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JOURNAL
OF
SPORTS SCIENCE &
MEDICINE
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Research
article
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SELECTIVE ACTIVATION OF THE RECTUS ABDOMINIS MUSCLE DURING LOW-INTENSITY AND FATIGUING TASKS |
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Paulo H. Marchetti1  ,
André F. Kohn2 and Marcos Duarte1 |
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1School of Physical Education and Sport, University of São Paulo, Brazil, 2Escola Politécnica, PTC, University of São Paulo, Brazil |
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© Journal of Sports Science and Medicine (2011) 10, 322 - 327 |
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| ABSTRACT | |||
| In order to understand the potential selective activation of the
rectus abdominis muscle, we conducted two experiments. In the first, subjects
performed two controlled isometric exercises: the curl up (supine trunk
raise) and the leg raise (supine bent leg raise) at low intensity (in which
only a few motor units are recruited). In the second experiment, subjects
performed the same exercises, but they were required to maintain a certain
force level in order to induce fatigue. We recorded the electromyographic
(EMG) activities of the lower and upper portions of the rectus abdominis
muscle during the exercises and used spatial-temporal and frequency analyses
to describe muscle activation patterns. At low-intensity contractions, the
ratio between the EMG intensities of the upper and lower portions during
the curl up exercise was significantly larger than during the leg raise
exercise (p = 0.02). A cross-correlation analysis indicated that the signals
of the abdominal portions were related to each other and this relation did
not differ between the tasks (p = 0.12). In the fatiguing condition, fatigue
for the upper portion was higher than for the lower portion during the curl
up exercise (p = 0.008). We conclude that different exercises evoked, to
a certain degree, individualized activation of each part of the rectus abdominis
muscle, but different portions of the rectus abdominis muscle contributed
to the same task, acting like a functional unit. These results corroborate
the relevance of varying exercise to modify activation patterns of the rectus
abdominis muscle. Key words: Motor control, electromyography, biomechanics, exercise. |
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