岩永 光一

ADLが自立している高齢者9名と健常学生11名を対象に,側方ステップ動作時の身体動揺量と筋力を測定し群間比較した.その結果,高齢者の側方ステップ動作の特徴として,力学的に不安定な状況に移行するに従い合成重心部でのフィードバックを元とした立ち直りあるいは調節機能が弱くなることが示唆された.また,不安定な状況下において高齢者は骨盤・大腿部の側方安定性に寄与する股外転筋群の機能が低下していることが推測された

Bright light (BL) exposure at night leads to suppressed secretion of melatonin and an attenuated fall in internal temperature at rest from the night to the early morning. However, it is unknown at the present whether typical diurnal variations in reflex responses to thermal challenges are similarly affected by BL exposure at night. We investigated the control of cutaneous vasodilator and sweating responses to hyperthermia in the early morning after artificial BL exposure at night, compare with dim light (DL) exposure. Six subjects stayed awake in a semi-supine position under DL (120 1x) or BL (2800 1x) conditions between 21.00 and 04.30 h. Urine samples were collected at 04.30 h. Beginning at 05.30 h, the lower legs were immersed for 50 min in 42 C water. The subjects remained awake for 21 h until the end of hot water immersion. Urinary 6-sulphatoxymelatonin levels following BL were significantly lower than after DL. Oesophageal temperature (T-es) before heating was significantly higher following BL [36.41 +/- 0.10 (DL) vs. 36.55 +/- 0.09 (BL) degrees C]. The T-es thresholds for the onset of cutaneous vasodilation and sweating were significantly higher with BL than with DL conditions (approximately 0.15 degrees C, respectively). We found that the internal temperature threshold for thermoregulatory control of cutaneous vasodilation and sweating responses to passive heating in the early morning can be modified by the level of light exposure the prior night. Thus both basal internal temperature and the regulation of internal temperature are modified by BL exposure at night.

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.

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.

The methodology of physiological anthropology has been defined in the capacity of an independent academic field by five keywords: environmental adaptability, technological adaptability, physiological polymorphism, whole-body coordination and functional potentiality, clearly suggesting the direction of approach to human beings in the field of physiological anthropology. Recently, these keywords have attracted a great deal of attention from physiological anthropologists in Japan. Physiological anthropology is based on a biological framework. From the viewpoint of biology, it is essential to discuss the biological function of human behavior. In this brief conceptual manuscript, the biological aspects of physiological anthropology are discussed in relation to the five keywords.

The purpose of this study was to clarify the strategy of postural control in frontal plane occurred by lateral shifting of center of gravity, and furthermore to reveal related factors of postural strategy in elderly subjects. Healthy 18 elders and 11 young students participated in this study. Subjects achieved the task which was to shift their center of gravity to maximal lateral position. We measured 2-dimensional position of acromion and ante-superior iliac spine (ASIS) in frontal plane. The maximal torques of dorsi / plantar flexion and medial / lateral rotation of ankle were standardized by % body weight (%BW) and used for evaluation of muscler forces of lower leg. According to the results of kinematic measurements of acromion and ASIS, we classified elders in Hip strategy (HS) group (n=13) and Ankle strategy (AS) group (n=5). We employed statistical analysis to compare these HS, AS, and young groups. Result of multi regression analysis of lateral shift of ASIS showed that the significant factors were inferior shift of Acromion for HS (R2=0.638, p<0.01, r=-0.799), and lateral shift of Acromion and plantar flexion torque for young group (R2=0.433, p<0.03, r=0.658). In conclusion, postural strategy with lateral transition of body weight in elders was namely Hip strategy which was controlled with moving mass of pelvic girdle as a counter mass of scapulary movement. However, a part of elderly subjects seemed to have same strategy to young subjects. Therefore studies with multiple view point including sensory system and brain functions will be needed for the future study.

