岩永 光一

The effect of active recovery at a decreasing % of MVC following intense muscular exercise on intramuscular pH was investigated in vivo using P-31-MRS. Seven healthy men participated, and their right wrist flexor muscle group was examined. The subjects were asked to flex their right wrist at 60 % of the maximum voluntary contraction (MVC) every 2s until the intracellular pH in the wrist flexor muscle decreased to 6.4. After the exercise period, the subjects underwent active or passive recovery for 10 min. For the active recovery (AR), the subject was asked to continue exercising at a decreasing % of MVC, decreasing from 25 to 5% MVC every two min during AR. P-31-MR-spectra were obtained throughout the experiments, and from the spectra the intracellular pH (pHi) was calculated as an indicator of intracellular events. AR data were compared to data collected during passive recovery (PR). During AR, the pHi increased immediately after the exercise period; whereas in that of PR, it did not recover within 5 minutes after exercise. The results suggested that mild exercise was an effective manoeuver to promote recovery from intramuscular metabolic acidosis.

[はじめに] ヒトの立位姿勢の安定性を考えていくとき，支持基底面内での重心を足部に投影した点，すなわち足圧中心（以下，CFP）の随意的移動範囲が重要であると考えられる。運動方略における自己始動動揺制御に用いられる運動に関する先行研究では，主に前後方向を中心に述べられているものが多い。今回，いくつかの制限下における自己始動動揺の制御運動に関して，側方移動時の高齢者と若年者の特性を調べ検討したので報告する。<BR>[対象] 平衡機能に問題のない健常高齢者19名（平均年齢67.9±3.7歳），健常学生15名（平均年齢20.9±2.5歳）の計34名とした。<BR>[実験方法] 対象（高齢）者には実験の趣旨を説明し同意を得た後，計測を行った。被験者にはフォースプレート（重心動揺計G-6100；アニマ社）上で両上肢を組んだ開眼ロンベルグ肢位をとり，以下のような課題動作を行わせた。安静立位保持後，転倒しない範囲でCFPを最大限右方向へ移動し，その位置で立位姿勢を5秒間保持，もとの肢位へ戻る。この際の側方CFP移動範囲を測定した。また，動作中の体幹の動きを知るために，両肩峰・両上前腸骨棘（以下，ASIS）に磁気トラッキング装置センサ（Fastrak；Polhemus社）を取り付け，各データを取り込み時に同期させ記録した。<BR>[分析方法] CFP移動範囲は両側足幅の百分率で算出し，体幹の動きは前額面上における右肩峰（側方，下方，斜方向成分），右ASIS（側方向成分）の動作開始位置から最大移動位置までの距離を求めた。得られたデータよりCFP移動範囲を高齢群・若年群で比較検討し，右肩峰・右ASISの各方向移動距離とCFP移動範囲の各データの相関関係を求めた。統計処理は高齢群と若年群との差の検定にはWelch testを用い，各データの相関にはPearsonの相関係数を用いた。<BR>[結果] 高齢群のCFP移動範囲，ASIS右方向移動距離は若年群に比較して有意に小さかった（p<0.001）。高齢群においてはCFP移動範囲と肩峰斜方向移動距離の相関係数は0.739であり高い相関を認めた（p<0.001）。若年群においてはCFP移動範囲とASIS側方向移動距離の相関係数が0.567（p<0.05）で相関を認めた。<BR>[考察] 高齢群においてCFP移動範囲と肩峰斜方向移動距離に高い正相関を認めたことは，高齢者では随意的にCFPを側方移動させる際には，主に体幹の側屈（傾き）を用いていることが考えられた。一方，若年群ではそれらに相関関係は認めず，CFP移動範囲とASISの側方向移動距離とに低いながらも正相関が認められたことから，若年者のCFP側方向移動は主に骨盤の水平移動を用いていることが考えられた。これらのことから，随意的な側方向CFP移動時においては，前後方向と同じように高齢者と若年者では異なった姿勢方略を用い，さらにいくつかのパターンがあることが考えられた。<BR>

To investigate the influence of nonthermal factors in the time-of-day effect on the sweating response to maintained static exercise, eight healthy male subjects performed handgrip exercise at 20%, 35% and 50% maximal voluntary contraction (MVC) for 60 s at 0600 hours (morning) and at 1800 hours (evening). Oesophageal temperature (T-oes) before the experiment showed a diurnal rhythm [mean (SEM)] [36.3 (0.1) (morning) compared to 36.8 (0.1) degreesC (evening), P &lt; 0.01]. Experiments were conducted with subjects in a state of mild hyperthermia during which the mean skin temperature (T-sk) was kept constant at 35.5-36.5 degreesC using a water-perfused. suit to activate sudomotor responses. The T-oes and mean T-sk remained stable during the pre-exercise, handgrip exercise and recovery periods. The response in sweating rate (DeltaSR) on the chest and forearm to handgrip exercise increased significantly with increasing exercise intensity in both the morning and evening tests (P &lt; 0.05). The DeltaSR on the palm did not change significantly with increasing exercise intensity in the morning test (P &gt; 0.1). During hand-rip exercise at 50% MVC only, DeltaSR on the chest, forearm and palm in the evening was significantly higher than in the morning (P &lt; 0.05). On the other hand, mean arterial blood pressure and the rating of perceived exertion during 50% WC handgrip exercise were not significantly different between the morning and evening (P &gt; 0.1). These results indicate the presence of a time-of-day effect on nonthermal control of the sweating response to isometric handgrip exercise, and that this effect is dependent on exercise intensity.

