下村 義弘

Purpose: Recent surgical techniques have been advancing under endoscopic view and insufflation of carbon dioxide gas to expand the abdominal cavity. Isotonic fluid could be one candidate for expanding cavities to facilitate surgical maneuvering. We tested the feasibility and drawbacks of replacement of irrigating materials using a porcine model (water-filled laparoendoscopic surgery [WAFLES]). Materials and Methods: Laparoscopic cholecystectomy was performed in two porcine models using instillation of sorbitol solution as irrigant. Solution irrigation was performed through one of four ports, with drainage via another port. Conventional forceps equipped with a monopolar electrode for electrocautery, laparoscope, video processor, ultrasound, and transducer for measuring intraabdominal pressure were used. Results: Laparoscopic cholecystectomy was successfully undertaken with the following benefits: (1) clear observation of the dissecting plane throughout maneuvering; (2) control of oozing and spilled bile by irrigation and suction; and (3) ultrasonographic and laparoscopic images can be obtained simultaneously without any restriction to probe location. However, two disadvantages should be noted: (1) difficulties in managing floating organs and (2) interruption of vision by blood. Conclusions: WAFLES provides some benefits for endoscopic surgery with proper devices, including apparatuses for irrigation and suction. Efficient irrigation and selection of proper irrigant and apparatuses are required to establish an acceptable procedure.

午前中に赤、緑、青の単波長光曝露を行い、その後の睡眠における生理応答と個人特性との関連実験を実施した。単波長光は638 nm(R)、523 nm(G)、465 nm(B)にピークを持つLED電球により曝露された。放射照度は被験者の目の位置でそれぞれ73.4 &mu;W/cm&sup2;(R)、74.2 &mu;W/cm&sup2;(G)、76.9 &mu;W/cm&sup2;(B)であった。結果は青色条件では赤色よりも夜間の直腸温の値が有意に（P < 0.01）高かった。さらに被験者内における直腸温の低下量（睡眠前の最高値－睡眠中の最低値）では、MEQスコアに対して青色条件で有意な強い正の相関（R&sup2;=0.73）を示した。従って、午前中の単波長光曝露が夜間の睡眠におよぼす影響について青色光の場合は直腸温の十分な低下を妨げ、睡眠リズムを弱めた。これらの効果は生活様式が夜型であるほど強かったと考えられる。

OBJECTIVE: In recent years, a new type of speaker called the parametric speaker has been used to generate highly directional sound, and these speakers are now commercially available. In our previous study, we verified that the burden of the parametric speaker was lower than that of the general speaker for endocrine functions. However, nothing has yet been demonstrated about the effects of the shorter distance than 2.6 m between parametric speakers and the human body. Therefore, we investigated the distance effect on endocrinological function and subjective evaluation. METHODS: Nine male subjects participated in this study. They completed three consecutive sessions: a 20-min quiet period as a baseline, a 30-min mental task period with general speakers or parametric speakers, and a 20-min recovery period. We measured salivary cortisol and chromogranin A (CgA) concentrations. Furthermore, subjects took the Kwansei-gakuin Sleepiness Scale (KSS) test before and after the task and also a sound quality evaluation test after it. Four experiments, one with a speaker condition (general speaker and parametric speaker), the other with a distance condition (0.3 m and 1.0 m), were conducted, respectively, at the same time of day on separate days. We used three-way repeated measures ANOVA (speaker factor x distance factor x time factor) to examine the effects of the parametric speaker. RESULTS: We found that the endocrinological functions were not significantly different between the speaker condition and the distance condition. CONCLUSION: The results also showed that the physiological burdens increased with progress in time independent of the speaker condition and distance condition.

In recent years, a new type of speaker called the parametric speaker has been used to generate highly directional sound, and these speakers are now commercially available. In our previous study, we verified that the burden of the parametric speaker was lower than that of the general speaker for endocrine functions. However, nothing has yet been demonstrated about the effects of the shorter distance than 2.6 m between parametric speakers and the human body. Therefore, we investigated the distance effect on endocrinological function and subjective evaluation. Nine male subjects participated in this study. They completed three consecutive sessions: a 20-min quiet period as a baseline, a 30-min mental task period with general speakers or parametric speakers, and a 20-min recovery period. We measured salivary cortisol and chromogranin A (CgA) concentrations. Furthermore, subjects took the Kwansei-gakuin Sleepiness Scale (KSS) test before and after the task and also a sound quality evaluation test after it. Four experiments, one with a speaker condition (general speaker and parametric speaker), the other with a distance condition (0.3 m and 1.0 m), were conducted, respectively, at the same time of day on separate days. We used three-way repeated measures ANOVA (speaker factor × distance factor × time factor) to examine the effects of the parametric speaker. We found that the endocrinological functions were not significantly different between the speaker condition and the distance condition. The results also showed that the physiological burdens increased with progress in time independent of the speaker condition and distance condition. © 2011 Act Nerv Super Rediviva.

The objective of this study is to examine the influence of head cooling on human psychological and physiological responses during long-time bathing, and to evaluate whether fanning or a water pillow is more suitable for head cooling. In reference to the results, the scores of thermal comfort were improved by fanning at 20, 25, 30℃, and a significant difference was recognized in comparison with the control. In addition, head cooling maintained the thermal comfort for a longer time by inhibiting a rise of the oral temperature, skin temperature of the cooling parts and the non-immersed parts, and sweating. Therefore, we demonstrated that fanning to the face is the most suitable method to achieve head cooling while bathing.

The prediction method of melatonin suppression values was based on previous studies related to melatonin suppression and pupil constriction. Estimated values that considered pupil constriction were larger than the actual suppression values. We focused on the pupil constriction and its correction factor to interpret the action spectrum for the properties of the melatonin suppression model. When the correction factor was used to modify the model, actual suppression values were almost completely predictable. These factors suggest that it might be possible to explain the indescribable results.

