Sweating responses during activation of the muscle metaboreflex in humans is altered by time of day

AIM

The aim of the present study was to test for a time-of-day effect on sweating responses to activation of the muscle metaboreflex.

METHODS

Eight male subjects each participated in two exercise sessions, one in the morning and one in the evening. Within each session there were two 60-s bouts of isometric handgrip (IHG) exercise at 50% maximal voluntary contraction. Prior to IHG, whole body warming by a water-perfused suit initiated mild sweating. The first bout of IHG exercise began at 06.00 hours (am) and 18.00 hours (pm). Blood circulation to the forearm was occluded for 120 s, beginning 5 s before the end of the second bout of IHG to activate the muscle metaboreflex.

RESULTS

During both bouts of exercise, sweating rate (SR) on both the chest and right forearm significantly increased from the pre-exercise period in both am and pm sessions. SR rapidly decreased during first minute of recovery after the first bout of IHG exercise. However, during post-exercise ischaemia (PEI) after the second bout of IHG exercise, SR was maintained significantly above the pre-exercise level only in the pm session. The increases in SR on the chest and right forearm during PEI were significantly greater in the pm, than in the am, session. However, SR of the palm was not maintained during PEI.

CONCLUSIONS

We conclude that under mild hyperthermic conditions, the sweating response in non-glabrous skin to activation of the muscle metaboreflex exhibits a time-of-day effect.

Changes in surface EMG and acoustic myogram parameters during static fatiguing contractions until exhaustion: influence of elbow joint angles

The purpose of this study was to evaluate muscle fatigue using electromyogram (EMG) and acoustic myogram (AMG) signals of the shoulder and arm muscles during sustained holding tasks, with the elbow at different angles and at different levels of maximum voluntary contraction (MVC). The EMG and AMG of four muscles, including the upper trapezius (TP), anterior deltoid (DL), biceps brachii (BB), and brachioradialis (BR), were recorded during experiments using 10 healthy young males. The experiments were conducted under 9 pairs of conditions: 3 elbow angles (120 degrees, 90 degrees, and 60 degrees) and *3 levels of %MVC (20%, 40%, and 60%). Subjects were instructed to hold a weight equal to the designated %MVC at designated joint angles and asked to maintain that condition for as long as possible until exhaustion. Joint angles were also recorded by the electrogoniometers. The analysis of variance revealed that there was no significant effect of elbow angle on the mean MVC or on the endurance time. Elbow angle showed a significant effect on mean power frequency (MPF) of EMG in DL, BB, and BR, and a significant effect on root mean square (RMS) of EMG in four muscles. In BB and BR, MPF of EMG at 120 degrees was found to be significantly lower than 90 degrees and 60 degrees, respectively. There was a significant main effect of elbow angle on MPF of AMG for TP at 20% MVC; for DL at 20% and 40% MVC; for BB at 40% and 60% MVC; and for BR at the three levels of %MVC. The results showed that the range MPF of AMG for DL, BB, and BR was between 32 to 46 Hz, whereas that for TP was from 49 to 83 Hz. There was a significant effect of elbow angle on RMS of AMG in all four muscles in all experiments. At 20% MVC, a progressive increase in RMS of AMG was observed with time. In contrast, at 40% and 60% MVC, RMS showed very different behavior; specifically, it was found that RMS of AMG at 20% MVC significantly increased with increase of elbow angle. We conclude that RMS of AMG has a good and clear correlation with elbow angle at a low level of contraction.

The effects of hedonic properties of odors and attentional modulation on the olfactory event-related potentials

The purpose of this study was to investigate the influence of the hedonic properties of odors and the attention of subjects on components of the olfactory event-related potentials (OERP). The subjects were seven healthy male students. Two odors (orange and eugenol) of different hedonic properties were presented to the subjects via a constant-flow olfactometer during an oddball paradigm under ignore and attend conditions, and the OERP were then established. The latencies of the OERP were not affected by the qualitatively different odors, whereas the amplitude of late positive component (P3) during the presentation of orange was significantly larger than that during the presentation of eugenol. On the other hand, the allocation of a subject's attention led to a decrease in the latency and to an increase in the amplitude of P3. Moreover, the amplitude of P3 increased significantly when the pleasant odor (orange) in the rare stimulus was presented under the attend condition. These results suggested that hedonic property, distribution of attention, and the interaction between these factors may influence the OERP components.

