sweat, the trace element concentration in sweat and their loss during exercise were compared between summer and winter.</p><p><b>METHODS</b>Sweat samples were collected from ten healthy adult males. Bicycle ergometer exercise was conducted by each subject at a heart rate of 140 beats/min for 1 hour, in summer and in winter. Sweat was collected by the arm bag method.</p><p><b>RESULTS</b>Concentrations of major (Na, K, Ca, and Mg) and trace elements (Zn, Cu, Fe, Ni, Mn, and Cr) in sweat tended to be lower in summer than in winter, and significantly lower concentrations of Mg (p<0.01), Na, Cu, and Mn (p<0.05) were found in summer. The sweat volume in summer (0.90 L) was 1.7-fold larger than that in winter (0.52 L) (p<0.01). The amount of loss of each element to sweat calculated from the concentrations in sweat and sweat volume showed no significant difference between summer and winter.</p><p><b>CONCLUSIONS</b>It is suggested that there was no significant difference in the amount of loss of trace elements in sweat due to exercise between summer and winter.</p>

Seasonal Variation of Trace Element Loss to Sweat during Exercise in Males

Objective: To clarify the seasonal differences of the trace element excretion in sweat, the trace element concentrations in sweat and their loss during exercise were compared between summer and winter.Methods: Sweat samples were collected from ten healthy adult males. Bicycle ergometer exercise was conducted by each subject at a heart rate of 140 beats/min for 1 hour, in summer and in winter. Sweat was collected by the arm bag method.Results: Concentrations of major (Na, K, Ca, and Mg) and trace elements (Zn, Cu, Fe, Ni, Mn, and Cr) in sweat tended to be lower in summer than in winter, and significantly lower concentrations of Mg (p<0.01), Na, Cu, and Mn (p<0.05) were found in summer. The sweat volume in summer (0.90 L) was 1.7-fold larger than that in winter (0.52 L) (p<0.01). The amount of loss of each element to sweat calculated from the concentrations in sweat and sweat volume showed no significant difference between summer and winter.Conclusions: It is suggested that there was no significant difference in the amount of loss of trace elements in sweat due to exercise between summer and winter.

The relationship between endurance time and fatigue factors at varying intensities in handgrip isometric exercise / 体力科学

The purpose of the present study was to investigate the relationship between endurance time and fatigue factors at varying intensities of handgrip isometric exercise. Seven subjects performed isometric contractions at 10%, 30% and 50% of maximum voluntary contraction (MVC) sustained to exhaustion. Continuous changes in high-energy phosphates and muscle oxygen content (oxy-Hb/Mb) in the forearm flexor muscle were measured by <SUP>31</SUP>P magnetic resonance spectroscopy (<SUP>31</SUP>P-MRS) and near infrared spectroscopy (NIRS), respectively. The endurance time to exhaustion was 963±236 (mean±S. D.), 209±41.9 and 95.3±13.6s at 10%, 30% and 50%MVC, respectively, From the onset of exercise at each %MVC, both PCr and oxy-Hb/Mb fell and Pi (H<SUB>2</SUB>PO<SUB>4</SUB>-) rose linearly with time, whereas intracellular pH remained relatively constant at resting values during the early phase. Thereafter, intracellular pH showed a linear decline. The rates of pH decline were 0.03±0.02, 0.22±0.14 and 0.51±0.17 pHunit/min, while the rates of H<SUB>2</SUB>PO<SUB>4</SUB>- increase were 20.9±19.3, 118±48.9 and 434±242 (% of resting) /min at 10%, 30% and 50%MVC, respectively. There were correlations between the changes in endurance times to exhaustion and the rates of pH decline (r= -0.58--0.87) and H<SUB>2</SUB>PO<SUB>4</SUB>- increase (r=-0.37--0.74, (n=7) ) at each intensity of exercise. In particular, significant correlations (p<0.05) between endurance time and the rate of pH decline were found at both 10% and 30%MVC. These results suggest that muscle fatigue (endurance time) at each intensity in handgrip isometric exercise is closely correlated with the rate of pH decline.

Effects of repeated exercise on muscle soreness, creatine kinase activity and white blood cell count / 体力科学

A study was conducted to investigate changes in muscle soreness, serum creatine kinase (CK) activity and white blood cell (WBC) count following exercise bouts spaced three weeks apart.<BR>The subjects were six male students (aged 23-25 yr), who had not participated in any training program for over 18 months. They performed muscular exercise of the nondominant arm using elbow flexors. Twenty percent of maximum voluntary contraction was used as the exercise intensity. After three weeks, the subjects repeated the same exercise bout. Perceived muscle soreness, CK activity and WBC count were assessed before, immediately after, 6h after and over 9 days after each exercise bout.<BR>After the first exercise bout (1 st Ex), the subjects experienced muscle sorenss for 3-7 days. Also, a large increase of CK was found in five subjects (266-763%) . When the peak CK efflux was observed (day 3-4 after exercise), soreness had almost disappeared. WBC count was increased immediately and 6 h after exercise, then returned to the resting level. However, a significant increase (p<0.05) in WBC count was observed again on day 7 after exercise when CK had returned to the resting level. After the second exercise (2 nd Ex), a significant decrease of muscle soreness and the CK response was found in comparison with the 1 st Ex (p<0.41) . One interesting feature was that the CK efflux of subjects who had shown a large increase of CK after the 1 st Ex was not increased after the 2 nd Ex.<BR>The initial exercise bout may have induced some damage to the muscle fibers or mem. bran. This damage would induce a process of repair in the damaged tissue, which in turn would adapt the muscle to the next stimulus. However, the subjects who showed a slight increase of CK after the 1 st Ex did not show this adaptation. Therefore an adaptive threshold for fiber or membrane damage may exist.

