Major role for sensory feedback in soleus EMG activity in the stance phase of walking in man

Sinkjær, Thomas; Andersen, Jacob Buus; Ladouceur, Michel; Christensen, L. O. D.; Nielsen, Jens Bo

doi:10.1111/j.1469-7793.2000.00817.x

Cited by 268 publications

(244 citation statements)

References 46 publications

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“…Although modest, the reported plastic changes indicate that after spinal cord injury, load pathways would have a larger contribution in the control of stance if trained regularly and together with pharmacological intervention. Our results support previous reports that load receptors may contribute to the activation of leg extensors during walking in humans (Ghori and Luckwill, 1985;Dietz et al, 1992;Stephens and Yang, 1999;Sinkjaer et al, 2000;Stein et al, 2000). For example, it was proposed that afferent inputs from receptors signaling contact forces during the stance phase are essential for the activation of spinal locomotor centers in SCI subjects (Harkema et al, 1997).…”

Section: Discussionsupporting

confidence: 82%

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Spinal Cats on the Treadmill: Changes in Load Pathways

2003

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Treadmill training and clonidine, an ␣-2 noradrenergic agonist, have been shown to improve locomotion after spinal cord injury. We speculate that transmission in load pathways, which are involved in body support during stance, is specifically modified by training. This was evaluated by comparing two groups of spinal cats; one group (n ϭ 11) was trained to walk until full-weight-bearing (3-4 weeks), and the other (shams; n ϭ 7) was not. During an acute experiment, changes in group I pathways, monosynaptic excitation, disynaptic inhibition, and polysynaptic excitation were investigated by measuring the response amplitude in extensor motoneurons before and after clonidine injection. Monosynaptic excitation was not modified by clonidine but was decreased significantly by training. Disynaptic inhibition was significantly decreased by clonidine in both groups, but more significantly in trained cats, and significantly reduced by training after clonidine. Also, clonidine could reverse group IB inhibition into polysynaptic excitation in both groups but more frequently in trained cats. We also investigated whether fictive stepping revealed additional changes. In trained cats, the phase-dependent modulation of all three responses was similar to patterns reported previously, but in shams, modulation of monosynaptic and polysynaptic responses was not. Overall, training appears to decrease monosynaptic excitation and enhance the effects of clonidine in the reduction of disynaptic inhibition and reversal to polysynaptic excitation. Because it is believed that polysynaptic excitatory group I pathways transmit locomotor drive to extensor motoneurons, we suggest that the latter changes would facilitate the recruitment of extensor muscles for recovering weight-bearing during stepping.

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Section: Discussionsupporting

confidence: 82%

“…The monosynaptic stretch reflex is thought to make a major contribution to the level of EMG activities during stepping (Stein et al, 2000), although this role in humans was questioned previously (Sinkjaer et al, 2000). Clonidine did not affect the amplitude of monosynaptic EPSP significantly (Fig.…”

Section: Training and Clonidinementioning

confidence: 93%

Spinal Cats on the Treadmill: Changes in Load Pathways

2003

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“…4C, c). The sign and latency of these EMG changes are consistent with an unloading response (Sinkjaer et al 2000). We also observed an increase in ECR activity with lag of 484.8 Ϯ 118.3 ms (range: 387-675 ms; Fig.…”

