Neuromechanical interactions between the limbs during human locomotion: an evolutionary perspective with translation to rehabilitation.

During bipedal locomotor activities, humans use elements of quadrupedal neuronal limb control. Evolutionary constraints can help inform the historical ancestry for preservation of these core control elements support transfer of the huge body of quadrupedal non-human animal literature to human rehabilitation. In particular, this has translational applications for neurological rehabilitation after neurotrauma where interlimb coordination is lost or compromised.

Adaptation of cutaneous stumble correction when tripping is part of the locomotor environment.

We recently showed that cutaneous reflexes evoked by stimulating the superficial peroneal (SP; innervates foot dorsum) nerve are modulated according to the level of postural threat. Context-related modulation was observed mainly in contralateral (c) responses but not in the ipsilateral responses. This lack of effect on ipsilateral (i) cutaneous reflexes might have been caused by the general nature of the whole body perturbation.

Context-dependent modulation of interlimb cutaneous reflexes in arm muscles as a function of stability threat during walking.

Cutaneous reflexes evoked in the muscles of the arms with electrical stimulation of nerves of the foot ("interlimb reflexes") are observed during walking. These reflexes have been suggested to coordinate the actions of the legs and arms when walking is disturbed. Recently, we showed that cutaneous reflexes evoked in the leg muscles after stimulation at the foot are modulated according to the level of postural threat during walking.

Postural uncertainty leads to dynamic control of cutaneous reflexes from the foot during human walking.

Cutaneous reflexes evoked by stimulation of nerves innervating the foot are modulated in a phase-dependent manner during locomotion. The pattern of modulation of these reflexes has been suggested to indicate a functional role of cutaneous reflexes in assisting to maintain stability during walking. We hypothesized that if cutaneous reflexes assist in maintaining stability during gait, then these reflexes should be modulated in a context-dependent manner when subjects are asked to walk in an environment in which stability is challenged.

Possible contributions of CPG activity to the control of rhythmic human arm movement.

There is extensive modulation of cutaneous and H-reflexes during rhythmic leg movement in humans. Mechanisms controlling reflex modulation (e.g.

Coordinated interlimb compensatory responses to electrical stimulation of cutaneous nerves in the hand and foot during walking.

It has been shown that stimulation of cutaneous nerves innervating the hand (superficial radial, SR) and foot (superficial peroneal, SP) elicit widespread reflex responses in many muscles across the body. These interlimb reflex responses were suggested to be functionally relevant to assist in motor coordination between the arms and legs during motor tasks such as walking. The experiments described in this paper were conducted to test the hypothesis that interlimb reflexes were phase-dependently modulated and produced functional kinematic changes during locomotion.

Modulation of cutaneous reflexes in arm muscles during walking: further evidence of similar control mechanisms for rhythmic human arm and leg movements.

Stimulation of cutaneous nerves innervating the hand evokes prominent reflexes in many arm muscles during arm cycling. We hypothesized that the mechanisms controlling reflex modulation during the rhythmic arm swing of walking would be similar to that documented during arm cycling. Thus, we expected cutaneous reflexes to be modulated by position in the walking cycle (phase dependence) and be different when walking compared to contraction while standing (task dependence).