TY - JOUR

T1 - Interlimb communication to the knee flexors during walking in humans

AU - Stevenson, Andrew James Thomas

AU - Geertsen, Svend Sparre

AU - Andersen, Jacob Buus

AU - Sinkjær, Thomas

AU - Nielsen, Jens Bo

AU - Mrachacz-Kersting, Natalie

N1 - CURIS 2013 NEXS 169

PY - 2013

Y1 - 2013

N2 - A strong coordination between the two legs is important for maintaining a symmetric gait pattern and adapting to changes in the external environment. In humans as well as animals, receptors arising from the quadriceps muscle group influence the activation of ipsilateral muscles. Moreover, strong contralateral spinal connections arising from quadriceps and hamstrings afferents have been shown in animal models. Therefore, the aims of the present study were to assess if such connections also exist in humans and to elucidate on the possible pathways. Contralateral reflex responses were investigated in the right leg following unexpected unilateral knee joint rotations during locomotion in either the flexion or extension direction. Strong reflex responses in the contralateral biceps femoris (cBF) muscle with a mean onset latency of 76 ± 6 ms were evoked only from ipsilateral knee extension joint rotations in the late stance phase. To investigate the contribution of a transcortical pathway to this response, transcranial magnetic (TMS) and electrical (TES) stimulation were applied. Motor evoked potentials (MEPs) elicited by TMS, but not TES, were facilitated when elicited at the time of the cBF response to a greater extent than the algebraic sum of the cBF reflex and MEPs elicited separately, indicating that a transcortical pathway likely contributes to this interlimb reflex. The cBF reflex response may therefore be integrated with other sensory input, allowing for more flexible responses. We hypothesize that the cBF reflex response may be a preparation of the contralateral leg for early load bearing, slowing the forward progression of the body in order to maintain dynamic equilibrium during walking.

AB - A strong coordination between the two legs is important for maintaining a symmetric gait pattern and adapting to changes in the external environment. In humans as well as animals, receptors arising from the quadriceps muscle group influence the activation of ipsilateral muscles. Moreover, strong contralateral spinal connections arising from quadriceps and hamstrings afferents have been shown in animal models. Therefore, the aims of the present study were to assess if such connections also exist in humans and to elucidate on the possible pathways. Contralateral reflex responses were investigated in the right leg following unexpected unilateral knee joint rotations during locomotion in either the flexion or extension direction. Strong reflex responses in the contralateral biceps femoris (cBF) muscle with a mean onset latency of 76 ± 6 ms were evoked only from ipsilateral knee extension joint rotations in the late stance phase. To investigate the contribution of a transcortical pathway to this response, transcranial magnetic (TMS) and electrical (TES) stimulation were applied. Motor evoked potentials (MEPs) elicited by TMS, but not TES, were facilitated when elicited at the time of the cBF response to a greater extent than the algebraic sum of the cBF reflex and MEPs elicited separately, indicating that a transcortical pathway likely contributes to this interlimb reflex. The cBF reflex response may therefore be integrated with other sensory input, allowing for more flexible responses. We hypothesize that the cBF reflex response may be a preparation of the contralateral leg for early load bearing, slowing the forward progression of the body in order to maintain dynamic equilibrium during walking.

U2 - 10.1113/jphysiol.2013.257949

DO - 10.1113/jphysiol.2013.257949

M3 - Journal article

C2 - 23918771

VL - 591

SP - 4921

EP - 4935

JO - The Journal of Physiology

JF - The Journal of Physiology

SN - 0022-3751

IS - 19

ER -