The effect of mental loads on muscle tension, blood pressure and blink rate

Surface electromyogram (EMG), blood pressure (BP), blink rate (BR) and heart rate (HR) were recorded before and during 4 types of mental task. The mental task involved 3 tasks that encompassed the memory (M), visual search (VS) and color-word (CW) tasks besides the control task (CT) of maintaining a similar posture while focusing on a single spot on the computer screen. Except for CW, any voluntary movement for response to visual stimuli given were not demanded. Slightly but significant increases in integrated EMG (iEMG) were shown in terapezius, biceps and gastrocnemius muscles during tasks except for CT. Especially in the trapezius muscle during M, the most remarkable enhancements of iEMG and BP were shown. In VS and CW tasks, significant decreases in BR were observed, although in M and CT tasks there were no significant changes in it. There were no significant changes in HR in any type of tasks. The present study demonstrated the increase in muscle tension due to mental needs of cognitive tasks per se accompanying changes in BP and BR. And, enhancement of these physiological responses by memory loads and eyeball movement was discussed as a possible mechanism.

Automatic control of a robot camera for broadcasting based on cameramen's techniques and subjective evaluation and analysis of reproduced images

With the goal of achieving an intelligent robot camera system that can take dynamic images automatically through humanlike, natural camera work, we analyzed how images were shot, subjectively evaluated reproduced images, and examined effects of camerawork, using camera control technique as a parameter. It was found that (1) A high evaluation is obtained when human-based data are used for the position adjusting velocity curve of the target; (2) Evaluation scores are relatively high for images taken with feedback-feedforward camera control method for target movement in one direction; (3) Keeping the target within the image area using the control method that imitates human camera handling becomes increasingly difficult when the target changes both direction and velocity and becomes bigger and faster, and (4) The mechanical feedback method can cope with rapid changes in the target's direction and velocity, constantly keeping the target within the image area, though the viewer finds the image rather mechanical as opposed to humanlike.

Development and evaluation of the measurement system for the human shoulder joint based on the 6 DOF kinematic modelling

Although numerical models on the shoulder complex joint are currently available, many are impractical because of the procedural complexity coupled with limited and mere simple simulations. The present study defined the clavicle-scapula system as the "base of the humerus" in determining the position of proximal head of humerus, rendering conclusive innovation of a six degree of freedom (DOF) shoulder complex joint model. Furthermore, a complete measurement system where evaluation by calibrating the actual values via the use of an electromagnetic tracking device (ETD) was developed based on the innovated model. The special calibration method using optimizing calculation to work out the rotational center of humerus was employed and actually tested if the theoretical consideration was practically available. As a result of accuracy check experiments, the measurement error was defined within 2-3 mm, indicating sufficient accuracy in studies for human movement. Our findings strongly advocate that the benefit of this novel measurement system would contribute to studies related to shoulder movements in physiological anthropology.

Effects of inhalation of essential oils on EEG activity and sensory evaluation

The purpose of this study was to investigate EEG changes in subjects directly after inhalation of essential oils, and subsequently, to observe any effect on subjective evaluations. EEG and sensory evaluation were assessed in 13 healthy female subjects in four odor conditions. Four odor conditions (including lavender, chamomile, sandalwood and eugenol) were applied respectively for each subject in the experiment. The results were as follows. 1) Four basic factors were extracted from 22 adjective pairs by factor analysis of the sensory evaluation. The first factor was "comfortable feeling", the second "cheerful feeling", the third "natural feeling" and the fourth "feminine feeling". In the score of the first factor (comfortable feeling), the odors in order of high contribution are lavender, eugenol, chamomile and sandalwood. 2) Alpha 1 (8-10 Hz) of EEG at parietal and posterior temporal regions significantly decreased soon after the onset of inhalation of lavender oil (p < 0.01). Significant changes of alpha 1 were also observed after inhalation of eugenol or chamomile. The change after inhalation of sandalwood was not significant. These results showed that alpha 1 activity significantly decreased under odor conditions in which subjects felt comfortable, and showed no significant change under odor conditions in which subjects felt uncomfortable. These results suggest a possible correlation between alpha 1 activity and subjective evaluation.

Comparison of predictive value for colorectal cancer in subjects with and without rectal bleeding

BACKGROUND/AIMS

To clarify the association between a sign of rectal bleeding and colorectal cancer, and to reveal the relationship of rectal bleeding to the results of an immunochemical fecal occult blood test.