In recent years, parametric speakers have been used in various circumstances. However, nothing has yet been demonstrated about the safety of parametric speakers for the human body. Therefore, we studied their effects on physiological functions. Nine male subjects participated in this study. They completed three consecutive sessions: a 20-min quiet period as a baseline, a 45-min mental task period with a general speaker or a parametric speaker, and a 20-min recovery period. We measured electrocardiogram (ECG), photoplethysmogram (PTG), electroencephalogram (EEG), blood pressure (BP), and baroreflex sensitivity (BRS). Two experiments, one with a general speaker (the general condition), the other with a parametric speaker (the parametric condition), were conducted at the same time of day on separate days. To examine the effects of the parametric speaker, a two-way repeated measures ANOVA (speaker factor and time factor) was conducted. We found that sympathetic nervous activity and second derivative of PTG in task period and recovery period during the parametric condition were significantly lower than those indications during the general condition. Furthermore, Delta parasympathetic nervous activity during the parametric condition in task period and recovery period tended to be smaller than that during the general condition. The results suggested that the burden of the parametric speaker is lower than that of the general speaker for physiological functions, especially those of the cardiovascular system. Furthermore, we verified that the reaction time with the parametric speaker is shorter than that with the general speaker. J Physiol Anthropol 30(1): 9-14, 2011 http://www.jstage.jst.go.jp/browse/jpa2 [DOI: 10.2114/jpa2.30.9]

OBJECTIVE: Recently, a parametric speaker system has been developed. However, the safety of the parametric speaker for the human body has not yet been demonstrated. Therefore, we studied the effects of parametric speaker sound on salivary hormones and carried out a subjective evaluation. METHODS: Nine male subjects participated in this study. They completed three consecutive sessions: a 20-min quiet period as a baseline, a 45-min mental task period with either a general or parametric speaker, and a 20-min recovery period. The subjects were evaluated by the salivary cortisol and chromogranin A (CgA) concentrations. In addition, they took the Kwansei-Gakuin sleepiness scale (KSS) test before and after the task and also a sound quality evaluation test after it. Two experiments, one with a general speaker (general condition) and the other with a parametric speaker (parametric condition), were conducted at the same time of day on separate days. To examine the effects of the parametric speaker, a two-way repeated measures ANOVA (speaker factor and time factor) was conducted. RESULTS: The results showed that the cortisol concentration was significantly lower during the parametric condition than during the general condition. Furthermore, the sound quality evaluation found a "warm" sensation during the parametric condition to be lower than that during the general condition. A "noisy" sensation during the parametric condition tended to be higher than during the general speaker. However, the CgA concentration and the KSS score were not significantly different for either the speaker factor or the time factor. CONCLUSION: The results suggested that the burden of the parametric speaker was smaller than that of general speaker, especially on the HPA-axis in the endocrine system.

Objective: Recently, a parametric speaker system has been developed. However, the safety of the parametric speaker for the human body has not yet been demonstrated. Therefore, we studied the effects of parametric speaker sound on salivary hormones and carried out a subjective evaluation. Methods: Nine male subjects participated in this study. They completed three consecutive sessions: a 20-min quiet period as a baseline, a 45-min mental task period with either a general or parametric speaker, and a 20-min recovery period. The subjects were evaluated by the salivary cortisol and chromogranin A (CgA) concentrations. In addition, they took the Kwansei-Gakuin sleepiness scale (KSS) test before and after the task and also a sound quality evaluation test after it. Two experiments, one with a general speaker (general condition) and the other with a parametric speaker (parametric condition), were conducted at the same time of day on separate days. To examine the effects of the parametric speaker, a two-way repeated measures ANOVA (speaker factor and time factor) was conducted. Results: The results showed that the cortisol concentration was significantly lower during the parametric condition than during the general condition. Furthermore, the sound quality evaluation found a "warm" sensation during the parametric condition to be lower than that during the general condition. A "noisy" sensation during the parametric condition tended to be higher than during the general speaker. However, the CgA concentration and the KSS score were not significantly different for either the speaker factor or the time factor. Conclusion: The results suggested that the burden of the parametric speaker was smaller than that of general speaker, especially on the HPA-axis in the endocrine system. © 2010 Act Nerv Super Rediviva.

The prediction method of melatonin suppression values was based on previous studies related to melatonin suppression and pupil constriction. Estimated values that considered pupil constriction were larger than the actual suppression values. We focused on the pupil constriction and its correction factor to interpret the action spectrum for the properties of the melatonin suppression model. When the correction factor was used to modify the model, actual suppression values were almost completely predictable. These factors suggest that it might be possible to explain the indescribable results.

This study aimed to investigate the relationship between the muscular strength of the lower extremity in a load side and the characteristics of center of foot pressure (COP) during landing after crossover stepping in the elderly. The study population comprised 8 elderly subjects (average age, 75.8+/-8.0 years) and 9 young individuals (average age, 21.6+/-2.5 years). Using a separation-type force plate, we measured the deflection characteristics of the COP; these were defined by the root mean square of positional change (COP-RMS) and the deflection velocity of the COP (COP-Vel) during landing after crossover stepping. Furthermore, we measured the muscular strength of the lower extremity by using a hand-held dynamometer. By using multiple regression analysis, we detected the calculated muscular strength as the independent variable of the deflection characteristics of the COP. Compared to the young group the elderly group showed significantly higher anterior-posterior COP-RMS values (p<0.05) and lower lateral COP-Vel values (p<0.001). In the elderly, the muscular strengths of the tibialis anterior and adductor magnus were detected as a significant independent variable of the anterior-posterior COP-RMS (R(2)=0.85, R(2)=0.76, p<0.01) and lateral COP-Vel (R(2)=0.75, R(2)=0.65, p<0.05), respectively. With regard to the COP deflection characteristics during landing after crossover stepping in the elderly, we recognized the diagnostic character of the anterior-posterior COP-RMS and lateral COP-Vel. Furthermore, it was suggested that the muscular strengths of the tibialis anterior and adductor magnus played a role in regulating the COP deflection characteristics.

