Locomotor-Like Leg Movements Evoked by Rhythmic Arm Movements in Humans

Abstract

Motion of the upper limbs is often coupled to that of the lower limbs in human bipedal locomotion. It is unclear, however, whether the functional coupling between upper and lower limbs is bi-directional, i.e. whether arm movements can affect the lumbosacral locomotor circuitry. Here we tested the effects of voluntary rhythmic arm movements on the lower limbs. Participants lay horizontally on their side with each leg suspended in an unloading exoskeleton. They moved their arms on an overhead treadmill as if they walked on their hands. Hand-walking in the antero-posterior direction resulted in significant locomotor-like movements of the legs in 58% of the participants. We further investigated quantitatively the responses in a subset of the responsive subjects. We found that the electromyographic (EMG) activity of proximal leg muscles was modulated over each cycle with a timing similar to that of normal locomotion. The frequency of kinematic and EMG oscillations in the legs typically differed from that of arm oscillations. The effect of hand-walking was direction specific since medio-lateral arm movements did not evoke appreciably leg air-stepping. Using externally imposed trunk movements and biomechanical modelling, we ruled out that the leg movements associated with hand-walking were mainly due to the mechanical transmission of trunk oscillations. EMG activity in hamstring muscles associated with hand-walking often continued when the leg movements were transiently blocked by the experimenter or following the termination of arm movements. The present results reinforce the idea that there exists a functional neural coupling between arm and legs.

Activation of interlimb interactions increases the motor output in legs of healthy subjects: Study under the conditions of arm and leg unloading

“…2a, 2b, 6a, 6b). These results, like the data obtained by other authors [12,18,23,24], show the activation of coupling between the cervical and lumbosacral levels of regulation of upper and lower limb movements depending on both central com mands and intersegmental interactions. In passive movements, the influence of central commands is sup posed to be weaker [25], whereas peripheral feedback coupled with limb movements is similar during passive and active arm movements [28,29].…”

“…It may be suggested that what occurs on the interneurons of the lumbar spinal cord is inte gration of the proprioceptive inputs from moving arms and vibrated leg muscles, which even under the sub threshold vibration conditions, promotes in the acti vation of stepping automatism. The effect obtained can be compared with the influence of stepping arm movements on the activation of the leg central pattern generator reported by Sylos Labini et al [23]. How ever, in this study, the proprioceptive inflow from mov ing arms was substantially stronger as the arms moved with the treadmill band support.…”

“…Rhythmic swinging like arm movements during walking and running also exert a noticeable modulating effect on the electrical activ ity of leg muscles (electromyography, EMG) during standing [22]. It has been shown recently that, in the recumbent posture under leg unloading conditions, the stepping like arm movements on the treadmill band can even initiate stepping leg movements [23]. This strong dynamic coupling was confirmed by Gerasimenko et al [3], who showed that transcutane ous electrical stimulation of the spinal cord at the cer vical level significantly facilitated involuntary stepping induced by the same stimulation of the lumbosacral division of the spinal cord.…”

Lower extremity muscle activation and function in progressive task-oriented training on the supplementary tilt table during stepping-like movements in patients with acute stroke hemiparesis

“…The maximum muscle activation value obtained in each of the three attempts was used to calculate the MVC. Also, EMG envelopes were assumed to be zero if the maximum value was less than 3 lV, which was considered to be the noise level (Solopova et al, 2011a,b;Sylos-Labini et al, 2014). These data were exported as text data into a custom-written Microsoft Excel program to determine the metric for measuring muscle activation: the ratio of muscle activation during steppinglike movements on the tilt table to that at the normal grade of MMT (% MVC).…”

The Spark of Life: Engaging the Cortico‐Truncoreticulo‐Propriospinal Pathway by Electrical Stimulation

“…Both CPGs display facilitatory interlimb neural coupling via propriospinal connections, as in quadrupedal animals . Importantly, voluntary rhythmic arm movements increase leg muscle recruitment during submaximal recumbent stepping , modulate leg muscle activity during standing , and can even evoke stepping‐like leg movements . Solopova et al have shown that peripheral sensory stimulation (continuous muscle vibration) and central tonic activation (postcontraction state of neuronal networks following a long‐lasting isometric voluntary effort, that is, Kohnstamm phenomenon) can evoke nonvoluntary rhythmic arm movements in human subjects, but also nonvoluntary rhythmic arm movements together with rhythmic movements of legs.…”