METHODOLOGY

In a population-based cross sectional study, 30,138 subjects who received immunochemical fecal occult blood screening with a 2-day method were divided into two groups, according to the results of a questionnaire on a sign of rectal bleeding, and the positivity rate of an immunochemical occult blood test as well as the predictive value for colorectal cancer were compared in the two groups.

RESULTS

The fecal occult blood test was positive in 8.8% of subjects with rectal bleeding and in 6.0% of subjects without rectal bleeding, and the predictive value was 6.4% and 3.3% in subjects with and without rectal bleeding, respectively, showing a significant difference in the positivity rate (p<0.001) as well as the predictive value (p<0.05) between these two groups.

CONCLUSIONS

These findings indicate that there are positive relations between the subjects with rectal bleeding presentation and colorectal cancer, and a sign of rectal bleeding and the results of an immunochemical fecal occult blood test.

Evaluation and design of a small portable EMG amplifier with potential RMS output

The present study attempted to design and evaluate a small portable electromyogram (EMG) amplifier that can output enhanced EMG and its root mean square (RMS) value. The production and design were of a laboratory scale without any special or high cost circuit construction. The designed amplifier was actually innovated according to the actual working conditions based on physiological anthropology. The present amplifier was compared with commercially available products and proved to be of practical use. The device was installed with a sufficiently small body depicting 8-channel variable gain AC amplifier and variable time-window RMS-to-DC converter. The prototype was battery-driven and well-shielded to minimize external noise interference.

Estimation of thermal sensation during varied air temperature conditions

Seven male students were exposed to four varied air temperature environments: hot (37 degrees C) to neutral (27 degrees C) (HN), neutral to hot (NH), cool (17 degrees C) to neutral (CN), and neutral to cool (NC). The air temperature was maintained at the first condition for 20 min, then was changed to the second condition after 15 min and was held there for 20 min. Each subject wore a T-shirt, briefs, trunks, and socks. Each sat on a chair and was continuously evaluated for thermal sensation, thermal comfort, and air velocity sensation. Some physiological and thermal parameters were also measured every 5 s during the experiment. The correlation between thermal sensation and skin temperature at 15 sites was found to be poor. The subjects felt much warmer during the rising phase of the air temperature (CN, NH) than during the descending phase (HN, NC) at a given mean skin temperature. However, thermal sensation at the same heat flux or at the same value of the difference between skin and air temperature (delta(Tsk - Ta)) was not so different among the four experimental conditions, and the correlation between thermal sensation and heat flux or delta(Tsk - Ta) was fairly good. The multiple regression equation of the thermal sensation (TS) on 15 sites of skin temperature (Tsk; degrees C) was calculated and the coefficient of determination (R*2) was found to be 0.656. Higher coefficients of determination were found in the equations of thermal sensation for the heat flux (H; kcal.m-2.h-1) at the right and left thighs of the subjects and on delta(Tsk - Ta) (degrees C) at 4 sites. They were as follows: TS = 2.04 - 0.016 Hright - 0.036 Hleft; R*2 = 0.717, TS = 1.649 + 0.013 delta(Tsk - Ta)UpperArm - 0.036 delta(Tsk - Ta)Chest - 0.223 delta(Tsk - Ta)Thigh-0.083 delta(Tsk - Ta)LowerLeg; R*2 = 0.752, respectively.

Control of circadian variation in skin blood flow response to heat stress

Six male subjects had their lower legs immersed in water at 42 degrees C for 60 min at 4 different times of the day to study whether the skin blood flow response to passive heat stress shows circadian variation in the relationship between skin blood flow and local sweating rate. When skin blood flow was plotted against local sweating rate, three distinct phases were observed. Phase A, an increase in skin blood flow without sweating was maximal at night. But the slope of the regression line did not change over the day in Phase C. These findings suggest that there is circadian variation in the skin blood flow response before onset of sweating during passive heat stress. This variation might be related, in part, to the circadian rhythm in vasoconstrictor activity.

Circadian variation in skin blood flow responses to passive heat stress

To examine whether there is a circadian variation in skin blood flow response to passive heat stress and maximal skin blood flow, which was measured by local warming to 42 degrees C for 45 min, we studied six men at an ambient temperature of 28 degrees C at four different times of day [0400-0700 (morning), 1000-1300 (daytime), 1600-1900 (evening), and 2200-0100 hours (night)], each time of day being examined on separate days. Heat stress at rest was performed by immersing the legs below the knee in hot water (42 degrees C) for 60 min. The esophageal temperature (Tes) at rest was significantly higher in the evening than in the morning. The maximal skin blood flow (SkBFmax) on both sites, back and forearm, did not show a significant difference among the four times of day. The variation in Tes thresholds for cutaneous vasodilation to heat stress was similar to the circadian rhythm in resting Tes. The relationship of the percentage of SkBFmax (%SkBF) with Tes was significantly lower in the morning than in the evening. The results suggest that the maximal skin blood flow during local warming does not show variation over the day, but the sensitivity of vasodilation to passive heat stress shows a circadian variation.

