Role of vision and task complexity on soleus H-reflex gain

Pınar, Salih; Kitano, Koichi; Koceja, David M.

doi:10.1016/j.jelekin.2009.03.002

Cited by 33 publications

(34 citation statements)

References 25 publications

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“…In agreement with the literature [14,15], the asymptomatic subjects, regardless of the footwear condition, decreased their H-reflex gain when balancing on an unstable surface as compared to balancing on a stable surface. Only while wearing their custom-molded foot orthotics did subjects with musculoskeletal disorders appropriately decrease the gain of the gastrocnemius H-reflex from balancing on a stable surface to an unstable surface.…”

Section: Discussionsupporting

confidence: 91%

“…(Refer to Figure 7). balance during challenging tasks [14,15,20,[35][36][37][38]. The custom-molded foot orthotics by increasing the detection of plantar pressures under the foot, e.g., improved arch support, would evoke cutaneous reflexes to enhance the resolution of somatosensory reflexes contributing to the neuromuscular control of balance [1][2][3].…”

Section: Discussionmentioning

confidence: 99%

“…During single leg balance tasks, either increasing surface compliance (more unstable) or removing visual information decreases the electromyographic (EMG) amplitudes of the tibial nerve H-reflex response in healthy adults [14,15]. Evoking H-reflexes during single leg balance tasks provides an indirect, but valid assessment of sensorimotor integration mechanisms underlying the neuromuscular control of balance [16,17].…”

Section: Introductionmentioning

confidence: 99%

“…Changes in sensorimotor integration mechanisms underlying the neuromuscular control of balance are expressed as the modulation of H-reflex gain ( Hreflex amplitude/ background EMG activity). From a functional perspective, attenuation of H-reflex gain prevents the saturation of spinal reflex pathways and postural oscillations from disrupting neuromuscular control of posture, balance, and voluntary movements [14][15][16][17][18][19][20]. Evidence is emerging to suggest that the ability to appropriately modulate H-reflex gain is a causal factor regulating postural sway parameters, e.g., the ability to decrease tibial nerve H-reflex gain reduces postural sway during balance and postural tasks [21][22][23][24].…”

Section: Introductionmentioning

confidence: 99%

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Effects of Footwear Comfort Perception on the Neuromuscular Control of Balance

Burke

2012

International Journal of Neuroscience

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The purpose of this research was to determine the effects of footwear comfort perception on the gain of the gastrocnemius H-reflex response during single leg balance tasks. Subjects performed single leg balance tasks while wearing aerobic sneakers with two different pairs of shoe insoles that were subjectively rated for comfort using a reliable 150 mm visual analog scale. The primary outcome was the consistency of decreasing the gain of the gastrocnemius H-reflex with increasing balance task complexity as a function of footwear comfort perception. Among the asymptomatic subjects (n = 11), H-reflex gain significantly decreased by 19% and 10% from balancing on a stable surface to an unstable surface for the shoe-brand and replacement insoles, respectively (p < .05). Among the subjects with musculoskeletal disorders (n = 13), H-reflex gain significantly decreased by 10% from balancing on a stable surface to an unstable surface when wearing custom-molded foot orthotics, but H-reflex gain significantly increased by 27% from balancing on a stable surface to an unstable surface when wearing replacement insoles (p < .05). Decreases in footwear comfort perception may negatively impact the attenuation of gastrocnemius H-reflex gain that contributes to the neuromuscular control of challenging balance tasks.

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Section: Discussionsupporting

confidence: 91%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effects of Footwear Comfort Perception on the Neuromuscular Control of Balance

Burke

2012

International Journal of Neuroscience

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“…This is often termed reflex task dependence. For example, reflex amplitudes are higher during dynamic movement compared with matched isometric contractions (Baudry et al 2010;Baudry and Enoka 2009;Bawa and Sinkjaer 1999), and the afferent gain was observed to increase in parallel with the instability of a dynamic task (Pinar et al 2010). In this study, we hypothesized that these task-dependent changes in the magnitude of the afferent input to motor neurons reflect a deliberate strategy of the CNS: when a task is performed in an unstable environment, the afferent gain is high to minimize the impact of external perturbations at the expense of the risk of motor system resonance.…”

mentioning

confidence: 98%

The optimal neural strategy for a stable motor task requires a compromise between level of muscle cocontraction and synaptic gain of afferent feedback

