Electrical cutaneous stimulation of the foot sole does not enhance rate of torque development during maximal effort isometric plantarflexion in females.

Rate of torque development (RTD) measures how rapidly one can generate torque and is crucial for balance and athletic performance. Fast RTD depends on the rapid recruitment of high threshold motor units (MUs). Cutaneous electrical stimulation has been shown to alter MU excitability, favoring high threshold MUs via reduced recruitment thresholds.

Pressure-Induced Microvascular Reactivity With Whole Foot Loading Is Unique Across the Human Foot Sole.

Background: Foot sole plantar pressure generates transient but habitual cutaneous ischemia, which is even more exacerbated in atypical gait patterns. Thus, adequate post-occlusive reactive hyperaemia (PORH) is necessary to maintain skin health. Plantar pressure regional variance during daily tasks potentially generates region-specific PORH, crucial for ischemic defence.

Mechanoreceptor sensory feedback is impaired by pressure induced cutaneous ischemia on the human foot sole and can predict cutaneous microvascular reactivity.

Introduction: The foot sole endures high magnitudes of pressure for sustained periods which results in transient but habitual cutaneous ischemia. Upon unloading, microvascular reactivity in cutaneous capillaries generates an influx of blood flow (PORH: post-occlusive reactive hyperemia). Whether pressure induced cutaneous ischemia from loading the foot sole impacts mechanoreceptor sensitivity remains unknown.

Vestibular input modulates stepping balance reactions early in the pre-step phase through to post-recovery.

Compensatory stepping reactions to recover balance are frequently performed, however, the role of sensory feedback in regulating these responses is not fully understood. Specifically, it is unknown whether vestibular input influences compensatory stepping. Here, we aimed to assess whether step responses utilize vestibular input by combining medio-lateral galvanic vestibular stimulation (GVS) with step-inducing balance perturbations via unpredictable anterior-posterior platform translations.

Neuromechanical characterization of the abductor hallucis and its potential role in upright postural control.

There is growing evidence to support a role for the abductor hallucis (AH) in standing balance control; however, functional properties of the muscle that may provide more insight into AH's specific contribution to upright posture have yet to be characterized. This study was conducted to quantify functional neuromechanical properties of the AH and correlate the measures with standing balance variables. We quantified strength and voluntary activation during maximal voluntary isometric contractions of the great toe abductor in nine (3 females and 6 males) healthy, young participants.

Heating the skin on the foot sole enhances cutaneous reflexes in the lower limb.

Cutaneous input is important in postural control and balance. Aging and diabetes impair skin sensitivity and motor control. Heat application can improve skin sensation, but its influence on motor control remains unknown.

Calf cutaneous stimulation generates reflexes in the thigh that can be modified by subthreshold noisy vibration.

Imperceptible tactile noise applied to the skin of the feet enhances posture-correcting cutaneous reflexes. This sensory augmentation technique, stochastic resonance (SR), has not been tested in the less-sensitive hairy skin of the leg for its reflex-enhancement ability. The objectives of this study were to determine whether calf skin stimulation produces cutaneous reflexes and whether noise can modify the reflex.

Modeling foot sole cutaneous afferents: FootSim.

While walking and maintaining balance, humans rely on cutaneous feedback from the foot sole. Electrophysiological recordings reveal how this tactile feedback is represented in neural afferent populations, but obtaining them is difficult and limited to stationary conditions. We developed the FootSim model, a realistic replication of mechanoreceptor activation in the lower limb.

Heating the Skin Over the Knee Improves Kinesthesia During Knee Extension.

To determine how heating affects dynamic joint position sense at the knee, participants (n = 11; F = 6) were seated in a HUMAC NORM dynamometer. The leg was passively moved through extension and flexion, and participants indicated when the 90° reference position was perceived, both at baseline (28.74 ± 2.

Location-specific cutaneous electrical stimulation of the footsole modulates corticospinal excitability to the plantarflexors and dorsiflexors during standing.

Non-noxious electrical stimulation to distinct locations of the foot sole evokes location-specific cutaneous reflex responses in lower limb muscles. These reflexes occur at latencies that may enable them to be mediated via a transcortical pathway. Corticospinal excitability to the plantarflexors and dorsiflexors was measured in 16 participants using motor evoked potentials (MEPs).

Remote Subthreshold Stimulation Enhances Skin Sensitivity in the Lower Extremity.

Foot sole skin interfaces with the ground and contributes to successful balance. In situations with reduced sensitivity in the glabrous foot skin, stochastic resonance (SR) improves skin sensitivity by adding tactile noise. Some situations, however, involve an interface comprised of hairy skin, which has higher thresholds for sensitivity.

Exploring the effect of capsaicin-induced central sensitization on the upper limb nociceptive withdrawal reflex threshold.

The nociceptive withdrawal reflex (NWR) threshold is commonly employed in the lower limb to assess clinical and experimentally induced pain. However, no studies to date have investigated changes in spinal nociception in the upper limb, via the NWR threshold, following experimentally induced central sensitization (CS). We tested the hypothesis that experimentally induced CS of the C5-C6 spinal segment significantly reduces NWR thresholds in muscles of the upper limb.

The immediate effects of foot orthosis geometry on lower limb muscle activity and foot biomechanics.