The present study evaluates the potential mitigation of physical workload when using strap support for a portable device. The experiments were designed as consecutive sessions over a 2-h period. Electromyogram signals were recorded from four muscles of six subjects. The perceived level of fatigue on the whole body as well as in the shoulder, arm, lower back and legs was assessed using Borg&apos;s CR-10 scale. All subjects were tested under eight experimental conditions. Results indicated that the biceps brachii muscle displayed significantly lower activity with strap support than without a strap. In the experiments with and without a strap, different levels of force were imposed on the various muscles, which caused changes in the distribution of the physical load. Although the role of the strap might seem evident, using strap support did not always decrease the sensation of fatigue. However, for short-term tasks, using a strap may be recommended.

Light elicits non-visual effects on a wide range of biological functions and behavior. These effects are mediated by a melanopsin-based photoreceptor system that is very sensitive to blue light (440-480 nm) relative to the three-cone visual photopic system. The aim of the current study was to assess the time-of-day-dependent effects of two different wavelength monochromatic lights at 458 nm and 550 nm on human cognitive function. We conducted an experiment in the daytime and nighttime on different days. Twelve subjects were selected, none of whom was either morning-type or eveningtype, as assessed by a translated version of the morningness/ eveningness questionnaire. The cognitive function was measured by event-related potential (ERP) using an oddball task, and arousal level was measured by the Alpha Attenuation Test (AAT). We found that 458 nm light exposure caused a significantly larger P300 amplitude than occurred with 550 nm light. There was a significant interaction among wavelength, time of day, and electrode site. Exposure to 458 nm light induced a larger P300 amplitude at nighttime than in the daytime at the Fz electrode site. The Alpha Attenuation Coefficient (AAC) at nighttime was higher than in the daytime. Our results suggest that short wavelength monochromatic light can affect the circadian rhythms of cognitive functions, and indicate that these effects are mediated by a melanopsin-based photoreceptor system. This study has extended previous findings in terms of time of day, and higher cognitive function by using an endogenous ERP component, P300.

We examined the effects of eating a meal on the physiological responses during the performance of a mental task. Ten male subjects (25±4.5 years) participated in this study. We measured the following items: electrocardiogram (ECG), photoplethysmogram (PTG), baroreflex sensitivity (BRS), salivary-amylase activity levels, NASA task load index (NASA-TLX), reaction time and correct rate of the mental task. All experiments were conducted at the same time of day on separate days under two lunchtime conditions, which were taking a meal (meal condition) and not taking a meal (no meal condition) during the lunchtime. The mental tasks were performed before and after the lunchtime. We analyzed the collected data using a paired t-test. The task performance and subjective evaluation (NASA-TLX) showed no significant difference between meal and no meal conditions. On the other hand, heart rate, pulse wave transit time and BRS were significantly different between meal and no meal conditions. The heart rate during the meal condition was significantly (p<0.01) higher than that during the no meal condition. Pulse wave transit time and BRS during the meal condition were significantly lower than those during the no meal condition. The results suggested that eating a meal effectively increases activity level of physiological functions during the performance of a mental task, especially in the cardiovascular system.

The effects of various heel elevations on postural adjustment and lower-extremity muscle activity during the squat-to-stand (SQ-ST) movement were investigated. Eight healthy mate subjects participated in the experiment, which involved rising from a deep squat with three different heel elevations: a full squat (FS), in which the plantar aspects of the feet were in full contact with the floor (0 degree), slope squat (SS), in which a 15-degree wedge was applied underneath the foot, and tiptoe squat (TS), in which subjects lifted their heels to their preferred height by extending the metatarsophalangeal joint. Electromyograms were taken of the extensor digitorum brevis (EDB), tibialis anterior (TA), rectus femoris (RF), and gastrocnemius (G) muscles. The results showed that heel elevation significantly affected the postural adjustment: TS caused significantly smaller anterior displacement in the knee and the hip during ankle dorsiflexion and minimized the duration of the forward movement required to stand. On the other hand, EDB activity strongly increased in TS. However, use of foot slope appeared to decrease activities of RF, TA, and EDB. These findings suggest that the use of a foot slope to achieve a squat-to-stand movement may be appropriate to assist patients with weak lower-extremity muscles.

Deep squatting places a burden on the lower limb muscles and influences postural balance. We attempted to determine the effects of postural changes on the rectus femoris, tibialis anterior, gastrocnemius, soleus, and extensor digitorum brevis muscles during squatting in 8 healthy male subjects. Three squatting conditions were involved: full squatting (FS), tiptoe squatting (TT), and tiptoe squatting on a 15° slope (TTS), performed randomly and recorded in a period of 4 min for each task. The influence of the squatting condition on electromyography and vertical ground reaction force parameters was examined in order to observe the effect of postural alteration on muscle activity and balance control. The results showed that the change of squatting posture from FS to TT decreased the activity of the rectus femoris and tibialis anterior muscles. FS has been suspected as a main cause of musculoskeletal complaint during prolonged squatting. In contrast, as the heel was lifted, the extensor digitorum brevis muscle increased to 39% of maximum activation. On the other hand, sway analysis at TT showed balance instability regarding the large area occupation of the center of pressure displacement. The presence of a 15° slope significantly reduced the muscular load. This simple study suggests that the inclusion of a sloping surface in daily activities that requires a squatting posture would be an effective means to reduce muscular load.

The purpose of this study was to investigate the influence of force tremor (FT) on the mechanomyogram (MMG) recorded by a condenser microphone (MIC) and an accelerometer (ACC) for the measurement of agonist and antagonist muscles during submaximal isometric contractions. Following determination of the isometric maximum voluntary contraction (MVC), 10 male subjects were asked to perform elbow flexion and extension at 20%, 40%, 60%, and 80% MVC. Surface electromyogram (EMG) and MMG of the biceps brachii (BB) and triceps brachii (TB) were recorded simultaneously using a MIC (MMG-mic) and an ACC (MMG-acc). We analyzed the root mean square (RMS) for all signals and compared the sum of the power spectrum amplitude (SPA) at 3-6 Hz and 8-12 Hz between the MMG-mic and the MMG-acc. During elbow flexion and extension, the RMS of the EMG and the MMG-mic of the agonist were significantly (p&lt 0.05) higher than those of the antagonist in each contraction level. The RMS of the MMG-acc of the antagonist showed no significant (p&lt 0.05) difference from that of the agonist, or tended to be higher than the agonist. The SPA of the MMG-mic of the agonist at 3-6 Hz and 8-12 Hz tended to be higher than the antagonist in elbow flexion and extension at each contraction level. The SPA of the MMG-acc of the agonist and that of the antagonist showed no significant (p&lt 0.05) difference, or the antagonist MMG-acc tended to be higher than that of the agonist. These results suggest the MMG detected by a MIC appears to be less affected by FT than is the ACC because of its inherent characteristic to reduce FT in simultaneously evaluated agonist and antagonist muscles by means of MMG during submaximal isometric contraction.