Circadian variation of sweating responses to passive heat stress

The aim of present study was to examine whether sweating responses to passive heat stress change with the circadian rhythm of internal temperature. Six men had their legs immersed in water at 42 degrees C for 60 min in an ambient temperature of 28 degrees C on four separate days. Experiments were conducted at four different times [06.00 h (morning), 12.00 h (daytime), 18.00 h (evening) and 24.00 h (night)]. We measured oesophageal temperature (Toes), mean body temperature (Tb), local sweating rate (msw) on the forehead, back, forearm and thigh, the densities of activated sweat gland (ASG) on the back, forearm and thigh, and the frequency of sweat expulsion per minute (Fsw) which has been suggested to represent central sudomotor activity. Sweat gland output (SGO) on each site was calculated by dividing msw by ASG. ASG was significantly higher on the forearm than on the back and thigh, and SGO was significantly lower on the forearm than on the back and thigh. However, ASG and SGO did not significantly change over the day. Tb and Toes thresholds for the onset of sweating showed a significant change with both the temperature rhythms at rest prior to each procedure, while the slopes of the relationships Fsw-Tb and msw-Fsw showed no significant difference over the day. We suggest that the circadian variation of sweating response to passive heat stress is regulated by a central sudomotor mechanism rather than by sweat gland function.

Basic study on the rectangular numeric keys for touch screen

The present study was conducted to examine the optimum inter-key spacing of numeric rectangular keys for touch screens. Six male students (22-25 years old) and three female students (21-24 years old) participated in the experiment. Each subject performed the data entry task using rectangular keys of touch devices. These keys were arranged in both horizontal and vertical layouts. The sizes of the rectangular keys in both layouts were 12 x 21 mm and 15 x 39 mm, and each of the inter-key spacing of each key was 0, 3, 6, 12 and 21 mm. The response time with inter-key spacing of 3 mm was significantly faster than with the inter-key spacing of 0, 12 and 21 mm (p < 0.05). Keys of vertical position produced faster response time than that of horizontal position. The subjective ratings showed that the inter-key spacing of 6 mm was significantly better than the inter-key spacing of 0, 3, 12 and 21 mm (p < 0.05).

Fundamental study on the size and inter-key spacing of numeric keys for touch screen

The purpose of this study was to reveal the optimum size and inter-key spacing of numeric square keys for touch screens. Six male students (22-25 years old) and three female students (21-24 years old) volunteered as subjects for this experiment. Each subject took part in data entry tasks using numeric square keys of touch devices. The sizes of keys were 6, 12, 21, 30 and 39 mm and each the inter-key spacing was 0, 3, 6, 12 and 21 mm. Response times with key sizes of 6 and 12 mm were significantly slower than with key sizes of 21 and 30 mm (p < 0.001). Furthermore, the key size of 6 mm significantly caused more errors than the key sizes of 12, 21, 30 and 39 mm (p < 0.05). The response time with inter-key spacing of 3 mm was significantly faster than with that of 0, 6, 12 and 21 mm (p < 0.001). Inter-key spacing of 0 mm significantly produced more errors than other inter-key spacing. Subjective ratings for inter-key spacing of 3, 6 and 12 mm were significantly better than those of 0 and 21 mm (p < 0.05). These results suggested that the optimum size of numeric square keys for touch screens should be more than 21 mm and optimum inter-key spacing should be from 3 to 6 mm. Optimum key size, however, must be selected with regard to the limitation of screen size.

