David F Collins

David F Collins
University of Alberta | UAlberta · Centre for Neuroscience

About

94
Publications
12,431
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4,692
Citations
Citations since 2016
16 Research Items
1867 Citations
2016201720182019202020212022050100150200250300
2016201720182019202020212022050100150200250300
2016201720182019202020212022050100150200250300
2016201720182019202020212022050100150200250300

Publications

Publications (94)
Article
Full-text available
PurposeNeuromuscular electrical stimulation (NMES) is often delivered at frequencies that recruit motor units (MUs) at unphysiologically high rates, leading to contraction fatigability. Rotating NMES pulses between multiple electrodes recruits subpopulations of MUs from each site, reducing MU firing rates and fatigability. This study was designed t...
Article
Full-text available
The use of upper limb vibration (ULV) during exercise and rehabilitation continues to gain popularity as a modality to improve function and performance. Currently, a lack of knowledge of the pathways being altered during ULV limits its effective implementation. Therefore, the aim of this study was to investigate whether indirect ULV modulates trans...
Preprint
Full-text available
Purpose: Neuromuscular electrical stimulation (NMES) recruits motor units (MUs) at unphysiologically high rates, leading to contraction fatigability. Rotating NMES pulses between multiple electrodes recruits different MUs from each site, reducing MU firing rates and fatigability. This study aimed to determine whether rotating pulses between an incr...
Preprint
Full-text available
The aim of this study was to investigate whether indirect upper limb vibration (ULV) modulates transmission along spinal and corticospinal pathways that control the human forearm. All measures were assessed under CONTROL (no vibration) and ULV (30 Hz; 0.4 mm displacement) conditions while participants maintained a small contraction of the right fle...
Article
Full-text available
This study compared the differences in neural and muscular mechanisms related to explosive torque in chronically strength‐trained young and older men (>5 years). Fifty‐four participants were allocated into four groups according to age and strength training level: older untrained (n=14; 65.6±2.9 years), older trained (n=12; 63.6±3.8 years), young un...
Article
This study was designed to assess the effects of acute exercise on performance of a paired associate learning (PAL) test, an operationalization of hippocampal-dependent associative memory. Participants performed a PAL test and then ran on a treadmill (exercise group, n = 52) or solved Sudoku puzzles (control group, n = 54). Participants returned 2,...
Article
Introduction: Interleaved neuromuscular electrical stimulation (iNMES) involves alternating stimulus pulses between the tibialis anterior muscle and common peroneal nerve. Purpose: The current investigation aimed to characterize the relationship between contraction amplitude, motor unit (MU) "overlap" and contraction fatigability during iNMES. I...
Article
Full-text available
PURPOSE: To understand the effects of long-term strength training in the neural and contractile properties of explosive force in young adults and elders. METHODS: 54 healthy males were divided in four groups: untrained young control (YC - n=14; 26 ± 4 yrs), untrained elder control (EC - n=14; 66 ± 3 yrs), strength trained young (YT - n=14; 27 ± 3 y...
Article
Neuromuscular electrical stimulation (NMES) is used to produce contractions to restore movement and reduce secondary complications for individuals experiencing motor impairment. NMES is conventionally delivered through a single pair of electrodes over a muscle belly or nerve trunk using short pulse durations and frequencies between 20-40 Hz (conven...
Article
Full-text available
Background: The benefits of neuromuscular electrical stimulation (NMES) for rehabilitation depend on the capacity to generate functionally relevant torque with minimal fatigability and discomfort. Traditionally, NMES is delivered either over a muscle belly (mNMES) or nerve trunk (nNMES). Recently, we developed a technique that minimizes contraction...
Article
Introduction: Neuromuscular electrical stimulation (NMES) over a muscle belly (mNMES) recruits superficial motor units (MUs) preferentially, while NMES over a nerve trunk (nNMES) recruits MUs evenly throughout the muscle. We tested whether "interleaving" pulses between the mNMES and nNMES sites (iNMES) reduces the fatigability of contractions for...
Article
Introduction: In this study we quantified the "overlap" between motor units recruited by single pulses of neuromuscular electrical stimulation (NMES) delivered over the tibialis anterior muscle (mNMES) and the common fibular nerve (nNMES). We then quantified the torque produced when pulses were alternated between the mNMES and nNMES sites at 40 Hz...
Article
Full-text available
Introduction: Neuromuscular electrical stimulation (NMES) can be delivered over a muscle belly (mNMES) or nerve trunk (nNMES). Both methods generate contractions that fatigue rapidly due, in part, to non-physiologically high motor unit (MU) discharge frequencies. We introduce interleaved NMES (iNMES), whereby stimulus pulses are alternated between...
Article
Full-text available
Motoneurons receive a barrage of inputs from descending and reflex pathways. Much of our understanding about how these inputs are transformed into motor output in humans has come from recordings of single motor units during voluntary contractions. This approach, however, is limited because the input is ill-defined. Herein, we quantify the discharge...
Article
Full-text available
Sensorimotor control is greatly affected by two factors—the time it takes for an animal to sense and respond to stimuli (responsiveness), and the ability of an animal to distinguish between sensory stimuli and generate graded muscle forces (resolution). Here, we demonstrate that anatomical limitations force a necessary trade-off between responsiven...
Article
Full-text available
The afferent volley generated by neuromuscular electrical stimulation (NMES) influences corticospinal (CS) excitability and frequent NMES sessions can strengthen CS pathways, resulting in long-term improvements in function. This afferent volley can be altered by manipulating NMES parameters. Presently, we manipulated one such parameter, pulse durat...
Article
Introduction: Neuromuscular electrical stimulation (NMES) over a muscle belly (mNMES) generates contractions predominantly through M-waves, while NMES over a nerve trunk (nNMES) can generate contractions through H-reflexes in people who are neurologically intact. We tested whether the differences between mNMES and nNMES are present in people with...