The purpose of this study was to investigate the influence of the force tremor (FT) on mechanomyographic (MMG) signals recorded by a condenser microphone (MIC) and an accelerometer (ACC) during measurement of agonist and antagonist muscles in sustained isometric contractions. Surface electromyographic (EMG) signals and MMG signals by MIC (MMG-MIC) and ACC (MMG-ACC) were recorded simultaneously on biceps brachii (BB) and triceps brachii (TB). Following determination of the isometric maximum voluntary contraction (MVC), 10 male subjects were asked to perform sustained elbow flexion and extension contractions at 30% MVC until exhaustion. We analyzed the root mean square (RMS) for all signals and compared the sum of the power spectrum (SPA) for 3-6 Hz and 8-12 Hz and the ratio of the sum of SPA for 3-6 Hz and 8-12 Hz in SPA for 3-100 Hz (SPA-FT/SPA- 3-100Hz) between MMG-MIC and MMG-ACC. During all sustained muscle contractions, the RMS of EMG and MMG-MIC was significantly (p&lt 0.05) increased in antagonistic muscle pairs, while the increase was more noticeable for the agonist than for the antagonist. In addition, the antagonist had a significantly (p&lt 0.05) smaller amplitude than the agonist muscle. The RMS of MMG-ACC, however, showed no significant (p&gt .05) difference in RMS amplitude and slope between agonist and antagonist muscles during flexion. In extension, the MMG-ACC-RMS amplitude showed a tendency to be higher in the antagonist than in the agonist, while their slopes showed no significant (p&gt 0.05) difference. The SPA for 3-6 Hz and 8-12 Hz in MMG-MIC showed a tendency to be higher in the agonist than the antagonist, and the slopes of the agonist were significantly (p&lt 0.05) higher than those of the antagonist in all contractions. In MMG-ACC, SPA and slopes for 3-6 Hz and 8-12 Hz tended not to differ between agonist and antagonist. The SPA-FT/SPA-3-100Hz in MMG-ACC showed that the antagonist was higher than that of the agonist in all contractions. The MMG-MIC however, showed a tendency toward no difference between the agonist and antagonist. In the assessment of muscle activity during simultaneous measurement of the agonist and antagonist during sustained muscle contractions, the MMG signal detected by MIC appeared to be less affected by FT than by ACC due to the different inherent characteristics of the two transducers.

A specially designed mental task was performed by 16 subjects for frequency domain analysis of skin conductance (SC) to evaluate mental workload. The task was to memorize target letters, detect them within a 4x4 alphabet arrangement, and answer whether the number of targets contained in the arrangement corresponded to a randomly displayed number. As the number of target letters increased, the score for the card-sort NASA Task Load Index (CSTLX) and task performance increased significantly. The traditional parameter for the number of transient wave forms of SC response (SCR) and the height of its wave did not show any significant effect of task difficulty. In addition, SCRs were subjected to Fourier transformation and integration of the spectrum from 0.03 to 0.5 Hz. This frequency domain analysis enabled detection of small differences in mental workload that could not be detected by traditional amplitude domain analysis. Frequency-based analysis enables easy processing of physiological signals and is very effective in evaluating mental stress using SC recorded under actual environmental conditions such as the driving of a vehicle.

The influences of monochromatic light were studied through measurement of EEG (Fz, Cz, Pz), ECG, blood pressure, pupil diameter, oral temperature, and subjective evaluation. The experiment employed ten young males (23±2.9yrs) with normal color perception. Three monochromatic light conditions were transmitted through three types of filter to produce three different wavelenghts (458 nm, 550 nm, 670 nm). The main effect of monochromatic light and the exposure time on EEG in Fz and Pz was significant. The alpha wave ratio was apparently lower in the 458-nm wavelength than in the other wavelengths (550 nm, 670 nm). The interaction between the light condition and the time was significant in pupil diameter. At 11 minutes of light exposure, pupil diameter in the 458-nm and the 550-nm wavelength light was obviously smaller than that in the 670-nm wavelength light. Moreover, at 19 minutes of exposure, pupil diameter in the 458-nm and the 550-nm wavelength light was significantly smaller than that in the 670-nm wavelength light. In conclusion, we estimated that arousal level increased during the exposure to 458-nm wavelength light. The effect of 458-nm wavelength light on the arousal level and pupillary reaction might be similar to the spectral sensitivity based on melatonin suppression described in recent studies. Therefore, this finding may support recent understanding of a non-visual system including the intrinsic photosensitive retinal ganglion cell (ipRGC).

To design an ergonomically user-friendly video camera, electromyograms (EMGs) at six muscle locations were measured to find an optimal grip angle. Grip angle is an important factor in the usability of general consumer electronic products. The results indicated that vertically-gripped cameras, where the grip angle is large from the axis of the lens alignment, reduced muscular load. Particularly a grip angle from 105 degrees to 135 degrees produced little fatigue. In consideration or our results, we developed a compact and lightweight video camera with a grip angle of 105 degrees based on ergonomic methodology.

Modern manufacturing and design should satisfy not only the requirements of high cost performance but also of the user. Besides that, the social environment which surrounds manufacturing is rapidly changing depending on new technologies. To create future products with user satisfaction, the effective use of human physiological data is essential. This is where knowledge of physiological anthropology can be applied. Physiological anthropologists have been pointing out a limit to the interpretation of the physiological data based on its average value. They have begun to notice that the physiological functions of humans show various types according to the blended effect of heredity and the surroundings. Adequate consideration of physiological polymorphism is indispensable to accomplish manufacturing that is well devised for human. In this study the concept of manufacturing and design based on physiological polymorphism is expressed. The target and the methodology for new manufacturing are discussed in seven fields, that is, welfare equipment, clothes, artificial tissue, sporting gear, furniture, building materials, and human interface. Through the above discussion, a procedure to achieve manufacturing and design based on physiological polymorphism is proposed.