Effects of cooling portions of the head on human thermoregulatory response

Seven healthy young male students participated in this study. Each subject sat on a chair in an anteroom at 25 degrees C for 30 min and then entered a climatic chamber, controlled at 40 degrees C and R.H. 50%, and sat on a chair for 90 min. Cooling of frontal portion including the region around the eyes (FC), occipital portion (OC), and temporal portion (TC) began after 50 min of entering. An experiment without head cooling (NC) was also made for the control measurement. Thermal comfort and thermal sensation were improved by head cooling, but response was the same regardless of portion cooled. Although rectal temperature, mean skin temperature and heart rate showed no significant effect due to head cooling, forearm skin blood flow (FBF), sweat rate (SR), and body weight loss (delta Wt) had a tendency to be depressed. FBF in FC and TC decreased during head cooling, but that in OC and NC did not change significantly, while SR in FC was depressed. delta Wt showed total sweating to decrease by FC and TC, and FC to have greater inhibitory effect on sweating than OC. Thermal strain was evaluated by the modified Craig Index (I(s)). I(s) in FC decreased significantly more than in NC. Cooling of other portions of the head had no significant effect on I(s). Cooling of the frontal portion of the head may thus be concluded to have the most effect on thermoregulatory response in a hot environment.

Characteristics of Roman character input in Japanese word processing on keystroke interval time

This study clarifies the characteristics of the time keys that are taken to enter Roman letters for Japanese sentences. First, test the appearance frequency of two consecutive characters of the alphabet in the input of English sentences and in the input of the Roman characters of Japanese sentences. Based on these results, we analyzed the features of stroke frequency of the keys in the Roman character input. Based on the result of the analysis, we clarified the features of the keystroke interval time for two consecutive characters in the Roman character input. Then, keys were struck to enter Japanese sentences for a fixed period of time and a test was made for the characteristics. As a result, the following points were clarified: 1) The time keys struck were divided into two large groups. One for two consecutive alphabet letters that corresponded to Kana, or the Japanese syllabary, and the other with no correspondence. The former had smaller values for the mean time and deviations, and the latter had larger values for them. 2) The subjects who struck a larger number of keys per unit time took less time in typing two consecutive letters which did not correspond to Kana.

Comparative study on the muscular load of the arms using hair driers

The purpose of the present study was to evaluate the muscular load of the arm when combing the hair using different "kuru-kuru" type of hair driers. Ten female students (20-24 years old) volunteered as subjects. Five combing patterns were conducted as follows: 1) comb outer layer of right side of hair using right hand, 2) comb outer layer of left side of hair using right hand, 3) comb inner layer of left side of hair using right hand, 4) comb outer layer of back hair using right hand, and 5) comb inner layer of right side of hair using left hand. Surface EMGs were recorded from M. flexor carpi ulnaris, M. brachioradialis, M. biceps brachii, M. triceps brachii, M. deltoideus and M. trapezius of both sides of body. Integrated EMGs (iEMGs) were used to evaluate muscular load for each of the seven different types of hair driers used. The relationship between iEMGs and weight, center of gravity, diameter, length, and circumference of each hair drier were examined. The weight of hair driers tended to be the effective factor on the muscular load. Muscular load also had a tendency to be affected by the shape of the grips. With regard to the hand size, the longer the thumb length, the smaller is the muscular load. It was suggested that a relatively large diameter of the bulb-shaped grip of the drier gave a smaller muscular load among the hair driers examined in the present experiment.

Effects of time stress on psychophysiological responses during data entry tasks

Six male and six female students (19-23 yrs) volunteered as subjects in the present experiment. Subjects performed the data entry tasks. A hundred and twenty single digit numbers 12 by 10 lines matrix were displayed in a random sequence on the left side of monitor. Subjects input the same numeral as these numbers one by one with clicking of the mouse on the ten keys displayed on the right side of the monitor. Each task consists of the following conditions: 1) system response time is fast or slow; 2) delete the input numerals from 120 numbers or not; 3) button flashes after input or not; and 4) the remaining time is displayed or not during performing the tasks. These tasks are programmed to be finished automatically after 200 seconds independent of the rate of completing all inputs. We measured heart rate (HR), systolic and diastolic blood pressure (SBP and DBP), skin blood flow (SBF), skin potential level (SPL), number of errors (Es), total number of input and subjective ratings concerning the degree of irritation (SR1), difficulty of input (SR2) and unpleasantness in operation (SR3). It was shown that when system response time was slow, even the average of heart rate and blood pressure were lower than fast system response time, however, the subjects felt greater emotional irritation, difficulty of input and unpleasantness in operation hence making more errors.

