The influence of circulatory difference on muscle oxygenation and fatigue during intermittent static dorsiflexion |
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Authors: | Masanobu Tachi Motoki Kouzaki Hiroaki Kanehisa Tetsuo Fukunaga |
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Affiliation: | (1) Laboratory of Sports Sciences, Department of Life Sciences, The University of Tokyo, 3–8–1 Komaba, Meguro, Tokyo, Japan 153–8902;(2) Department of Sports Sciences, School of Human Sciences, Waseda University, 2–579–15 Mikajima, Tokorozawa, Saitama, Japan 359–1192 |
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Abstract: | This study aimed to examine the influences of circulatory difference on the utilization of O2 and the progression of fatigue in the tibialis anterior (TA) muscle during dorsiflexion exercise, with reference to different body postures. The subjects performed intermittent static dorsiflexion at 50% of maximal voluntary contraction (MVC) up to exhaustion with the right leg either up or down relative to the heart. These exercises were performed with and without occluding muscle blood flow. Simultaneously with the surface electromyogram (EMG) measurement, total hemoglobin volume change and tissue oxygenation (S tO2) of TA were measured using near-infrared spectroscopy (NIRS). When the subjects performed an exhaustive intermittent dorsiflexion exercise at 50% MVC, the endurance time decreased in the leg up position. Also, the progression of fatigue in TA detected using EMG signals (i.e. integrated EMG and mean power frequency of EMG) was faster with the leg elevated. The NIRS data indicated a lower blood volume and S tO2 with the leg up than with the leg down during the exercise, which suggests that the deficit in the O2 supply to exercising muscles demand was more apparent in the leg up position. However, these differences in EMG and NIRS data disappeared when the blood flow was restricted in both positions. From these results it is concluded that the difference in exercising muscle oxygenation between two different body postures influenced the progression of muscle fatigue and caused the difference in endurance performance. |
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Keywords: | Muscle fatigue Electromyogram Near-infrared spectroscopy Body posture |
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