Rissanen S, Oksa J, Rintamäki H, Tokura H
Oulu Regional Institute of Occupational Health, Laboratory of Physiology, Oulu, Finland.
Eur J Appl Physiol Occup Physiol. 1996;73(1-2):163-8. doi: 10.1007/BF00262826.
Thermal responses and muscle performance in humans were studied during rest and exercise in a cool environment with different clothing distributions over the legs. Nine female subjects were exposed to 5 degrees C wearing shorts (SS), trousers with long legs (LL) or trousers with one long leg and one short leg (LS: LSc covered leg, LSu uncovered leg). The subjects also wore T-shirts and long-sleeved shirts. The subjects were seated for 60 min and after this they performed light stepping exercise for a further 60 min. Rectal temperature (T(re)) and skin temperature from seven (LL, SS) or nine sites (LS) were measured continuously. Surface electromyography (EMG) from three muscles (biceps femoris, gastrocnemius and tibialis anterior) were recorded during the exercise from six subjects. Integrated EMG (iEMG) and mean power frequency (MPF) were used to describe muscle activity. The T(re) was virtually unchanged during rest in every ensemble, whereas during exercise T(re) was significantly lower in SS than in LL. Mean skin temperature (T(sk)) decreased during rest in every ensemble, being significantly lower in SS than in LL. After the rest period local T(sk) of thigh and calf were significantly lower in SS than in LL and they were also lower in LSu than in LSc. At the beginning of the exercise the iEMG of the tibialis anterior muscle in SS and LL averaged 84 (SEM 7) and 64 (SEM 3) mu V (P <0.05), respectively. Respective values for LSu and LSc were 86 (SEM 9) and 66 (SEM 6) mu V (P <0.05). The MPF of the tibialis anterior muscle was significantly higher in LL 102 (SEM 5) Hz than in SS 90 (SEM 5) Hz (P <0.05) and similarly the MPF of the gastrocnemius muscle was also higher in LL 111 (SEM 5) Hz than in SS 100 (SEM 5) Hz (P < 0.05). It was concluded that exposing bare legs to a cool environment enhanced the motor unit activity in relation to covered legs. This would suggest that wearing shorts in a cool environment may, at the beginning of exercise, result in higher (about 25 percent) EMG activity and this may reflect increased muscle strain in comparison with wearing long trousers. Our results showing a unilateral increase in EMG activity during unilateral cooling suggest that the increase of strain is restricted to the uncovered part of the limb.
在凉爽环境中休息和运动期间，研究了不同腿部着装分布情况下人体的热反应和肌肉表现。九名女性受试者分别穿着短裤（SS）、长裤（LL）或一条长裤一条短裤（LS：LSc为覆盖腿，LSu为未覆盖腿）暴露在5摄氏度环境中。受试者还穿着T恤和长袖衬衫。受试者先静坐60分钟，之后再进行60分钟的轻度踏步运动。连续测量直肠温度（T(re)）以及来自七个部位（LL、SS）或九个部位（LS）的皮肤温度。在运动过程中，对六名受试者的三块肌肉（股二头肌、腓肠肌和胫骨前肌）进行表面肌电图（EMG）记录。采用积分肌电图（iEMG）和平均功率频率（MPF）来描述肌肉活动。在每种着装组合的休息期间，T(re)基本保持不变，而在运动期间，SS组的T(re)显著低于LL组。在每种着装组合的休息期间，平均皮肤温度（T(sk)）均下降，SS组显著低于LL组。休息期过后，SS组大腿和小腿的局部T(sk)显著低于LL组，且LSu组低于LSc组。运动开始时，SS组和LL组胫骨前肌的iEMG平均分别为84（标准误7）和64（标准误3）微伏（P<0.05）。LSu组和LSc组的相应值分别为86（标准误9）和66（标准误6）微伏（P<0.05）。LL组胫骨前肌的MPF显著高于SS组，分别为102（标准误5）赫兹和90（标准误5）赫兹（P<0.05），同样，LL组腓肠肌的MPF也高于SS组，分别为111（标准误5）赫兹和100（标准误5）赫兹（P<0.05）。研究得出结论，将裸露的腿部暴露在凉爽环境中会增强与覆盖腿部相比的运动单位活动。这表明在凉爽环境中穿短裤在运动开始时可能会导致更高（约25%）的肌电图活动，这可能反映出与穿长裤相比肌肉应变增加。我们的结果显示单侧冷却期间肌电图活动单侧增加，这表明应变增加仅限于肢体未覆盖部分。