Changes in body shape of young individuals from the aspect of adult physique model by factor analysis

The purpose of this study was to clarify characteristics of age-related changes in body shape in adolescence, in 11- to 19-year-old boys and girls, by using previously reported physique models of adult men and women as the scale. The scale consisted of four factors obtained by factor analysis using 30 items as variables, such as the values measured for the physique, skinfold thickness and body composition. The four factors were Factor 1: body fat, Factor 2: mass, Factor 3: leg length to height ratio, and Factor 4: length, and were interpreted in the men and women in a similar manner. The subjects were 307 boys and 368 girls; all were healthy. Thirty items were measured and included the values measured for the physique, skinfold thickness and body composition, as in the men and women. Factor scores in the subjects were standardized by mean and standard deviation for each item in the adult subjects, and calculated for individuals by using the coefficient of factor score in the adult subjects. The body shapes of the boys and girls were investigated from the factor score by age calculated for each factor. The following results were obtained: 1. Factor 1 tended to gradually decrease and reached the adult level at 15 years of age in the boys.(ABSTRACT TRUNCATED AT 250 WORDS)

Circulatory regulation during supine and sitting intermittent isometric handgrip in a hot environment

We studied the circulatory regulation during intermittent isometric handgrip (IIHG, six seconds contraction + six seconds relaxation) in supine and sitting postures in a hot environment (40 degrees C, RH: 50%). Eight healthy male subjects performed thrice 5-minute period IIHG at three different work loads (10%, 20% and 30% MVC). The IIHG was performed with the right hand in the two postures. Heart rate (HR), cardiac output (CO), mean arterial blood pressure (MBP), forearm blood flow (FBF), skin blood flow (SBF), foot swelling (FSW) and tympanic temperature (Tty) were measured during IIHG, resting and recovery periods. During IIHG in a hot environment, HR, MBP, FSW and Tty showed higher values in the sitting than in the supine posture. FBF during relaxation showed higher values at high work load than at low work load in the two postures. FBF showed higher values in the sitting than in the supine posture, except during relaxation at 30% MVC. It was concluded that the decrements of blood volume of splanchnic organs might be greater in the sitting than in the supine posture due to sympathetic vasoconstrictor activity, and were responsible for the redistribution of blood flow. Posture had an effect on FBF because of hydrostatic pressure.

Different behavior of forearm blood flow during intermittent isometric handgrip in a thermo-neutral and a hot environment

The purpose of the present study was to evaluate the different behavior of forearm blood flow (FBF) during intermittent isometric handgrip (IIHG, 6 seconds contraction +6 seconds relaxation) in a thermoneutral versus a hot environment. Six healthy men performed three times of 5-minute period IIHG at three different work loads (10%, 20% and 30% MVC). The IIHG was performed with the right hand. The experiments of IIHG were performed at two different air temperatures (25 degrees C and 40 degrees C, RH: 50%), and an experiment without work was also carried out at 40 degrees C (RH: 50%). The physiological responses measured involved heart rate (HR), cardiac output (CO), mean arterial blood pressure (MBP), FBF, and skin blood flow (SBF). HR, CO and SBF showed higher values during IIHG at 40 degrees C than at 25 degrees C. MBP had a tendency to increase with the intensity of work load at both 25 degrees C and 40 degrees C. Since intramuscular pressure might increase during contraction periods at 20% MVC and 30% MVC at 25 degrees C, FBF was significantly higher during relaxation periods than during contraction periods. FBF showed similar values between contraction and relaxation periods at 10% MVC at both temperatures. The present study suggested that FBF was sufficient for active muscles during IIHG at 10% MVC. FBF of contraction periods was close to that of relaxation periods at 40 degrees C due to the modulation of the sympathetic outflow to the muscles and/or the decreased efficiency of the muscle pump. It was suggested that FBF showed different behaviors during HHG at 25 degrees C versus at 40 degrees C.

Characteristics of body shape of female athletes based on factor analysis

We examined the body shape of female athletes in comparison with female adult non-athletes by factor analysis. The subjects were 433 adult non-athletes and 464 athletes participating in 11 different sporting events. The physique, skinfold thickness and body composition of each subject were measured. The values obtained from non-athletes were analyzed by factor analysis, and the body shape of the athletes was then analyzed according to these factors. Four main factors with which 80 percent of total variance could be explained were body fat (Factor 1), mass (Factor 2), leg length to height ratio (Factor 3) and length (Factor 4), and were extracted from the values from non-athletes. The body shape of the athletes could be classified into 4 categories by cluster analysis for factor score of sporting events: less body fat and slim type, average type like non-athletes, muscular and well-balanced type, and tall and well-developed mass. Compared with non-athletes, female athletes for all sporting events had less body fat. Moreover, the athletes had a body shape suitable for their sporting events; i.e., their mass, length of leg and height.

