Relationship between muscle fatigue and oxygen uptake during cycle ergometer exercise with different ramp slope increments |
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Authors: | Tetsuo Takaishi Takashi Ono Yoshifumi Yasuda |
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Institution: | (1) College of General Education, Nagoya City University, 467 Mizuho-cho, Mizuho-ku, Nagoya, Japan;(2) Graduate School, Aichi University of Education, 448 Ikegaya-cho, Kariya, Japan;(3) Toyohashi University of Technology, 440 Hibarigaoka, Tenpaku-cho, Toyohashi, Japan |
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Abstract: | Summary The surface electromyogram (EMG) from active muscle and oxygen uptake (
) were studied simultaneously to examine changes of motor unit (MU) activity during exercise tests with different ramp increments. Six male subjects performed four exhausting cycle exercises with different ramp slopes of 10, 20, 30 and 40 W · min–1 on different days. The EMG signals taken from the vastus lateralis muscle were stored on a digital data recorder and converted to obtain the integrated EMG (iEMG). The
was measured, with 20-s intervals, by the mixing chamber method. A non-linear increase in iEMG against work load was observed for each exercise in all subjects. The break point of the linear relationship of iEMG was determined by the crossing point of the two regression lines (iEMGbp). Significant differences were obtained in the exercise intensities corresponding to maximal oxygen uptake (
) and the iEMGbp between 10 and 30, and 10 and 40 W · min –1 ramp exercises (P < 0.05). However, no significant differences were obtained in
and
corresponding to the iEMGbp during the four ramp exercises. With respect to the relationship between
and exercise intensity during the ramp increments, the
-exercise intensity slope showed significant differences only for the upper half (i.e. above iEMGbp). These results demonstrated that the
and
at which a nonlinear increase in iEMG was observed were not varied by the change of ramp slopes but by the exercise intensity corresponding to
and the iEMGbp was varied by the change of ramp slopes. In addition, the significant differences in the
exercise intensity slopes for the upper half of the tests would suggest that the recruitment patterns of MU and/or muscle metabolic state might be considerably altered depending upon the ramp slope increments. |
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Keywords: | Muscle fatigue Integrated electromyogram Maximum oxygen uptake Electromyogram break point Oxygen uptake response |
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