Foot orthoses (FOs) are used to treat clinical conditions by altering the external forces applied to the foot and thereafter the forces of muscles and tendons. However, whether specific geometric design features of FOs affect muscle activation is unknown. The aim of this study was to investigate if medial heel wedging and increased medial arch height have different effects on the electromyography (EMG) amplitude of tibialis posterior, other muscles of the lower limb and the kinematics and kinetics at the rearfoot and ankle.

The Anatomical Distribution of Mechanoreceptors in Mouse Hind Paw Skin and the Influence of Integrin α1β1 on Meissner-Like Corpuscle Density in the Footpads.

Afferent neurons and their mechanoreceptors provide critical sensory feedback for gait. The anatomical distribution and density of afferents and mechanoreceptors influence sensory feedback, as does mechanoreceptor function. Electrophysiological studies of hind paw skin reveal the different types of afferent responses and their receptive fields, however, the anatomical distribution of mechanoreceptor endings is unknown.

Cutaneous tactile sensitivity before and after tail loss and regeneration in the leopard gecko ().

Amongst tetrapods, mechanoreceptors on the feet establish a sense of body placement and help to facilitate posture and biomechanics. Mechanoreceptors are necessary for stabilizing the body while navigating through changing terrains or responding to a sudden change in body mass and orientation. Lizards such as the leopard gecko () employ autotomy - a voluntary detachment of a portion of the tail - to escape predation.

Subthreshold Electrical Noise Applied to the Plantar Foot Enhances Lower-Limb Cutaneous Reflex Generation.

Reflex responses generated by cutaneous mechanoreceptors of the plantar foot are important for the maintenance of balance during postural tasks and gait. With aging, reflex generation, particularly from fast adapting type I receptors, is reduced, which likely contributes to impaired postural stability in this population. Therefore, improving reflex generation from these receptors may serve as a tool to improve balance performance.

Foot sole cutaneous stimulation mitigates neuromuscular fatigue during a sustained plantar flexor isometric task.

Neuromuscular fatigue impairs motor coordination, movement stability, and proprioception, which further decreases performance. A neuromechanical coupling exists between foot sole cutaneous mechanoreceptors and motoneurons of the lower limb, however, the contribution of skin sensory input on muscle fatigue remains unclear. The purpose of this study was to determine if the presence of cutaneous stimulation could mitigate the effect of fatigue of the plantar flexor muscles during a sustained isometric task at 30% maximal voluntary contraction (MVC).

A systematic review of the effect of footwear, foot orthoses and taping on lower limb muscle activity during walking and running.

Background: External devices are used to manage musculoskeletal pathologies by altering loading of the foot, which could result in altered muscle activity that could have therapeutic benefits.

Objectives: To establish if evidence exists that footwear, foot orthoses and taping alter lower limb muscle activity during walking and running.

Study Design: Systematic literature review.

Can texture change joint position sense at the knee joint in those with poor joint position accuracy?

Skin contributes to joint position sense (JPS) at multiple joints. Altered cutaneous input at the foot can modulate gait and balance and kinesiology tape can enhance proprioception at the knee, but its effect may be dependent on existing capacity. The effect of texture at the knee, particularly in those with poor proprioception, is unknown.

Visual feedback is not necessary for recalibrating the vestibular contribution to the dynamic phase of a perturbation recovery response.

Our recent work demonstrated that vision can recalibrate the vestibular signal used to re-establish equilibrium following a platform perturbation. Here, we investigate whether vision provided during a platform perturbation can recalibrate the use of vestibular reafference during the dynamic phase of the perturbation response. Dynamic postural responses were examined during a series of five forward perturbations to the body, while galvanic vestibular stimulation (GVS) selectively altered vestibular feedback and LCD occlusion spectacles controlled visual availability.

Effects of foot position on skin structural deformation.

As the largest and most superficial organ, the skin is well positioned for receiving sensory information from the environment. It is conceivable that changes in posture could result in deformations of the skin and subsequent changes in skin material properties. Specifically, the ankle and metatarsophalangeal joints have the capability to undergo large postural alterations with the potential to induce large structural deformations in the skin of the foot.

Physiological and cognitive measures during prolonged sitting: Comparisons between a standard and multi-axial office chair.

Prolonged sitting, common in many workplaces, reduces blood flow to the lower limb and has negative health outcomes. CoreChair is an active-sitting chair that encourages increased movement to help mitigate these outcomes. Physiological and cognitive measures were recorded in ten subjects over 4 h of sitting in both the CoreChair and a traditional office chair.

The between-day reliability of peroneus longus EMG during walking.

The peroneus longus (PL) is a rearfoot evertor, important in frontal plane foot motion. Studying PL function has been limited by previous electromyography (EMG) studies reporting poor between-day reliability. Due to its close proximity to adjacent muscles, EMG measures of PL may be susceptible to crosstalk, thus correct electrode placement is vital.

Central contributions to torque depression: an antagonist perspective.

Torque depression (TD) is the reduction in steady-state isometric torque following active muscle shortening when compared to an isometric reference contraction at the same muscle length and activation level. Central nervous system excitability differs in the TD state. While torque production about a joint is influenced by both agonist and antagonist muscle activation, investigations of corticospinal excitability have focused on agonist muscle groups.