Dideriksen

Negro

Farina

2015

Journal of Neurophysiology

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Dideriksen JL, Negro F, Farina D. The optimal neural strategy for a stable motor task requires a compromise between level of muscle cocontraction and synaptic gain of afferent feedback. J Neurophysiol 114: 1895-1911, 2015. First published July 22, 2015 doi:10.1152/jn.00247.2015.-Increasing joint stiffness by cocontraction of antagonist muscles and compensatory reflexes are neural strategies to minimize the impact of unexpected perturbations on movement. Combining these strategies, however, may compromise steadiness, as elements of the afferent input to motor pools innervating antagonist muscles are inherently negatively correlated. Consequently, a high afferent gain and active contractions of both muscles may imply negatively correlated neural drives to the muscles and thus an unstable limb position. This hypothesis was systematically explored with a novel computational model of the peripheral nervous system and the mechanics of one limb. Two populations of motor neurons received synaptic input from descending drive, spinal interneurons, and afferent feedback. Muscle force, simulated based on motor unit activity, determined limb movement that gave rise to afferent feedback from muscle spindles and Golgi tendon organs. The results indicated that optimal steadiness was achieved with low synaptic gain of the afferent feedback. High afferent gains during cocontraction implied increased levels of common drive in the motor neuron outputs, which were negatively correlated across the two populations, constraining instability of the limb. Increasing the force acting on the joint and the afferent gain both effectively minimized the impact of an external perturbation, and suboptimal adjustment of the afferent gain could be compensated by muscle cocontraction. These observations show that selection of the strategy for a given contraction implies a compromise between steadiness and effectiveness of compensations to perturbations. This indicates that a task-dependent selection of neural strategy for steadiness is necessary when acting in different environments.

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Neural control of joint stability during a ballistic force production task

Holl

Zschorlich

2011

Exp Brain Res

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Changes in transmission in Ia afferent and corticospinal pathways have been reported to depend on various factors including task complexity and the phase of movement. Here, we test whether a unilateral voluntary force production task leads to specific changes in both Ia afferent (by the use of the H-reflex technique) and corticospinal (by the use of transcranial magnetic stimulation, TMS) pathways in response to different mechanical conditions. The participants were exposed to either one or three mechanical degrees of freedom (DoF) of an external object while performing a unilateral knee extension movement in a sitting posture. The amplitudes of the m. soleus (SOL) EMG to either type of stimulation were normalized to amplitudes obtained during voluntary tonic contractions at matched background EMG in order to assess movement-related alterations. The results at two phases during movement (initial phase and during task execution) were analyzed. The unstable 1 DoF condition led to elevated co-contraction of SOL and the tibialis anterior muscle. Phase- and movement-related modulations of muscle responses to both types of stimulation were present in both mechanical conditions. However, the stable 1 DoF condition caused a significant facilitation of normalized H-reflexes in the initial phase of movement as compared to 3 DoF (1 DoF: 206%, 3 DoF: 96%, P < 0.001). Conversely, larger normalized amplitudes in response to TMS were found in the initial phase of the 3 DoF condition as compared to 1 DoF (1 DoF: 107%, 3 DoF 160%, P < 0.001). Additionally, during task execution the normalized amplitudes of TMS and H-Reflex testing revealed a relative decrease when compared to the initial phase of movement. It is suggested that presynaptic mechanisms caused the changes in the normalized H-reflexes (and thus in Ia afferent transmission) and that altered normalized responses to TMS reflect changes in corticospinal transmission. Consequently, we reason that the transmission in both pathways is sensitive to the nature of the mechanical interaction and thus to biomechanical task demands. Finally, the voluntary nature of the task might have caused a decisive influence of anticipatory control mechanisms triggered by advance information about the modality of environmental dynamics.

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Role of vision and task complexity on soleus H-reflex gain

Cited by 33 publications

References 25 publications

Effects of Footwear Comfort Perception on the Neuromuscular Control of Balance

Effects of Footwear Comfort Perception on the Neuromuscular Control of Balance

The optimal neural strategy for a stable motor task requires a compromise between level of muscle cocontraction and synaptic gain of afferent feedback

Neural control of joint stability during a ballistic force production task

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