Neuromuscular drive and force production are not altered during bilateral contractions
Kinesiology and Health Science, Faculty of Pure and Applied Science, York University, Toronto, Ontario, Canada M3J 1P3 Jakobi, J. M., and E. Cafarelli. Neuromuscular drive and force production are not altered during bilateral contractions. J. Appl. Physiol. 84(1): 200-206, 1998. Several investigator...
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Veröffentlicht in: | Journal of applied physiology (1985) 1998-01, Vol.84 (1), p.200-206 |
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Zusammenfassung: | Kinesiology and Health Science, Faculty of Pure and Applied
Science, York University, Toronto, Ontario, Canada M3J 1P3
Jakobi, J. M., and E. Cafarelli. Neuromuscular drive
and force production are not altered during bilateral contractions. J. Appl. Physiol. 84(1): 200-206, 1998. Several investigators have studied the deficit in maximal
voluntary force that is said to occur when bilateral muscle groups
contract simultaneously. A true bilateral deficit (BLD) would suggest a
significant limitation of neuromuscular control; however, some of the
data from studies in the literature are equivocal. Our purpose was to
determine whether there is a BLD in the knee extensors of untrained
young male subjects during isometric contractions and whether this
deficit is associated with a decreased activation of the quadriceps,
increased activation of the antagonist muscle, or an alteration in
motor unit firing rates. Twenty subjects performed unilateral (UL) and bilateral (BL) isometric knee extensions at 25, 50, 75, and 100% maximal voluntary contraction. Total UL and BL force ( 3%) and maximal rate of force generation ( 2.5%) were not significantly different. Total UL and BL maximal vastus lateralis electromyographic activity (EMG; 2.7 ± 0.28 vs. 2.6 ± 0.24 mV) and
coactivation (0.17 ± 0.02 vs. 0.20 ± 0.02 mV) were also not
different. Similarly, the ratio of force to EMG during submaximal UL
and BL contractions was not different. Analysis of force production by
each leg in UL and BL conditions showed no differences in force, rate
of force generation, EMG, motor unit firing rates, and coactivation.
Finally, assessment of quadriceps activity with the twitch
interpolation technique indicated no differences in the degree of
voluntary muscle activation (UL: 93.6 ± 2.51 Hz, BL: 90.1 ± 2.43 Hz). These results provide no evidence of a significant limitation
in neuromuscular control between BL and UL isometric contractions of
the knee extensor muscles in young male subjects.
twitch interpolation; coactivation; average motor unit firing rate; bilateral deficit; maximal voluntary contraction
The Journal of Applied Physiology 84(1):200-206
0161-7567/98 $5.00
Copyright © 1998 the American Physiological Society |
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ISSN: | 8750-7587 1522-1601 |
DOI: | 10.1152/jappl.1998.84.1.200 |