The purpose of this study is to analyze the characteristics of deflection of center of foot pressure (CFP) that occurs during a side of center of gravity from the reference, attributed to trunk deflection and muscle force of lower limb. In addition, posture control in the elderly will also be reviewed. The study included 17 healthy elderly subjects and 14 students, adding up to a total of 31 subjects. The subject positioned himself on the force plate and performed an abnormal movement that resulted in a maximum shift of the center of gravity toward the right of the force plate. When the working CFP, acromion, and anterior superior iliac spine (ASIS) moved anteriorly, the deflection (Y-SD) was measured along with the muscle force of lower limb (% body weight). A correlation was sought between each of the above parameters. The results indicated a significant negative correlation between CFP Y-SD and muscle force required for trunk deflection in the elderly group (r=-0.51, p<0.05). In addition, a significant positive correlation was recognized between each of CFP Y-SD, acromion Y-SD, and ASIS Y-SD in the young group (r=0.75, 0.69, p<0.01). Based on the results of the elderly group, it was considered that the muscle force of the tibialis posterior muscle which contributes to the drop of metatarsus and forefoot, and anteroposterior homeostasis contributed to the control of the CFP deflection in the elderly. Thus, it is considered that the factors controlling CFP deflection that occurs during a lateral shift of the center of gravity in the elderly are different from those in the young. The results also suggest different mechanism for maintenance of posture in the two groups.

状況認識と判断を支援する警報装置は誤作動の可能性が完全に排除されていない。本研究では、複合タスク(棒制御タスクと2backタスク)の遂行中に警報音の誤作動(不警報、誤警報)を起こし、それによる情報認知作業のパフォーマンスへの影響を明らかにすることを目的とした。パフォーマンス指標として、棒制御タスクの反応時間、2backタスクの反応時間と正解率を分析した。不警報と比べ、誤警報の棒制御反応時間が有意に長かった。2backタスク反応時間には有意差が見られなかったが、不警報と比べて誤警報の正解率が有意に低く、警報誤作動開始の直後にもっとも正解率が低かった。手かかりとなるはずの警報の信頼性を疑わざるをえない状況下では、注意配分の容量やタイミングの乱れが生じ被験者の注意が散逸したことによって、反応が遅延したと考えられる。

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.

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.

重心側方移動時の高齢者の姿勢方略を2つのパターンに分類し,若年者の姿勢方略と比較,さらにその関連要因と思われる足圧中心移動範囲と下腿筋力との関係について分析した.高齢者を,高齢HS(Hip strategy)群,高齢AS(Ankle strategy)群に分類した.Acromion,ASISの各方向変位量の結果から,高齢AE・AS群の前額面上の姿勢方略の特徴が明らかとなった.動的姿勢制御の指標である足圧中心移動範囲の結果では,若年群に比して高齢E・AS群では,有意に移動範囲が狭くなった.若年群では足圧中心移動範囲の有意な説明変数は検出されなかったことから,今回の測定項目以外の要因が関連している可能性が示唆された

【目的】動的平衡機能に関連する指標の1つとして，足圧中心（Center of Foot Pressure：CFP）移動範囲の広さが挙げられるが，移動範囲の広さと同様にCFP随意移動時における動揺の特性やその規定因子について検討していくことも重要であると考える。本研究の目的は，CFP側方移動時におけるCFP及び体幹の前後方向動揺とその規定因子として考えられる下腿・足底筋活動との関係を分析し，高齢者の姿勢制御の一側面について検討を加えることである。<BR>【方法】対象は平衡機能に問題のない健常高齢者18名（平均年齢67.6±3.0歳），健常学生14名（平均年齢21.1±2.9歳）の計32名とした。全ての対象者には実験の趣旨を説明し同意を得た後，計測を行った。被験者にはForce Plate（G-5500；anima社）上で両上肢を組んだ開眼閉足位にて安静立位保持後，任意の速さでCFPを最大限右方向へ移動する運動課題を与え，運動遂行中の体幹とCFPの動揺量を変位の標準偏差で定義した。CFP側方向最大移動距離（X-MAX）とCFP前後方向動揺量（CFP Y-SD）をForce Plateで計測し，肩峰・上前腸骨棘の前後方向動揺量（肩峰 Y-SD，ASIS Y-SD）を磁気トラッキングセンサ（FASTRACK；polhemus社）を用いて計測した。さらに運動遂行中の右側下腿筋（前脛骨筋・ヒラメ筋・長腓骨筋）と母趾外転筋の活動電位を記録し最大随意収縮時の相対値（%MVC）を求めた。これらの各データを取り込み時に同期させ記録した。得られたデータからCFP のX-MAX・Y-SD，肩峰・ASIS Y-SD，下腿・母趾外転筋活動それぞれの相関関係をPearsonの積率相関係数を用いて分析した。<BR>【結果】高齢群でX-MAXと母趾外転筋の間に有意な正の相関を認めた（r=0.597, p<0.01）。若年群ではX-MAXと前脛骨筋の間に有意な正の相関を，肩峰・ASIS Y-SD・CFP Y-SDと母趾外転筋の間に有意な負の相関を認めた（r=-0.657, p<0.02）。<BR>【考察】X-MAXと筋活動との相関分析の結果から，高齢群では母趾外転筋の活動が，若年群では前脛骨筋の活動がCFP側方移動距離獲得要因の一つであることが考えられた。側方移動に関する我々の先行研究において高齢者は肩甲帯と骨盤が逆相動作することが確認されていることから，骨盤の逆(左)方向移動に伴う右足部の回内運動と母趾外転筋の床把握による制動作用により足部の固定性を高め， CFP移動距離を得ていたことが考えられた。また，若年群において体幹・CFP Y-SDと母趾外転筋の間に負の相関関係を認めたことから，若年者の体幹・CFPの前後動揺成分の制御には母趾外転筋の活動が関与していることが考えられた。さらに高齢群において，CFP・体幹の前後動揺と下腿・足底筋活動に有意な相関関係を認めなかったことから，高齢者の前後動揺成分の制御には，より中枢部の筋活動が関与している可能性が示唆された。