Classification of body shape of male athletes by factor analysis

The purpose of this study was to evaluate the body shape of athletes in comparison with adult non-athletes by factor analysis. The subjects were 210 male adult non-athletes and 485 male high school age and adult athletes participating in 13 different sporting events. Physique, skinfold thickness and body composition of each subject were measured. Measured values from adult non-athletes were analyzed by factor analysis, and body shape of the athletes was then analyzed according to these factors. The results are summarized as follows: 1. Four main factors, that is, body fat, mass, leg length to height ratio and length, which could explain 88.5 percent of total variance, were extracted from the measured values from adult non-athletes. 2. Similarity of body shape between sporting events was analyzed by cluster analysis. Body shape of the athletes could be classified into 3 categories: muscular and well-balanced type; rich muscular and large-built type; and rich muscular and long-torso type. Compared with adult non-athletes, male athletes had less body fat and greater mass except for long-distance runners. The present results suggested that the athletes had body shapes suitable to their sporting events.

[Localized muscular load to different work patterns and heat loads during handgrip]

The physiological responses and the magnitude of perceived fatigue (MPF) were estimated from eight healthy men during isometric continuous and intermittent handgrip at 10% maximum voluntary contraction (MVC). The physiological responses involved electromyogram (EMG), heart rate (HR), mean blood pressure (MBP) and forearm blood flow during contraction (FBFC) and relaxation (FBFR). The sequence of tests included three different work patterns: 1) continuous handgrip for 30 min, 2) intermittent handgrip (10 sec contraction +5 sec relaxation) for 45 min, 3) intermittent handgrip (10 sec contraction +10 sec relaxation) for 60 min. These experiments were performed on two different heat loads (25 degrees C and 40 degrees C, H.R. 50%). The results were as follows: 1) The localized muscle fatigue in the forearm was observed during the work periods. 2) The mean frequency of EMG was higher at 40 degrees C than 25 degrees C. 3) FBFR was significantly lower than FBFC at 40 degrees C. 4) MPF and MBP were little influenced by the heat load. 5) MPF correlated well with both HR and MBP.

[Effects of handgrip work and heat load on heart rate variability]

The purpose of the present study was to evaluate cardiac sympathetic (SNS) and parasympathic (PNS) nervous system activities during isometric continuous and intermittent handgrip with power spectrum analysis of heart rate variability (HRV). Eight healthy men performed work at 10% maximum voluntary contraction. The sequence of tests included three different work patterns: 1) the continuous handgrip for 30 min, 2) the intermittent handgrip (10 sec contraction +5 sec relaxation) for 45 min, 3) the intermittent handgrip (10 sec contraction +10 sec relaxation) for 60 min. These experiments were performed at two different heat loads (25 degrees C and 40 degrees C, R.H. 50%). To evaluate HRV, low frequency component (0.03-0.15Hz: LFP) and high frequency component (0.15-0.5Hz: HFP) power were calculated. The SNS and PNS activities were evaluated by LFP/HFP and HFP/(HFP + LFP), respectively. Summary of the results was shown below. 1) The change of the SNS and PNS activities were not significant among the different work patterns, due to the lower work load in the present experiment. 2) The increase of HR at 25 degrees C was mediated primarily by the decrease of the PNS activities during the work periods. 3) The effects of heat loads on the SNS and PNS activities were significant. Briefly, at the same work pattern, the SNS activities at 40 degrees were higher than those at 25 degrees C, but the PNS activities at 40 degrees C were lower than those at 25 degrees C.

[Responses of electroencephalogram to different odors]

The responses of electroencephalogram (EEG) to different odors and their densities were studied on four men and two women at rest while sitting. The odors examined were citrus, floral and lavender, and their densities were 100 ppb and 200 ppb. The odors were released for ten minutes from a duct to fill the room completely. The subjective estimation indicated that citrus had a tendency to be the most comfortable odor in this study, but it was not significant. To evaluate changes of EEG, the power spectra of frequency-fluctuation of alpha wave (Fz) and the rate of alpha, beta, and beta/alpha wave (Oz, Fz) were calculated. The rate of alpha wave (Oz) in the period of giving out the citrus at 100 ppb was significantly (p < 0.05) higher than that of the lavender. The rate of beta wave (Oz) in the period of giving out the floral at 200 ppb was significantly (p < 0.05) higher than that of the lavender. The regression coefficient of the power spectra of frequency-fluctuation of alpha wave in the period of giving out the lavender at 100 ppb was significantly higher than those in the other periods of the experiment. The regression coefficient of the power spectra of frequency-fluctuation of alpha wave for lavender given out at 200 ppb was significantly (p < 0.01) higher than those for the other odors given out. It seems that the regression coefficient of the power spectra of frequency-fluctuation of alpha wave can be used for the evaluation of psychophysiological responses.

