| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
1 Department of Kinesiology and Applied Physiology, University of Colorado, Boulder, Colorado 80309-0354; and 2 Institut National de la Santé et de la Recherche Médicale/Equipe de Recherche et d'Innovation Technologique 0207, Unité de Formation et de Recherche Sciences et Techniques des Activités Physiques et Sportive, Université de Bourgogne, 21078 Dijon, France
Twenty-four men (n = 11) and women (n = 13) supported an inertial load equivalent to 20% of the maximum voluntary contraction force with the elbow flexor muscles for as long as possible while maintaining a constant elbow angle at 90°. Endurance time did not differ on the three occasions that the task was performed (320 ± 149 s; P > 0.05), and there was no difference between women (360 ± 168 s) and men (273 ± 108 s; P = 0.11). The rate of increase in average electromyogram (EMG) for the elbow flexor muscles was similar across sessions (P > 0.05). However, average EMG during the fatiguing task increased for the long head of biceps brachii, brachioradialis, and brachialis (P < 0.05) but not for the short head of biceps brachii. Furthermore, the average EMG for the brachialis was greater at the start and end of the contraction compared with the other elbow flexor muscles. The rate of bursts in EMG activity increased during the fatiguing contraction and was greater in brachialis (1.0 ± 0.2 bursts/min) compared with the other elbow flexor muscles (0.5 ± 0.1 bursts/min). The changes in the standard deviation of acceleration, mean arterial pressure, and heart rate during the fatiguing contractions were similar across sessions. These findings indicate that the EMG activity, which reflects the net excitatory and inhibitory input received by the motoneurons in the spinal cord, was not adaptable over repeat sessions for the maintain-position task. Furthermore, these results contrast those from a previous study (Hunter SK and Enoka RM. J Appl Physiol 94: 108-118, 2003) when the goal of the isometric contraction was to maintain a constant force. These results, from a series of studies on the elbow flexor muscles, indicate that the type of load supported during the fatiguing contraction influences the extent to which endurance time can change with repeat performances of the task.
fatigue; electromyography; task; sex; fluctuations in acceleration
This article has been cited by other articles:
|
|
 |
|
  S. K. Hunter, T. Yoon, J. Farinella, E. E. Griffith, and A. V. Ng Time to task failure and muscle activation vary with load type for a submaximal fatiguing contraction with the lower leg J Appl Physiol, August 1, 2008; 105(2): 463 - 472. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. Rudroff, D. Staudenmann, and R. M. Enoka Electromyographic measures of muscle activation and changes in muscle architecture of human elbow flexors during fatiguing contractions J Appl Physiol, June 1, 2008; 104(6): 1720 - 1726. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Klass, M. Levenez, R. M. Enoka, and J. Duchateau Spinal Mechanisms Contribute to Differences in the Time to Failure of Submaximal Fatiguing Contractions Performed With Different Loads J Neurophysiol, March 1, 2008; 99(3): 1096 - 1104. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Levenez, S. J. Garland, M. Klass, and J. Duchateau Cortical and Spinal Modulation of Antagonist Coactivation During a Submaximal Fatiguing Contraction in Humans J Neurophysiol, February 1, 2008; 99(2): 554 - 563. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. Rudroff, B. K. Barry, A. L. Stone, C. J. Barry, and R. M. Enoka Accessory muscle activity contributes to the variation in time to task failure for different arm postures and loads J Appl Physiol, March 1, 2007; 102(3): 1000 - 1006. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. J. Mottram, K. S. Maluf, J. L. Stephenson, M. K. Anderson, and R. M. Enoka Prolonged Vibration of the Biceps Brachii Tendon Reduces Time to Failure When Maintaining Arm Position With a Submaximal Load J Neurophysiol, February 1, 2006; 95(2): 1185 - 1193. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. J. Mottram, E. A. Christou, F. G. Meyer, and R. M. Enoka Frequency Modulation of Motor Unit Discharge Has Task-Dependent Effects on Fluctuations in Motor Output J Neurophysiol, October 1, 2005; 94(4): 2878 - 2887. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Levenez, C. Kotzamanidis, A. Carpentier, and J. Duchateau Spinal reflexes and coactivation of ankle muscles during a submaximal fatiguing contraction J Appl Physiol, September 1, 2005; 99(3): 1182 - 1188. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. S. Maluf and R. M. Enoka Task failure during fatiguing contractions performed by humans J Appl Physiol, August 1, 2005; 99(2): 389 - 396. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. J. Mottram, J. M. Jakobi, J. G. Semmler, and R. M. Enoka Motor-Unit Activity Differs With Load Type During a Fatiguing Contraction J Neurophysiol, March 1, 2005; 93(3): 1381 - 1392. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
N. Place, N. A. Maffiuletti, Y. Ballay, and R. Lepers Twitch potentiation is greater after a fatiguing submaximal isometric contraction performed at short vs. long quadriceps muscle length J Appl Physiol, February 1, 2005; 98(2): 429 - 436. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. K. Hunter, A. Critchlow, and R. M. Enoka Influence of aging on sex differences in muscle fatigability J Appl Physiol, November 1, 2004; 97(5): 1723 - 1732. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. K. Hunter, A. Critchlow, I.-S. Shin, and R. M. Enoka Men are more fatigable than strength-matched women when performing intermittent submaximal contractions J Appl Physiol, June 1, 2004; 96(6): 2125 - 2132. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Klass, N. Guissard, and J. Duchateau Limiting mechanisms of force production after repetitive dynamic contractions in human triceps surae J Appl Physiol, April 1, 2004; 96(4): 1516 - 1521. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
L Rochette, S. K. Hunter, N Place, and R Lepers Activation varies among the knee extensor muscles during a submaximal fatiguing contraction in the seated and supine postures J Appl Physiol, October 1, 2003; 95(4): 1515 - 1522. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Visit Other APS Journals Online |
