Different strategies to compensate for the effects of fatigue revealed by neuromuscular adaptation processes in humans

Bonnard, Mireille; Sirin, A.V.; Oddsson, Lars; Thorstensson, Alf

doi:10.1016/0304-3940(94)90850-8

Cited by 105 publications

(72 citation statements)

References 11 publications

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“…When fatigue occurred during hopping activities, the participants relied on proportionally greater knee muscles compared to ankle muscles to accomplish the movements (Bonnard et al, 1994). During repetitive weightlifting, subjects tended to compensate for fatigue by decreasing the knee and hip extensor muscles while increasing the trunk motion (Sparto et al, 1997).…”

Section: Discussionmentioning

confidence: 99%

Shifting of activation center in the brain during muscle fatigue: An explanation of minimal central fatigue?

et al. 2007

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Accumulating evidence suggests that the overall level of cortical activation controlling a voluntary motor task that leads to significant muscle fatigue does not decrease as much as the activation level of the motoneuron pool projecting to the muscle. One possible explanation for this "muscle fatigue>cortical fatigue" phenomenon is that the brain is an organ with built-in redundancies: it has multiple motor centers and parallel pathways, and the center of activation may shift from one location to another when neurons in the previous location become fatigued. This hypothesis was tested by estimating the changes of source locations of high-density (64 channels) scalp electroencephalographic (EEG) signals collected during both fatigue and non-fatigue motor tasks. A current dipole model was used to estimate the EEG sources. The fatigue motor task induced significant muscle fatigue, and the non-fatigue task did not. The EEG signal source that indicated the center of brain activation showed substantial location shifts during the fatigue motor task. The shifts could not be explained by variations of source locations caused by error estimated from the non-fatigue task EEG and simulated data. Compared to the non-fatigue condition, the weightedcenter of the source locations for all the participants shifted toward the right hemisphere (ipsilateral to the muscle activation), anterior, and inferior cortical regions under the fatigue condition. Fatigue did not alter dipole (source-signal) strength or the overall level of brain activation. The brain may avoid fatigue by shifting neuron populations that participate in a fatiguing motor task.

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Section: Discussionmentioning

confidence: 99%

Shifting of activation center in the brain during muscle fatigue: An explanation of minimal central fatigue?

et al. 2007

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“…Such a pattern may represent a compensatory strategy to maintain leg stiffness during impact movements. 40 …”

Section: Preactivationmentioning

confidence: 99%

Muscle Coactivation Before and After the Impact Phase of Running Following Isokinetic Fatigue

Kellis

Zafeiridis

Amiridis

2011

Journal of Athletic Training

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Context: The effects of fatigue on impact loading during running are unclear, with some authors reporting increased impact forces and others reporting decreased forces.Objective: To examine the effects of isokinetic fatigue on muscle cocontraction ratios about the knee and ankle during running.Design: Cross-sectional study. Setting: Neuromechanics laboratory.Patients or Other Participants: Female middle-distance runners (age 5 21.3 6 1.93 years) with at least 5 years of training experience.Intervention(s): Participants ran on the treadmill at 3.61 m/s before and immediately after the fatigue protocol, which consisted of consecutive, concentric knee extension-flexion at 1206/s until they could no longer produce 30% of the maximum knee-extension moment achieved in the familiarization session for 3 consecutive repetitions.Main Outcome Measure(s): Electromyographic (EMG) amplitude of the vastus medialis (VM), biceps femoris (BF), gastrocnemius (GAS), and tibialis anterior (TA) was recorded using surface electrodes. Agonist:antagonist EMG ratios for the knee (VM:BF) and ankle (GAS:TA) were calculated for the preactivation (PR), initial loading response (LR 1 ), and late loading response (LR 2 ) phases of running. Hip-, knee-, and ankle-joint angular displacements at initial foot contact were obtained from 3-dimensional kinematic tracings.Results: Fatigue did not alter the VM:BF EMG ratio during the PR phase (P . .05), but it increased the ratio during the LR 1 phase (P , .05). The GAS:TA EMG ratio increased during the LR 1 phase after fatigue (P , .05) but remained unchanged during the PR and LR 2 phrases (P . .05).Conclusions: The increased agonist EMG activation, coupled with reduced antagonist EMG activation after impact, indicates that the acute decrease in muscle strength capacity of the knee extensors and flexors results in altered muscleactivation patterns about the knee and ankle before and after foot impact.Key Words: biomechanics, muscle fatigue, joint stability Key PointsN After an isokinetic fatigue protocol for the knee-extensor and knee-flexor muscles, participants contacted the ground with a greater knee-flexion angle.N An antagonist inhibition strategy about the knee and ankle was noted, as was a quadriceps-dominant strategy during the preactivation and initial contact phases of running.

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“…For instance, several studies have reported alternating levels of muscle activity among synergist muscles during low-level submaximal isometric exercises (Kouzaki and Shinohara, 2006;Kouzaki et al, 2002). Other authors reported changes in muscle coordination during a dynamic task such as pedaling (Billaut et al, 2005;Dorel et al, 2009), hopping (Bonnard et al, 1994) or vertical jump (Rodacki et al, 2002). Although some of these studies reported modest changes (Dorel et al, 2009;Rodacki et al, 2002), others reported more important changes in both muscle activity level and muscle activity profile (Bonnard et al, 1994).…”

Section: Introductionmentioning

confidence: 99%

Fatigue-related adaptations in muscle coordination during a cyclic exercise in humans

Turpin

Guével

Durand

et al. 2011

Journal of Experimental Biology

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SUMMARYMuscle fatigue is an exercise-induced reduction in the capability of a muscle to generate force. A possible strategy to counteract the effects of fatigue is to modify muscle coordination. We designed this study to quantify the effect of fatigue on muscle coordination during a cyclic exercise involving numerous muscles. Nine human subjects were tested during a constant-load rowing exercise (mean power output: 217.9±32.4W) performed until task failure. The forces exerted at the handle and the footstretcher were measured continuously and were synchronized with surface electromyographic (EMG) signals measured in 23 muscles. In addition to a classical analysis of individual EMG data (EMG profile and EMG activity level), a non-negative matrix factorization algorithm was used to identify the muscle synergies at the start and the end of the test. Among the 23 muscles tested, 16 showed no change in their mean activity level across the rowing cycle, five (biceps femoris, gluteus maximus, semitendinosus, trapezius medius and vastus medialis) showed a significant increase and two (gastrocnemius lateralis and longissimus) showed a significant decrease. We found no change in the number of synergies during the fatiguing test, i.e. three synergies accounted for more than 90% of variance accounted for at the start (92.4±1.5%) and at the end (91.0±1.8%) of the exercise. Very slight modifications at the level of individual EMG profiles, synergy activation coefficients and muscle synergy vectors were observed. These results suggest that fatigue during a cyclic task preferentially induces an adaptation in muscle activity level rather than changes in the modular organization of the muscle coordination.

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Different strategies to compensate for the effects of fatigue revealed by neuromuscular adaptation processes in humans

Cited by 105 publications

References 11 publications

Shifting of activation center in the brain during muscle fatigue: An explanation of minimal central fatigue?

Shifting of activation center in the brain during muscle fatigue: An explanation of minimal central fatigue?

Muscle Coactivation Before and After the Impact Phase of Running Following Isokinetic Fatigue

Fatigue-related adaptations in muscle coordination during a cyclic exercise in humans

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