Work requiring extremely body flexion is strongly associated with a high incidence of musculoskeletal injuries often reported during adopting squatting. In this study, the influence of different lower seat heights on the muscular stress in squatting on a stool (SS) were examined in comparison with fully squatting (FS). Fourteen healthy Indonesian males were recruited in the experiment. Two-dimensional body kinematics, ground reaction force (GRF) and electromyography (EMG) data were collected as subjects performed forward movement under four squatting height conditions which were FS and SS at 10 cm, 15 cm and 20 cm seat height. The results demonstrated that the change from FS to SS primarily affected the segmental angular flexions and muscular activities in the upper and lower limbs. GRF data showed that the SS conditions delivered 24% body weight onto the seat. The change of FS to SS showed significantly decrease in muscular load of the rectus femoris and tibialis anterior. In contrast, the soleus and gastrocnemius increased the activities as the seat height increased. The type of task that required the hand to handle the object on the ground level affected the trunk to be more flexed as the seat height increased. The findings of this study suggest that the use of a lower seat stool of a proper height seems to be a sub-optimal solution considering the change of muscular load associated with the discomfort in a squatting posture.

By estimating the deflection velocity from the center of foot pressure (COP), this study aims to prove that the characteristics of the backward stepping reaction in the elderly are related to the strength of the antigravity muscles. The participants in this study were 10 elderly (average age 75.6+/-7.6 years) and 13 young (average age 22.0+/-2.6 years) subjects. Using force plate analysis, we measured the shift in the deflection velocity (V-RMS) and the maximum deflection velocity (V-MAX) from the beginning of the COP movement to the onset of the stepping reaction. Furthermore, we measured the strength of the antigravity muscles using a hand-held dynamometer. We correlated the V-RMS, V-MAX, and the rate of change of the deflection velocity (MAX/RMS) with muscular strength. When compared with the young subjects, the elderly showed significantly lower values of V-RMS (p<0.05) and significantly higher values of MAX/RMS (p<0.01). Furthermore, when compared with the young subjects, the elderly showed significantly lower values of muscular strength for all muscles studied (p<0.001). We established a significant correlation between the V-RMS, MAX/RMS, and muscular strength by carrying out a regression analysis (V-RMS: gluteus maximus (r=0.50, p<0.05) and rectus abdominis (r=0.48, p<0.05); MAX/RMS: adductor magnus (r=-0.66, p<0.001) and flexor digitorum longus (r=-0.62, p<0.01)). Differences were observed in the V-RMS and MAX/RMS during the backward stepping reaction; it was proposed that these differences were related to the age and muscular strength of the subjects. Therefore, further investigations should be undertaken in order to understand the effects of aging on the stepping reaction. In other words, the change-in-support strategy, including the preparatory phase of the stepping reaction, and its relationship with muscular strength should be further investigated.

The purpose of this study was to compare the cardiovascular responses to different types of mental stress. Ten healthy males performed a mental arithmetic task (MA) on one day and were exposed to white noise (WN, 80dB) on another day. Both the MA and the WN were composed of four 5-min consecutive periods with a 3-min rest between them. On each day, the systolic and diastolic blood pressure (SBP and DBP), mean arterial pressure (MAP), cardiac output (CO), and total peripheral resistance (TPR) were measured continually during the entire experimental period. The changes from the baseline (Δ) in all periods were calculated for both mental stresses. As for the results, the δMAP, δCO, δHR, and δTPR in the MA did not significantly change during the task periods. However, in the WN, the δMAP and δTPR showed significant increases over the time of the consecutive periods. In addition, we discuss the response patterns for the two mental stresses. We examine three hemodynamic reactivity patterns: a cardiac pattern characterized by increased CO and decreased TPR, a mixed pattern characterized by a moderate increase in both CO and TPR, and a vascular pattern characterized by increased TPR and decreased CO. The results show that throughout all task/exposure periods, the response pattern remained the same for six subjects in each stress. Furthermore, of these six subjects, half showed the same response pattern in both the MA and the WN. In conclusion, compared to the MA task, consecutive WN exposure showed an accumulation of stress responses. A change in TPR contributed to a gradual increase in MAP in the WN. It is also possible that among the subjects there were different types of response to the MA and WN.

We examined the effects of monochromatic light on the time sense and the central nervous system. Nine young adult volunteers participated in this study. They were exposed to red-light and blue-light environments (illuminance was kept at 3101x). We evaluated the time sense by time-production tests of 90s and 180s and measured the P300 event-related potentials during an auditory oddball task. The 90-s time intervals produced by subjects in the two monochromatic light conditions were not significantly different. However, the 180-s time interval produced in the red-light condition (163.2±50.4s) was significantly (p&lt 0.05) shorter than that in the blue-light condition (199.0±54.4s). The peak latency of P300 in the red light (322.2±26.6ms) was found to be significantly (p&lt 0.05) shorter also than that in the blue light (332.6±20.2ms). The feelings measured by the visual analogue scales in the two light conditions were not significantly different. These results indicate that the time sense ran faster in the red-light than in the blue-light condition. We suggest that the higher activity in the central nervous system that is accounted for by the shorter latency of P300 is related to the acceleration of the time sense.

