Electromyographic activity in lower limb muscles is temporally associated with the slow phase of oxygen uptake during cycling

Green, Simon, Smith, Nigel J., & Kerr, Graham K. (2010) Electromyographic activity in lower limb muscles is temporally associated with the slow phase of oxygen uptake during cycling. Scandinavian Journal of Medicine & Science in Sports, 20(2), pp. 310-319.

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Although the "slow" phase of pulmonary oxygen uptake (Vo2) appears to represent energetic processes in contracting muscle, electromyographic evidence tends not to support this. The present study assessed normalized integrated electromyographic (NIEMG) activity in eight muscles that act about the hip, knee and ankle during 8 min of moderate (<ventilatory threshold) and very heavy (>ventilatory threshold) cycling in six male cyclists. (Vo2) was measured breath by breath during four repeated trials at each of the two intensities. Moderate and very heavy exercise followed a 4-min period of light exercise (50 W). During moderate exercise the slow (Vo2) phase was absent and NIEMG in all muscles did not increase after the first minute of exercise. During very heavy exercise, the slow phase emerged (time delay=58 ± 16 s) and increased progressively (time constant=120 ± 35 s) to an amplitude (0.83 ± 0.16 L/min) that was approximately 21% of the total (Vo2) response. This slow (Vo2) phase coincided with a significant increase in NIEMG in most muscles, and differences in NIEMG activities between the two intensities revealed "slow" muscle activation profiles that differed between muscles in terms of the onset, amplitude and shape of these profiles. This supports the hypothesis that the slow (Vo2) phase is a function of these different slow muscle activation profiles.

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ID Code: 32051
Item Type: Journal Article
Refereed: Yes
Keywords: Cycling, Oxygen Uptake, Fast Phase, Slow Phase, Motor Unit, Fatigue
DOI: 10.1111/j.1600-0838.2009.00893.x
ISSN: 0905-7188
Subjects: Australian and New Zealand Standard Research Classification > MEDICAL AND HEALTH SCIENCES (110000) > HUMAN MOVEMENT AND SPORTS SCIENCE (110600)
Divisions: Current > QUT Faculties and Divisions > Faculty of Health
Current > Institutes > Institute of Health and Biomedical Innovation
Current > Schools > School of Exercise & Nutrition Sciences
Deposited On: 06 May 2010 03:23
Last Modified: 29 Feb 2012 14:06

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