PHYSIOLOGICAL STUDY OF RACE-WALKING / 体力科学

The purpose of this study was to clarify some of the characteristics of race-walking, especially the relationship between walking speed and oxygen requirement, and stride in race-walking and normal walking, and to examine whether race-walking is effective for the maintenance and promotion of health.<BR>The subjects were five male race-walkers (race-walker group) and five male college students (control group) .<BR>The results obtained were as follows:<BR>1. Under race-walk conditions, the highest speeds attained in the race-walker and control groups were 200-220 m/min and 160 m/min, respectively. Under normal walking conditions, however, the values were 140 m/min in both groups.<BR>2. A lower oxygen requirement was observed at slower speed during normal walking and at a higher speed (over 130 m/min) during race-walking.<BR>3. Oxygen requirement (ml/kg/100 m) in the race-walker group was minimal at 60-80 m/min during race-walking and at 60 m/min during normal walking. Values in the control group were minimal at 60 m/min under both walking conditions.<BR>4. The oxygen requirement in the race-walker group was less than that of the control group under both walking conditions.<BR>5. Under normal walking conditions, as the speed increased, both step-length and step frequency gradually increased, until step-length reached a limit of 80 cm. Thereafter, walking was maintained only by an increase in step frequency. However, in the race-walkes group, the subjects were capable of increasing their step-length further, and maintaining a higher speed (up to 220 m/min) .<BR>6. It was suggested that race-walking is one of the most efficient exercises for maintaining and improving health.

Physiological study of race-walking. The relationship between walking speed and oxygen requirement / 体力科学

The purpose of this study was to clarify some of the characteristics of race-walking, especially the relationship between walking speed and oxygen requirement, and stride in race-walking and normal walking, and to examine whether race-walking is effective for the maintenance and promotion of health.<BR>The subjects were five male race-walkers (race-walker group) and five male college students (control group) .<BR>The results obtained were as follows:<BR>1. Under race-walk conditions, the highest speeds attained in the race-walker and control groups were 200-220 m/min and 160 m/min, respectively. Under normal walking conditions, however, the values were 140 m/min in both groups.<BR>2. A lower oxygen requirement was observed at slower speed during normal walking and at a higher speed (over 130 m/min) during race-walking.<BR>3. Oxygen requirement (ml/kg/100 m) in the race-walker group was minimal at 60-80 m/min during race-walking and at 60 m/min during normal walking. Values in the control group were minimal at 60 m/min under both walking conditions.<BR>4. The oxygen requirement in the race-walker group was less than that of the control group under both walking conditions.<BR>5. Under normal walking conditions, as the speed increased, both step-length and step frequency gradually increased, until step-length reached a limit of 80 cm. Thereafter, walking was maintained only by an increase in step frequency. However, in the race-walkes group, the subjects were capable of increasing their step-length further, and maintaining a higher speed (up to 220 m/min) .<BR>6. It was suggested that race-walking is one of the most efficient exercises for maintaining and improving health.

Effects of physical training on red blood cell properties, in particular red cell 2,3-DPG and aerobic work capacity / 体力科学

The purpose of this study was to examine the effects of physical training on red blood cell properties, in particular red cell 2, 3-diphosphoglycerate (2, 3-DPG) and aerobic work capacity. The subjects were 28 healthy men and they were divided into three groups: Group 1 (12 athletes-long distance runners, cross country skiers performing daily aerobic training), Group 2 (8 athletes-sprinters (400 m), alpine skiers playing aerobic and anaerobic training every day) and Control (8 untrained persons) .<BR>The results obtained were as follows:<BR>1) In aerobic work capacity (VO<SUB>2</SUB>max/w, O<SUB>2</SUB> pulse max) there was significant difference (p<0.01) among 3 groups (Group 1>Group 2>Control) .<BR>2) Red blood cell properties (RBC, Hb, Hct) of each group showed no significant difference. However MCH, MCHC of Group 1 was significantly lower than Group 2 and Control, MCV was also a tendency to be lower. Red cell 2, 3-DPG concentration was significantly higher in Group 1, 2 as compared with Control. But there was no significant difference between Group 1 and Group 2.<BR>3) Red cell distribution curve of Group 1 tended to shift to the left in comparison with other two groups.<BR>4) The relationship between VO<SUB>2</SUB>max/w and red cell 2, 3-DPG significantly correlated for all subjects composing the three groups. In addition a significant correlation was found for Group 1.