The present study investigated the circulatory responses to two mental tasks. Forty males and females performed a mental subtraction task and a color-word task. During each task, the systolic and diastolic blood pressure, mean arterial pressure, heart rate, stroke volume, cardiac output, and total peripheral resistance were measured as cardiovascular indices for a 5-min baseline, a 5-min task period, and a 10-min recovery period. As for the results, three hemodynamic reactivity patterns were verified: Pattern C, characterized by increased cardiac output and decreased total peripheral resistance Pattern M, characterized by a moderate increase in both cardiac output and total peripheral resistance and Pattern V, characterized by increased total peripheral resistance and decreased cardiac output. Also, four response types were found among all subjects: Type 1: cardiovascular responses showed the cardiac pattern for both tasks Type 2: cardiovascular responses changed between the cardiac pattern and the mixed pattern with a change of tasks Type 3: cardiovascular responses showed the mixed pattern for both tasks Type 4: cardiovascular responses changed between the mixed pattern and the vascular pattern with a change of tasks. The comparison between types showed that Type 3 and Type 4 had an elevation in their blood pressure by an increased total peripheral resistance. On the other hand, Type 1 and Type 2 tended to have an increased blood pressure by a rise in their cardiac output. And Type 3 and Type 4 showed higher blood pressure and higher scores on the Type A behavior pattern questionnaire. In conclusion, at least four types of circulation response to the mental tasks existed, with Type 3 and Type 4 having higher blood pressure responses and tending to have an elevated blood pressure bv a rise in their total peripheral resistance.

This study was designed to investigate the physiological effects of color in terms of blood pressure and the results of electroencephalogram (EEG) as subjects looked at the sheets of paper of various colors. A questionnaire was also used to assess psychological effects. Three colors (red, green, blue) were shown to each subject in randomized order. The various colors showed distinctly different effects on the mean power of the alpha band, theta band, and on the total power in the theta-beta EEG bandwidth and alpha attenuation coefficient (AAC). Scores of the subjective evaluations concerning heavy, excited, and warm feelings also indicated significant differences between red and blue conditions. Against to our prediction, blue elicited stronger arousal than did red as expressed by the results of AAC and the mean power of the alpha band, which conflicted with the results of the subjective evaluations scores. This phenomenon might be caused by bluish light's biological activating effect. The powers of the alpha band, and the theta band, and the total power of the theta-beta bandwidth as measured by EEG showed larger values while the subjects looked at red paper than while they looked at blue paper. This indicated that red possibly elicited an anxiety state and therefore caused a higher level of brain activity in the areas of perception and attention than did the color blue. Red paper's effect to activate the central cortical region with regard to perception and attention was considerably more distinguishable than was the biological activating effect of bluish light in our study.

【目的】急速な高齢化に直面している我が国においては，重篤な合併症を引き起こす高齢者の転倒の予防・防止対策が急務となっている。高齢者の転倒予防には補償的バランス反応であるステッピング反応が重要と考えられる。本研究の目的は，後方向へのステッピング反応における，足圧中心の加速度とその制御に関わる筋力との関係について，若年者と比較した場合の高齢者の特性を明らかにすることである。<BR>【方法】対象は健常高齢者10名(平均年齢76.3±7.6歳)，対照群として健常学生14名(平均年齢21.9±2.6歳)を選定した。全ての被験者には口頭および紙面にて実験の趣旨を説明し，同意を得た後に計測を行った。被検者には左右分離式フォースプレート(Anima製G-6100)上で両足をそれぞれ別のプレートに位置させ，静止立位を20秒間保持させた。その後，検者の合図に従って，後方向へ重心を最大限移動し，片脚を後方へステップさせる課題動作をおこなった。課題動作中の足圧中心動揺をサンプリング周波数200Hzにて記録した。さらに被検者の筋力(腹筋群，腸腰筋，大殿筋，股内転筋群，大腿四頭筋，ハムストリングス，前脛骨筋，下腿三頭筋，長腓骨筋，後脛骨筋，足趾屈筋群)を携帯用徒手筋力計(HOGGAN HELTH INDUSTRY製 MICROFET)を用いて計測した。データ処理は，ステップ(フォースプレートから足が離れる)直前の足圧中心の側方向(L)と後方向(B)加速度値の合成成分(=√(L²+B²))を算出した。筋力は各被験者の体重で除した値(体重比筋力)を求めた。統計処理は合成加速度と筋力における若年群と高齢群の比較にWelchのt検定を用いた。さらに合成加速度と筋力との関係を知るために，合成加速度を目的変数，各筋力を説明変数として，棄却F値2.0でステップワイズ法による重回帰分析を行った。<BR>【結果】若年群と高齢群間で合成加速度値に有意な差は認めなかった。体重比筋力は全ての筋力において，若年群に比し高齢群が有意に低値を示した。合成加速度と筋力との関係は，重回帰分析の結果，合成加速度の有意な説明変数として，高齢群では長腓骨筋力と腸腰筋力が検出され(R=0.99，R²=0.98，p<0.01，r=-0.57)，若年群では中殿筋力が検出された(R=0.62，R²=0.38，p<0.05，r=-0.62)。<BR>【考察】本研究では，ステップ動作において力学的に不安定性が増加する足部の離床直前の足圧中心加速度を指標とした。重回帰分析の結果から，若年群の側後方向の加速度(不安定性)には骨盤帯の側方安定性の作用を有する中殿筋の筋力が関与していることが示唆された。高齢群では，足関節の外側安定性の作用を有する長腓骨筋の筋力および体幹部と大腿部を連結する腸腰筋の筋力の関与が示唆された。さらに，これら両群における違いは，後方へのステップ動作に用いる姿勢方略の違いが影響していると思われ，今後併せて調査していく必要性があろう。<BR>

The ultimate aim of this study is to develop a quantitative and objective method for designing toothbrush handles for ease-of-grip by means of ergonomic procedures. It is reasonable to think that easy-to-grip handles would enable more effective removal of dental plaque. To this end, the present study considered a hypothesis that the upper and lower part of the handle would have different roles, and have different optimum diameters depending on the human hand sizes when the handle is palm-gripped. To examine the hypothesis, 24 test toothbrushes were prepared combining a cylindrical upper part of 4 different diameters with a cylindrical lower part of 6 different diameters. Eighteen subjects were divided into 3 groups by their hand sizes. Electromyogram (EMG) of 5 muscles in forearms and hands of the subjects were measured when brushing. The handle diameter which gave minimum muscle load (MML) was calculated by the quadratic regression analyses of the EMG data. The analysis has demonstrated that the diameters with MML for each handle part have been obtained depending on the hand size. In conclusion, our hypothesis was appropriate and this study has shown that ergonomic procedures by EMG measurements are potential tools for designing toothbrushes for ease-of-grip.