To investigate the behavior of mechanomyogram (MMG) and electromyogram (EMG) signals in the time and frequency domains during sustained isometric contraction, MMG and surface EMG were obtained simultaneously from four muscles: upper trapezius (TP), anterior deltoid (DL), biceps brachii (BB), and brachioradialis (BR) of 10 healthy male subjects. Experimental conditions consisted of 27 combinations of 9 postures [3 shoulder angles (SA): 0°, 30°, 60° and 3 elbow angles (EA): 120°, 90°, 60°] and 3 contraction levels: 20%, 40%, and 60% of maximum voluntary contraction (MVC). Subjective evaluations of fatigue were also assessed using the Borg scale at intervals of 60, 30, and 10 sec at 20%, 40%, and 60% MVC tests, respectively. The mean power frequency (MPF) and root mean square (RMS) of both signals were calculated. The current study found clear and significant relationships among physiological and psychological parameters on the one hand and SA and EA on the other. EA's effect on MVC was found to be significant. SA had a highly significant effect on both endurance time and Borg scale. In all experimental conditions, significant correlations were found between the changes in MPF and RMS of EMG in BB with SA and EA (or muscle length). In all four muscles, MMG frequency content was two or three times lower than EMG frequency content. During sustained isometric contraction, the EMG signal showed the well-known shift to lower frequencies (a continuous decrease from onset to completion of the contraction). In contrast, the MMG spectra did not show any shift, although its form changed (generally remaining about constant). Throughout the contraction, increased RMS of EMG was found for all tests, whereas in the MMG signal, a significant progressive increase in RMS was observed only at 20% MVC in all four muscles. This supports the hypothesis that the RMS amplitude of the MMG signal produced during contraction is highly correlated with force production. Possible explanations for this behavioral difference between the MMG and EMG signals are discussed.

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°, 90°, and 60°) 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° was found to be significantly lower than 90° and 60°, 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 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.

Background. To investigate the effects of specific warm-up at various intensities on energy metabolism during subsequent intense exercise. Methods. Experimental design: specific warm-up was consisted of 3 sets of wrist flexions for 5 min, with each set followed by a 3-min rest. The intensity of specific warm-up was set at 20%, 30% or 40% of maximal voluntary contraction (MVC). The subjects then performed a set of wrist flexions at 60% MVC for 4 min as the criterion exercise, For the control experiment, criterion exercise was done without specific warm-up. Participants: Five healthy volunteers. Measurements: using phosphorus-31 magnetic resonance spectroscopy, spectra were obtained from the wrist flexor muscles to determine the ratio of inorganic phosphate to phosphocreatine (Pi/PCr) and intracellular pH. Results. The Pi/PCr during the criterion exercise after specific warm-up at any intensity was not significantly different from that without specific warm-up. The intracellular pH during the criterion exercise after specific warm-up at 30% or 40% MVC was significantly higher than that without specific warm-up. Conclusions. These results indicate that mild warm-up exercise could inhibit the development of intracellular acidosis during subsequent intense exercise.

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.

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.

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&lt 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.

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 timewindow RMS-to-DC converter. The prototype was battery-driven and well-shielded to minimize external noise interference.

Seven male students were exposed to four varied air temperature environments: hot (37℃) to neutral (27℃) (HN), neutral to hot (NH), cool (17℃) 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 (Δ(T_<sk> - T_a)) was not so different among the four experimental conditions, and the correlation between thermal sensation and heat flux or Δ(T_<sk> - T_a) was fairly good. The multiple regression equation of the thermal sensation (TS) on 15 sites of skin temperature (T_<sk>; ℃) was calculated and the coefficient of determination (R) 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 Δ(T_<sk> - T_a) (℃) at 4 sites. They were as follows: TS=2.04 - 0.016 H_<right> - 0.036 H_<left>; R=0.717, TS=1.649 + 0.013 Δ(T_<sk> - T_a)_<UpperArm> - 0.036 Δ(T_<sk> - T_a)_<Chest> - 0.223 Δ(T_<sk> - T_a)_<Thigh> - 0.836 Δ(T_<sk> - T_a)_<LowerLeg>; R=0.752, respectively.