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.

The purpose of this study was to investigate the effect of the exposure to bright light on EEG activity and subjective sleepiness at rest and at the mental task during nocturnal sleep deprivation. Eight male subjects lay awake in semi-supine in a reclining seat from 21:00 to 04:30 under the bright (BL &gt 25001ux) or the dim (DL &lt 1501ux) light conditions. During the sleep deprivation, the mental task (Stroop color-word conflict test: CWT) was performed each 15min in one hour. EEG, subjective sleepiness, rectal and mean skin temperatures and urinary melatonin concentrations were measured. The subjective sleepiness increased with time of sleep deprivation during both rest and CWT under the DL condition. The exposure to bright light delayed for 2 hours the increase in subjective sleepiness at rest and suppressed the increase in that during CWT. The bright light exposure also delayed the increase in the theta and alpha wave activities in EEG at rest. In contrast, the effect of the bright light exposure on the theta and alpha wave activities disappeared by CWT. Additionally, under the BL condition, the entire theta activity during CWT throughout nocturnal sleep deprivation increased significantly from that in a rest condition. Our results suggest that the exposure to bright light throughout nocturnal sleep deprivation influences the subjective sleepiness during the mental task and the EEG activity, as well as the subjective sleepiness at rest. However, the effect of the bright light exposure on the EEG activity at the mental task diminishes throughout nocturnal sleep deprivation.

The purpose of the present paper is to describe and evaluate the polynomial models for predicting the muscular work capacity of the upper limb during sustained holding tasks. This research was concerned with the relationship between indicators of performance, i.e., specific posture or specific level of maximum voluntary contraction (MVC), and then modeling the functional data based on experimental results to estimate factors that may have an effect on task performance. To this end, we designed an experiment using 10 subjects in which each subject performed sustained isometric shoulder and elbow flexion endurance exercise under 27 conditions [3 shoulder angles (SA)X3 elbow angles (EA)X3 levels of %MVC]. Throughout all experiments, subjective perception of effort was assessed using the Borg scale, every 60, 30, and 10 s during the 20%, 40%, and 60% MVC tests, respectively. Proposal models were represented by three approaches: model A: estimation of endurance time (ET), with input variables such as SA, EA, and %MVC model B: estimation of recommendation time (RT, the time during which the operator was able to maintain a position under the desired condition), with input variables such as SA, EA, %MVC, and required rate on the Borg scale and model C: estimation of limit strength or %MVC, with input variables such as SA, EA, request limit time for work (LT), and required rate on the Borg scale. Statistical analysis indicated that the three proposal estimation models based on polynomial regression functions showed high significance (p&lt 0.0001). The proposal models suggested and recommended the possibility of finding the best positions entailing the reduction and minimization of total muscular strain from manual material handling tasks in different work situations, with the consequent increase in work efficiency.