An electrogastrogram (EGG) is considered to be an index to the autonomic nervous system of the digestive organs. In the present study, we attempted to clarify whether or not an EGG can be used to evaluate the influence of illumination, and what kinds of effect taste stimuli and illumination have on the autonomic nervous system. In this study, we used the ratio of the normal wave component of the EGG (EGG-NR: 2-4.5 cpm power/1-10 cpm power) and the amplitude of a normal wave (EGG-M: integrated EGG of 2-4.5 cpm). Thirteen healthy males participated in 16 experimental conditions (4 lighting conditions×4 taste stimuli). The four lighting conditions were set by combinations of illuminance levels of 200 and 1500 lx and color temperatures of 3000 and 7500 K. The four taste stimuli were sweet (glucose), salty (salt), sour (acetic acid), and bitter (quinine). The changes in EGG-NR and EGG-NI were compared for different taste conditions. The results showed that EGG-NI was not significantly affected by the different taste conditions. However, the main effect of taste on EGG-NR was significant: sweet and salty tastes were significantly higher than the bitter taste. EGG-NR and EGG-NI in different lighting conditions were also compared. The main effect of different color temperatures was also significant, but the illuminance level did not affect EGG-NR. EGG-NR increased significantly at the lower color temperature. On the other hand, EGG-NI significantly increased at the lower illuminance. These results suggest that parasympathetic nervous activity has a predominant effect on gastric activity in different lighting environments. Therefore, EGG measurements may be useful indicators for illumination environment studies.

本研究では身体に生じる加速度値から得られるゼロクロスポイント（ZCP）数を指標とし，高齢者の動的バランス評価における加速度計の有用性を検討した。対象はクロスオーバーステップ動作が可能な健常高齢者9名と健常若年者11名とした。分離型Force plateの床反力値から，ステップ動作における静止立位期と片脚立位期を区分し，各期の動揺量とZCP数について高齢群と若年群で比較した。結果，片脚立位期のZCPでは若年群に比較し高齢群で有意に低値を示した（p＜0.01）。結論として，本研究で用いたZCP数を指標とすることで，動的バランスにおける高齢者の姿勢調節の特性をより詳細に評価できる可能性が示唆された。<br>

Indonesians commonly perform activities on the floor that require squatting postures. It has been identified that adopting squatting postures without any proper support would gradually cause postural stress. This study examines the influence of different squatting heights to the body kinematics and subjective discomfort rating. The subjects were divided into two different body types: overweight subjects with BMI>24.9 and normal weight subjects with BMI 18-24.9. The subjects adopted a squatting posture at no-stool condition and at the stool height of 10, 15, and 20 cm. The task was to simulate the work close to the ground level with the hip joint deeply flexed. Body segmental angular flexion (SAF) and the visual analog scale (VAS) method were selected for parameter analyses. Significant differences were found in both parameters SAF (trunk, hip, knee, and ankle) and VAS. The interaction effect was found by squatting height and the body type for SAF of the trunk (p<0.05). However, the increasing BMI index was also found significantly affected associated with the anthropometrical characteristics for buttock height and lower limbs depth. It is suggested that normal weight subjects sit comfortably at 15 cm stool height, whereas overweight subjects preferred 20 cm stool height as a better acceptability condition in terms of overall parameter analyses.

This study was designed to investigate the physiological effects of color by contingent negative variation (CNV) while looking at color cloth. Profile of Mood States (POMS) was also used to declare the psychological effects. Five stimuli colors (red, yellow, green, purple, blue), and black color as reference were shown to every subject in randomized orders. The results showed that, color effect on the late component of CNV was significant, red and green elicited significantly higher values than blue. The tension-anxiety (T-A) score of POMS also strongly showed significant differences with respect to color stimuli, while green and blue were lower than red. The correlation coefficient between POMS scores and relative values of late CNV component in terms of the ratio of each color to black reference showed that the T-A score appeared to mostly have a positive correlation with the late CNV component. In conclusion, the opposite physiological and psychological effects between red and blue cloths were confirmed, and the green cloth affected people physiologically in a similar way to the red cloth, meanwhile it affected people psychologically in the way of the blue cloth in this study.

This study was intended to determine the effects of continuous bright light exposure on cardiovascular responses, particularly heart rate variability (HRV), at rest and during performance of mental tasks with acute nocturnal sleep deprivation. Eight healthy male subjects stayed awake from 21.00 to 04.30 hours under bright (BL, 2800 lux) or dim (DL, 120 lux) light conditions. During sleep deprivation, mental tasks (Stroop color-word conflict test: CWT) were performed for 15 min each hour. Blood pressure, electrocardiogram, respiratory rate, urinary melatonin concentrations and rectal temperature were measured. During sleep deprivation, BL exposure depressed melatonin secretion in comparison to DL conditions. During sleep deprivation, exposure to BL delayed the decline in heart rate (HR) for 4h in resting periods. A significant increment of HR induced by each CWT was detected, especially at 03.00 h and later, under DL conditions only. In addition, at 04.00 h, an index of sympathetic activity and sympatho-vagal balance on HRV during CWT increased significantly under DL conditions. Li contrast, an index of parasympathetic activity during CWT decreased significantly under DL conditions. However, the indexes of HRV during CWT did not change throughout sleep deprivation under BL conditions. Our results suggest that BL exposure not only delays the nocturnal decrease in HR at rest but also maintains HR and balance of cardiac autonomic modulation to mental tasks dnring nocturnal sleep deprivation.

In a system in which the operator must accomplish two or more tasks at the same time, an example of a method for preventing a serious accident would be sounding an alarm and giving a visual cue simultaneously. However, errors can come from inside or outside a system that might cause an alarm to fail. If this occurs, the operator may come to doubt or distrust the safety system, and its effectiveness is ruined. This can be very stressful for the operator's mental workload. In this study, we examined the influence of the absence of an alarm sound following some use of the system at 100% accuracy during performance of a cognitive task. We also examined the influence of the absence of the alarm as measured by EEG, HRV, and other tests as an index of mental workload. We used the difference in warning presentation rate as a way of measuring the influence on performance. The performance was the worst and the sympathetic nerve activity was highest in the 50% warning presentation rate condition, and the performance was better for where warning was not presented (0%) or at all of the presentation without fail (100%), and the relation between the warning presentation rate and the task performance showed the tendency to a reverse-u-shaped. It was suggested by this result that the absence of a warning sound brings about a decrease in a subject's performance and a rise in the operator's mental workload.

