Voluntary and electromyostimulation forces in trained and untrained men

Hortobágyi, Tibor; Lambert, N. J.; Tracy, Chad R.; Shinebarger, M. H.

doi:10.1249/00005768-199206000-00013

Cited by 21 publications

(26 citation statements)

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“…Second, we have shown that the nature of the in vivo speed torque relation for the QF is comparable when muscle actions are evoked by EMS vs. voluntary effort and that these relations are similar to those found for affected skeletal muscle in clinically complete spinal cord-injured patients or skeletal muscle in situ or in vitro (19). Third, at least for the tetanic superimposition technique, EMS actually decreases voluntary force (25). Greenhaff et al (23) have demonstrated that glycogen loss occurs in both type I and II fibers during EMS (50 Hz, 1.6-s/1.6-s duty cycle), suggesting that both fiber types are stimulated.…”

Section: Discussionsupporting

confidence: 66%

Vastus lateralis fatigue alters recruitment of musculus quadriceps femoris in humans

Akima

Foley

Prior³

et al. 2002

Journal of Applied Physiology

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. Vastus lateralis fatigue alters recruitment of musculus quadriceps femoris in humans. J Appl Physiol 92: 679-684, 2002; 10.1152/ japplphysiol.00267.2001.-This study tested the hypothesis that fatigue of a single member of musculus quadriceps femoris (QF) would alter use of the other three muscles during knee extension exercise (KEE). Six men performed KEE with the left QF at a load equal to 50% of the 4 ϫ 10 repetitions maximum. Subsequently, electromyostimulation (EMS), intended to stimulate and fatigue the left m. vastus lateralis (VL), was applied for 30 min. Immediately after EMS, subjects repeated the KEE. Transverse relaxation time (T2)-weighted magnetic resonance images were taken before and after each bout of KEE and at 3 and 30 min of EMS to assess use and stimulation, respectively, of the QF. T2 of each of the QF muscles was increased 8-13% after the first KEE. During EMS, T2 increased (P Ͻ 0.05) even more in VL (10%), whereas it decreased (P Ͻ 0.05) to pre-KEE levels in m. vastus medials (VM) and m. rectus femoris (RF). The VL and, to some extent, the m. vastus intermedius were stimulated, whereas the VM and RF were not, thereby recovering from the first bout of KEE. Isometric torque, initially 30% of maximal voluntary, was reduced to 13% at 3 min and 7% at 30 min. T2 was greater (P Ͻ 0.05) after the second than the first bout of KEE, especially the increase for the VM and RF. These results suggest that subjects were able to perform the second bout with little contribution of the VL by greater use of the other QF muscles. The simplest explanation is increased central command to the QF such that the intended act could be accomplished despite acute fatigue of one of its synergists.

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Section: Discussionsupporting

confidence: 66%

Vastus lateralis fatigue alters recruitment of musculus quadriceps femoris in humans

Akima

Foley

Prior³

et al. 2002

Journal of Applied Physiology

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“…FCR and FCU were simultaneously stimulated for 5 s with a 1-s on-ramp and 0 s off-ramp at 2 kHz modulated at 50 Hz up to maximal stimulator output of 80 mA. Such stimulation parameters can produce forces up to 100% MVC with relatively little discomfort in arm muscles (Hortobágyi et al 1992). Pilot experiments revealed that stimulation producing 50% maximal wrist flexion altered the H-reflex on the contralateral side and to minimize subject discomfort, this level of evoked force was used.…”

Section: Studymentioning

confidence: 99%

Changes in Segmental and Motor Cortical Output With Contralateral Muscle Contractions and Altered Sensory Inputs in Humans

Hortobágyi

Taylor

Petersen

et al. 2003

Journal of Neurophysiology

252

204

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. Changes in segmental and motor cortical output with contralateral muscle contractions and altered sensory inputs in humans. J Neurophysiol 90: 2451-2459, 2003; 10.1152/jn.01001.2002. Motor or sensory activity in one arm can affect the other arm. We tested the hypothesis that a voluntary contraction can affect the motor pathway to the contralateral homologous muscle and investigated whether alterations in sensory input might mediate such effects. Responses to transcranial magnetic stimulation [motor-evoked potentials (MEPs)], stimulation of the descending tracts [cervicomedullary MEPs (CMEPs)], and peripheral nerve stimulation (H-reflex) were recorded from the relaxed right flexor carpi radialis (FCR), while the left arm underwent unilateral interventions (5 s duration) that included voluntary contraction, muscle contraction evoked through percutaneous stimulation, tendon vibration, and cutaneous and mixed nerve stimulation. During moderate to strong voluntary wrist flexion on the left, MEPs in the right FCR increased, CMEPs were unaffected, and the H-reflex was depressed. These results are consistent with an increase in excitability of the motor cortex, no effect on the motoneuron pool, and presynaptic inhibition of Ia afferents. In contrast, percutaneous muscle stimulation facilitated both MEPs and the H-reflex. However, muscle contraction produced by a combination of voluntary effort and electrical stimulation also reduced the contralateral H-reflex. After voluntary contractions, the H-reflex remained depressed for 35 s, but after stimulationevoked contractions, it rapidly returned to baseline. Under both conditions, MEPs recovered rapidly. After voluntary contractions, CMEPs were also depressed for approximately 10 s despite their lack of change during contractions. Wrist tendon vibration (100 Hz) did not affect, and 20-Hz median nerve stimulation or forearm medial cutaneous nerve stimulation mildly facilitated, the H-reflex without affecting MEPs. Voluntary wrist extension, similarly to wrist flexion, increased MEPs and depressed H-reflexes. However, ankle dorsiflexion facilitated the H-reflex akin to the Jendrassik maneuver. These data suggest that a unilateral voluntary muscle contraction has contralateral effects at both cortical and segmental levels and that the segmental effects are not replicated by stimulated muscle contraction or by input from muscle spindles or non-nociceptive cutaneous afferents.

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“…Discomfort was greatest for EMS and least for TMS. 3 This study demonstrates that in familiarized subjects, knowing a stimulus (EMS, PNS or TMS) will occur does not impair maximal force or EMG produced despite differences in discomfort associated with the stimulus modalities. These techniques can be used to investigate central drive and peripheral function, at least for intensities comparable to those employed in the present study.…”

Section: Resultsmentioning

confidence: 65%

“…It has been suggested that stimulus-induced discomfort may impair the ability to produce maximal force [1,3,7]. Button and Behm [1] observed lower knee extensor MVC force with EMS; however, this only occurred in subjects unfamiliar with EMS.…”

Section: Discussionmentioning

confidence: 99%

“…This is not always the case for other muscle groups [9]. In addition to the limits inherent to these techniques [5], it has been suggested [1,3] that using the interpolated twitch technique during maximal voluntary contractions (MVC) may interfere with the ability to produce maximal force due to the associated discomfort; however, both studies only employed EMS. Because delivering other types of stimuli (e.g.…”

Section: Introductionmentioning

confidence: 99%

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Anticipation of magnetic and electrical stimuli does not impair maximal voluntary force production

Peyrard

Sawh

Fan

et al. 2016

Neuroscience Letters

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Voluntary and electromyostimulation forces in trained and untrained men

Cited by 21 publications

References 0 publications

Vastus lateralis fatigue alters recruitment of musculus quadriceps femoris in humans

Vastus lateralis fatigue alters recruitment of musculus quadriceps femoris in humans

Changes in Segmental and Motor Cortical Output With Contralateral Muscle Contractions and Altered Sensory Inputs in Humans

Anticipation of magnetic and electrical stimuli does not impair maximal voluntary force production

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