HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Carpentier, A. Articles by Hainaut, K. Search for Related Content PubMed PubMed Citation Articles by Carpentier, A. Articles by Hainaut, K.

Motor unit behaviour and contractile changes during fatigue in the human first dorsal interosseus

Alain Carpentier, Jacques Duchateau and Karl Hainaut

1. In 67 single motor units, the mechanical properties, the recruitment and derecruitment thresholds, and the discharge rates were recorded concurrently in the first dorsal interosseus (FDI) of human subjects during intermittent fatiguing contractions. The task consisted of isometric ramp-and-hold contractions performed at 50 % of the maximal voluntary contraction (MVC). The purpose of this study was to examine the influence of fatigue on the behaviour of motor units with a wide range of activation thresholds.
2. For low-threshold (< 25 % MVC) motor units, the mean twitch force increased with fatigue and the recruitment threshold either did not change or increased. In contrast, the twitch force and the activation threshold decreased for the high-threshold (> 25 % MVC) units. The observation that in low-threshold motor units a quick stretch of the muscle at the end of the test reset the unit force and recruitment threshold to the prefatigue value suggests a significant role for fatigue-related changes in muscle stiffness but not twitch potentiation or motor unit synchronization.
3. Although the central drive intensified during the fatigue test, as indicated by an increase in surface electromyogram (EMG), the discharge rate of the motor units during the hold phase of each contraction decreased progressively over the course of the task for motor units that were recruited at the beginning of the test, especially the low-threshold units. In contrast, the discharge rates of newly activated units first increased and then decreased.
4. Such divergent behaviour of low- and high-threshold motor units could not be individually controlled by the central drive to the motoneurone pool. Rather, the different behaviours must be the consequence of variable contributions from motoneurone adaptation and afferent feedback from the muscle during the fatiguing contraction.

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]

				Z. A. Riley, A. H. Maerz, J. C. Litsey, and R. M. Enoka Motor unit recruitment in human biceps brachii during sustained voluntary contractions J. Physiol., April 15, 2008; 586(8): 2183 - 2193. [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]

				J. L. Taylor and S. C. Gandevia A comparison of central aspects of fatigue in submaximal and maximal voluntary contractions J Appl Physiol, February 1, 2008; 104(2): 542 - 550. [Abstract] [Full Text] [PDF]

				S. Vucic, A. V Krishnan, and M. C Kiernan Fatigue and activity dependent changes in axonal excitability in amyotrophic lateral sclerosis J. Neurol. Neurosurg. Psychiatry, November 1, 2007; 78(11): 1202 - 1208. [Abstract] [Full Text] [PDF]

				B. K. Barry and R. M. Enoka The neurobiology of muscle fatigue: 15 years later Integr. Comp. Biol., October 1, 2007; 47(4): 465 - 473. [Abstract] [Full Text] [PDF]

				D. Falla, D. Farina, M. K. Dahl, and T. Graven-Nielsen Muscle pain induces task-dependent changes in cervical agonist/antagonist activity J Appl Physiol, February 1, 2007; 102(2): 601 - 609. [Abstract] [Full Text] [PDF]

				M. Burnley, J. H. Doust, and A. M. Jones Time required for the restoration of normal heavy exercise VO2 kinetics following prior heavy exercise J Appl Physiol, November 1, 2006; 101(5): 1320 - 1327. [Abstract] [Full Text] [PDF]

				J. J. Kavanagh, S. Morrison, and R. S. Barrett Lumbar and cervical erector spinae fatigue elicit compensatory postural responses to assist in maintaining head stability during walking J Appl Physiol, October 1, 2006; 101(4): 1118 - 1126. [Abstract] [Full Text] [PDF]

				S. K. Hunter, J. M. Schletty, K. M. Schlachter, E. E. Griffith, A. J. Polichnowski, and A. V. Ng Active hyperemia and vascular conductance differ between men and women for an isometric fatiguing contraction J Appl Physiol, July 1, 2006; 101(1): 140 - 150. [Abstract] [Full Text] [PDF]