Section: R E S U L T Ssupporting

confidence: 64%

Neural and Electromyographic Correlates of Wrist Posture Control

Suminski

Rao

Mosier

et al. 2007

Journal of Neurophysiology

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Suminski AJ, Rao SM, Mosier KM, Scheidt RA. Neural and electromyographic correlates of wrist posture control. J Neurophysiol 97: 1527Neurophysiol 97: -1545Neurophysiol 97: , 2007. First published November 29, 2006; doi:10.1152/jn.01160.2006. In identical experiments in and out of a MR scanner, we recorded functional magnetic resonance imaging and electromyographic correlates of wrist stabilization against constant and time-varying mechanical perturbations. Positioning errors were greatest while stabilizing random torques. Wrist muscle activity lagged changes in joint angular velocity at latencies suggesting trans-cortical reflex action. Drift in stabilized hand positions gave rise to frequent, accurately directed, corrective movements, suggesting that the brain maintains separate representations of desired wrist angle for feedback control of posture and the generation of discrete corrections. Two patterns of neural activity were evident in the blood-oxygenation-level-dependent (BOLD) time series obtained during stabilization. A cerebello-thalamo-cortical network showed significant activity whenever position errors were present. Here, changes in activation correlated with moment-by-moment changes in position errors (not force), implicating this network in the feedback control of hand position. A second network, showing elevated activity during stabilization whether errors were present or not, included prefrontal cortex, rostral dorsal premotor and supplementary motor area cortices, and inferior aspects of parietal cortex. BOLD activation in some of these regions correlated with positioning errors integrated over a longer timeframe consistent with optimization of feedback performance via adjustment of the behavioral goal (feedback setpoint) and the planning and execution of internally generated motor actions. The finding that nonoverlapping networks demonstrate differential sensitivity to kinematic performance errors over different time scales supports the hypothesis that in stabilizing the hand, the brain recruits distinct neural systems for feedback control of limb position and for evaluation/adjustment of controller parameters in response to persistent errors.

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“…Tension of the stabilization straps caused the subjects' knees to be 2-3°more valgus than the knee position during typical standing; however, the change in position with the straps was equal in both groups, and therefore its influence should have been equivalent in both groups. Further research is needed to measure muscle stiffness to confirm its relationship to muscle responsiveness, but greater preactivation of the medial quadriceps and hamstring muscles could be an effective adaptation for minimizing instability through increased muscle stiffness (35)(36)(37).…”

Section: Discussionmentioning

confidence: 99%

Knee stabilization in patients with medial compartment knee osteoarthritis

Lewek¹,

Ramsey²,

Snyder‐Mackler³

et al. 2005

Arthritis & Rheumatism

113

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Objective. Individuals with medial knee osteoarthritis (OA) experience knee laxity and instability. Strategies aimed at muscle stabilization may influence the long-term integrity of the joint. This study sought to determine how individuals with medial knee OA respond to a rapid valgus knee movement, to investigate the relationship between muscle-stabilization strategies and knee instability.Methods. Twenty-one subjects with medial knee OA and genu varum and 19 control subjects were tested. Subjects stood with the test limb on a movable platform, comprising a plate that translated laterally to rapidly stress the knee's medial periarticular structures and create a potentially destabilizing sensation at the knee joint. Knee motion and muscle responses were recorded. Subjects rated the condition of their knee with a selfreport questionnaire about knee instability during daily activities.Results. Prior to plate movement, the OA subjects demonstrated more medial muscle co-contraction than did controls (P‫؍‬ 0.014). Following plate movement, the OA subjects shifted less weight off the test limb (P ‫؍‬ 0.013) and had greater medial co-contraction (P ‫؍‬ 0.037). OA subjects without knee instability had higher co-contraction of the vastus medialis medial hamstrings than did those who reported having instability that affected their daily activities (P ‫؍‬ 0.038). More knee stability correlated positively with higher co-contraction of the vastus medialis medial hamstrings prior to plate movement (r ‫؍‬ 0.459, P ‫؍‬ 0.042).Conclusion. Individuals with medial knee OA attempt to stabilize the knee with greater co-contraction of the medial muscle in response to laxity that appears on the medial side of the joint only. This strategy presumably contributes to higher joint compression and could exacerbate joint destruction, and therefore needs to be altered to slow or stop the progression of the OA disease process.

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Major role for sensory feedback in soleus EMG activity in the stance phase of walking in man

Cited by 268 publications

References 46 publications

Spinal Cats on the Treadmill: Changes in Load Pathways

Spinal Cats on the Treadmill: Changes in Load Pathways

Neural and Electromyographic Correlates of Wrist Posture Control

Knee stabilization in patients with medial compartment knee osteoarthritis

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