Development of a new device to measure local heat exchange by evaporation and convection

According to the principles of heat and mass transfer, the rate of local heat exchange by convection (C) and local heat loss by evaporation (E) can be estimated if temperature and vapor concentration profiles in the boundary layer are measured. In addition, temperature (Ts) and vapor concentration (rho s) at the surface may be predicted from the measured profiles. On this basis, a new device was developed to measure parabolic profiles by incorporating three relative humidity sensors coupled with thermistors into its probe. It has been evaluated from various tests including human experiments. The results showed that the device, with humidity sensors arranged perpendicular to the surface, could estimate C, E, Ts, and rho s in closer agreement with direct measurements when compared with the conventional gradient method. This confirmed that our method had clear advantages over the conventional gradient method under laminar air flow conditions.

Comparative studies on thermoregulatory responses to heat between Japanese Brazilians and Japanese

Eight male Japanese Brazilians (20-32 yrs) and 11 male Japanese (22-24 yrs) volunteered for this study. The Brazilians had been staying for about 2-21 weeks in Japan. Their physical characteristics are not significantly different from those of the Japanese. Each one of them sat on a chair for 45 min at 40 degrees C (R.H. 50%) in a climatic chamber. Then, they exercised using a bicycle ergometer in a semi-reclining position for 45 min at 40% of maximal oxygen uptake. Forearm blood flow (FBF), oxygen uptake (VO2), heart rate (HR), skin temperature (Tsk), sweat rate (SR) at chest region and body weight loss (delta Wt) were measured. Thermal sensation and thermal comfort were also measured. Thermal and comfort sensation confirmed that Japanese Brazilians felt cooler and more comfortable in 40 degrees C environment than the Japanese. VO2, SR and delta Wt for both groups were not significantly different. FBF and HR for Brazilians were significantly lower than those for Japanese. Tsk at chest region for Brazilians was found to be significantly higher than that for Japanese. Thus the thermoregulatory responses observed in Japanese Brazilians may be largely attributed to the climate in their native places located on the Tropic of Capricorn.

[Study of scanner counter for POS terminal system from view point of posture when take-out goods]

Recently, an increasing number of supermarkets have been introducing the point of sales (POS) system. The scanner counter of this POS system makes repetitive operations including taking goods out of basket, letting them pass through the scanner for their bar codes and then putting them in the next basket. The basket is about 25.5 cm deep, and the counter must be high enough to satisfy two conditions that the base surface and the upper edge of the basket are not too low and not too high, respectively to take goods out of it. In the present study, repetitive operations of taking goods from 16 spots at their respective different heights 49.5, 57.5, 65.5 and 73.5 cm of four corners of the basket was made to measure the posture, heart rate (HR) and electromyograms (EMG) on four sites (right shoulder and loin , left loin and right femoris) of the operator and to examine the height of the counter. EMGs on the right loin , left loin and right femoris showed significant differences (P less than 0.05) in case of goods' position, operator side less than contralateral side and of counter's height, 73.5 less than 65.5 less than 57.5 less than 49.5 cm. EMG on the right shoulder showed significant differences (P less than 0.05) in case of the goods' position, operator side less than contralateral side and of the counter's height, 73.5 cm greater than another height on operator side.

The lower and upper critical temperatures in male Japanese

Critical temperatures were determined by a new estimating system called the polynomial equation method. Its consists of polynomial regression equations of metabolic rate on ambient and body temperatures and conversion equations enable to convert metabolic rate value into temperature value. Nine young adult males were tested using the system. Metabolic rate was calculated indirectly with a reference to protein metabolism and the critical temperatures were determined as follows; the lower critical air temperature to be 26.2 C, the upper critical air temperature to be 47.0 degrees C, the lower and upper mean skin temperature to be 29.2 degrees C and 36.5 degrees C, and the lower and upper critical rectal temperature to be 35.5 degrees C and 37.9 degrees C, respectively. The polynomial equation method has an advantage over the intersect method since it allows estimation of several kinds of critical temperature.