The purpose of this study is to prove that the characteristics of the stepping reaction from the center of foot pressure (CFP) deflection toward the lateral direction in the elderly are related to muscular strength. Nine elderly people and eleven young students participated in this study. A subject stepped toward the lateral direction on a force plate. We measured CFP deflection characteristics of the subjects in the two groups. We measured muscular strength from the trunk to the foot using a hand-held dynamometer. We compared the CFP deflection characteristics between the two age groups. Furthermore, we observed a correlation between the muscular strength and CFP deflection characteristics in the single stance phase, which recognized a pathognomonic difference between the two groups. As compared with the young group, the elderly group showed significantly low values of deflection speed and standard deviation of deflection speed. It was suggested that the antigravity muscle extending from the planta pedis to the trunk contributed to the control of CFP deflection speed in the elderly group. Furthermore, it was suggested that the unsteadiness in the elderly was a result of a decrease in the CFP control ability due to the depression of the feedback mechanism of the sensory system with aging.

This article presents our recent studies on the effects of color temperature on the taste sense and the influence of color temperature on bright light exposure during night rest period. Ten male Japanese and ten male Chinese were exposed to four illumination conditions (200, 1500 lx X 3000, 7500 K). Their taste threshold of four common tastes and amount of saliva were measured. It was found in both Japanese and Chinese subjects that sensitivities to sweet and bitter taste were decreased under the lower illuminance condition. Under the lower color temperature condition, sensitivity to bitter taste in Japanese and sweet taste in Chinese were decreased. Secretion of saliva increased under the lower illuminance condition in both Japanese and Chinese. Only in Chinese subjects, secretion of saliva increased under the lower color temperature condition. In a separate experiment, six male Japanese students were subjected to bright light exposure during a night rest period. They performed a mental task from 23:00 h till 02:00 h, and took a rest from 00:00 h to 01:00 h. During the rest period they were exposed to bright light (3000 lx) of three different color temperatures: 3000 K, 5000 K, and 7000 K. After exposure to bright light of 3000 K but not at other color temperatures, the EEG α1 band ratio and the β band ratio at 02:00 h were higher and lower, respectively, than that at 01:00 h. These findings indicated that lower color temperature bright light exposure during a night rest break led to a reduction of subjects' arousal level during the subsequent work. Herein, we discuss these results from the viewpoint of physiological anthropology.

Interest of human adaptability to city life is one of the most principal topics of physiological anthropology. Especially, cultural adaptation and flowing stresses by itself is the most important viewpoint of human adaptability in the recent modern life. In this paper, the authors reviewed the keywords of physiological anthropology, especially with the focus on techno-adaptability, and presented our experimental trials to study physiological polymorphism of cardio-vascular reactivity to mental stresses. We scoped the psychological stresses by means of mental tasks as an experimental model of techno-stress. Techno-stress was defined as not only from inadequate interface of man-machine system, but also from increased social complexity owing to highly advanced technological social system. In the experimental trial, we observed different types of cardio-vascular responses to several mental tasks. Blood pressure rose significantly during the tasks. However, contribution of change in cardiac output and total peripheral resistance on it was not the same between subgroups of the subjects.

This study measured and analyzed the amount of saliva and the taste threshold in response to lighting conditions (illuminance and color temperature) in different ethnic groups. Ten Japanese and ten Chinese healthy non-smoking male college students participated in the study. According to the results of repeated-measure ANOVA, the effect of illumination on the amount of saliva was significant in the Japanese students, and the Chinese students showed same tendencies regarding their saliva response, but not significant. On the other hand, the effect of illuminance on the taste threshold was considered significant in both these groups. Regarding the effect of color temperature, this study found significant changes in taste threshold only for Chinese. It is interesting to note that significant differences in the taste threshold regarding a salty taste were seen between the subject groups. The results of the present study indicated that the lighting condition could be considered an important parameter of taste sensation.

The present study was conducted to investigate the influence of different lighting condition and taste stimulus on the autonomic nervous system measured by electrogastrogram (EGG). We conducted the experiment for 16-conditions (4 lighting conditions×4 taste solutions). The four lighting conditions were 200 and 1500 lx in illuminance and by 3000 and 7500K in color temperature. The four taste solutions were sweet (glucose), salty (salt), sour (acetic acid), and bitter (quinine). The subjects were healthy seven Japanese and six Chinese males. The changes of EGG normal wave ratio (EGG-NR; 2〜4.5 cpm power/1〜10 cpm power) after stimulation were compared among taste conditions. As a result, the main effect of taste was significant. EGG-NR of the sweet and the salty taste were higher than the bitter taste. Then separate analyses were conducted for Japanese and Chinese. EGG-NR for the sweet taste and the salty taste were higher than the bitter one in Japanese, but there were no difference in Chinese. We also compared EGG-NR in different lighting conditions, the main effect of color temperature was significant, but not in the illuminance. EGG-NR increased significantly in the lower color temperature.

The aim of this study was to examine physiological responses during a mental task as indices of mental workload. Electroencephalogram (EEG), heart rate variability (HRV), brain haemodynamics, and blood pressure (BP) were measured during a visual search task accompanied with short-term memory. When the difficulty of task became greater, the larger changes in beta-1 power ratio of EEG and diastolic BP were observed. Along with work execution, parasympathetic nervous activity decreased. Furthermore, beta-1 power ratio and increase in diastolic BP showed a significant correlation. In conclusion, this study suggests that beta-1 power ratio of EEG and diastolic BP are useful in the evaluation of mental workload as the degree of difficulty, and HRV might be effective to evaluate a time change of a mental workload with accomplishment of the task.