				C. S. Klein, C. K. Hager-Ross, and C. K. Thomas Fatigue properties of human thenar motor units paralysed by chronic spinal cord injury J. Physiol., May 15, 2006; 573(1): 161 - 171. [Abstract] [Full Text] [PDF]

				A. J. Fuglevand, A. P. Dutoit, R. K. Johns, and D. A. Keen Evaluation of plateau-potential-mediated 'warm up' in human motor units J. Physiol., March 15, 2006; 571(3): 683 - 693. [Abstract] [Full Text] [PDF]

				C. K. Thomas, R. S. Johansson, and B. Bigland-Ritchie EMG Changes in Human Thenar Motor Units With Force Potentiation and Fatigue J Neurophysiol, March 1, 2006; 95(3): 1518 - 1526. [Abstract] [Full Text] [PDF]

				S. K. Hunter, A. Critchlow, and R. M. Enoka Muscle endurance is greater for old men compared with strength-matched young men J Appl Physiol, September 1, 2005; 99(3): 890 - 897. [Abstract] [Full Text] [PDF]

				B.M. Meyers and E. Cafarelli Caffeine increases time to fatigue by maintaining force and not by altering firing rates during submaximal isometric contractions J Appl Physiol, September 1, 2005; 99(3): 1056 - 1063. [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]

				A. Adam and C. J. De Luca Firing rates of motor units in human vastus lateralis muscle during fatiguing isometric contractions J Appl Physiol, July 1, 2005; 99(1): 268 - 280. [Abstract] [Full Text] [PDF]

				D. Farina, L. Arendt-Nielsen, and T. Graven-Nielsen Effect of temperature on spike-triggered average torque and electrophysiological properties of low-threshold motor units J Appl Physiol, July 1, 2005; 99(1): 197 - 203. [Abstract] [Full Text] [PDF]

				D. Farina, L. Arendt-Nielsen, and T. Graven-Nielsen Spike-triggered average torque and muscle fiber conduction velocity of low-threshold motor units following submaximal endurance contractions J Appl Physiol, April 1, 2005; 98(4): 1495 - 1502. [Abstract] [Full Text] [PDF]

				D. Farina, L. Arendt-Nielsen, and T. Graven-Nielsen Experimental muscle pain reduces initial motor unit discharge rates during sustained submaximal contractions J Appl Physiol, March 1, 2005; 98(3): 999 - 1005. [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]

				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]

				D. Farina, L. Arendt-Nielsen, R. Merletti, and T. Graven-Nielsen Effect of Experimental Muscle Pain on Motor Unit Firing Rate and Conduction Velocity J Neurophysiol, March 1, 2004; 91(3): 1250 - 1259. [Abstract] [Full Text] [PDF]

				A. Adam and C. J. De Luca Recruitment Order of Motor Units in Human Vastus Lateralis Muscle Is Maintained During Fatiguing Contractions J Neurophysiol, November 1, 2003; 90(5): 2919 - 2927. [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]

				J. Z. Liu, Z. Y. Shan, L. D. Zhang, V. Sahgal, R. W. Brown, and G. H. Yue Human Brain Activation During Sustained and Intermittent Submaximal Fatigue Muscle Contractions: An fMRI Study J Neurophysiol, July 1, 2003; 90(1): 300 - 312. [Abstract] [Full Text] [PDF]

				S. K. Hunter, R. Lepers, C. J. MacGillis, and R. M. Enoka Activation among the elbow flexor muscles differs when maintaining arm position during a fatiguing contraction J Appl Physiol, June 1, 2003; 94(6): 2439 - 2447. [Abstract] [Full Text] [PDF]

				S. K. Hunter and R. M. Enoka Changes in muscle activation can prolong the endurance time of a submaximal isometric contraction in humans J Appl Physiol, January 1, 2003; 94(1): 108 - 118. [Abstract] [Full Text] [PDF]

				S. K. Hunter, D. L. Ryan, J. D. Ortega, and R. M. Enoka Task Differences With the Same Load Torque Alter the Endurance Time of Submaximal Fatiguing Contractions in Humans J Neurophysiol, December 1, 2002; 88(6): 3087 - 3096. [Abstract] [Full Text] [PDF]