Article
OBJECTIVE: To compare the spatial distribution of motor units recruited in tibialis anterior (TA) when electrical stimulation is applied over the TA muscle belly versus the common peroneal nerve trunk. METHODS: Electromyography (EMG) was recorded from the surface and from fine wires in superficial and deep regions of TA. Separate M-wave recruitment...
Article
Objective: The aim of this study was to quantify, for the first time, H-reflexes evoked during prolonged trains of wide-pulse neuromuscular electrical stimulation (WP-NMES) in individuals with chronic spinal cord injury (SCI). We hypothesised that after the first H-reflex, reflex amplitudes would be depressed (due to post-activation depression), b...
Article
Neuromuscular electrical stimulation (NMES) increases the excitability of corticospinal (CS) pathways by altering circuits in motor cortex (M1). How NMES affects circuits interposed between the ascending afferent volley and descending CS pathways is not known. Presently, we hypothesized that short-latency afferent inhibition (SAI) would be reduced...
Article
Full-text available
Unilateral training involving voluntary contractions, neuromuscular electrical stimulation (NMES), or a combination of the two can increase the excitability of neural circuits bilaterally within the CNS. Many rehabilitation programs are designed to promote such "neuroplasticity" to improve voluntary movement following CNS damage. While much is know...
Article
Full-text available
Purpose: Damage to the spinal accessory nerve (SAN) can result in denervation of the trapezius muscle in patients undergoing surgery for head and neck cancer. Trapezius denervation leads to muscle weakness and dysfunction that, for some patients, persists despite the return of conduction along the SAN. This prospective case series describes an int...
Article
Neuromuscular electrical stimulation that incorporates wide pulse widths (1ms) and high frequencies (100Hz; wide pulse-NMES (WP-NMES)) augments contractions through an increased reflexive recruitment of motoneurons in individuals without neurological impairments and those with spinal cord injury. The current study was designed to investigate whethe...
Article
Full-text available
Neuromuscular electrical stimulation (NMES) can be delivered over a nerve trunk or muscle belly and both can generate contractions through peripheral and central pathways. Generating contractions through peripheral pathways is associated with a nonphysiological motor unit recruitment order, which may limit the efficacy of NMES rehabilitation. Prese...
Article
Full-text available
Neuromuscular electrical stimulation (NMES) generates contractions by depolarising axons beneath the stimulating electrodes. The depolarisation of motor axons produces contractions by signals travelling from the stimulation location to the muscle (peripheral pathway), with no involvement of the central nervous system (CNS). The concomitant depolari...
Article
Full-text available
H-reflexes are progressively depressed, relative to the first response, at stimulation frequencies above 0.1 Hz (postactivation depression; PAD). Presently, we investigated whether H-reflexes "recover" from this depression throughout 10-s trains of stimulation delivered at physiologically relevant frequencies (5-20 Hz) during functionally relevant...
Article
Full-text available
The afferent volley generated during neuromuscular electrical stimulation (NMES) can increase the excitability of human corticospinal (CS) pathways to muscles of the leg and hand. Over time, such increases can strengthen CS pathways damaged by injury or disease and result in enduring improvements in function. There is some evidence that NMES affect...
Article
Full-text available
Sensorimotor control is greatly affected by two factors--the time it takes for an animal to sense and respond to stimuli (responsiveness), and the ability of an animal to distinguish between sensory stimuli and generate graded muscle forces (resolution). Here, we demonstrate that anatomical limitations force a necessary trade-off between responsive...
Article
Neuromuscular electrical stimulation (NMES) has been shown to generate contractions that include a central recruitment of motoneurons; however, the effect of pulse width on electromyographic (EMG) and torque responses during NMES are not well documented. Soleus EMG and isometric plantarflexion torque were recorded from 14 subjects with NMES deliver...
Article
Full-text available
Neuromuscular electrical stimulation (NMES) can be delivered over a nerve trunk or muscle belly and can generate contractions by activating motor (peripheral pathway) and sensory (central pathway) axons. In the present experiments, we compared the peripheral and central contributions to plantar flexion contractions evoked by stimulation over the ti...
Article
Full-text available
The afferent volley generated during neuromuscular electrical stimulation (NMES) can increase the excitability of the human corticospinal (CS) pathway. This study was designed to determine the effect of different frequencies of NMES applied over the common peroneal nerve on changes in CS excitability for the tibialis anterior (TA) muscle. We hypoth...
Article
We have suggested previously that motor units recruited reflexively contribute to torque produced during neuromuscular electrical stimulation (NMES), but this has not been tested directly. The current experiments were designed to quantify the contributions to twitch torque made by motor units recruited at M-wave and H-reflex latencies. The relation...
Article
Full-text available
The ability to generate torque during a maximum voluntary contraction (MVC) changes over the day. The present experiments were designed to determine the influence of an individual's chronotype on this diurnal rhythm and on cortical, spinal, and peripheral mechanisms that may be related to torque production. After completing a questionnaire to deter...
Article
Full-text available
Reflex pathways connect all four limbs in humans. Presently, we tested the hypothesis that reflexes also link sensory receptors in the lower leg with muscles of the lower back (erector spinae; ES). Taps were applied to the right Achilles' tendon and electromyographic activity was recorded from the right soleus and bilaterally from ES. Reflexes were...
Article
Full-text available
Neuromuscular electrical stimulation (NMES) generates contractions by activation of motor axons (peripheral mechanism), but the afferent volley also contributes by recruiting spinal motoneurons synaptically (central mechanism), which recruits motoneurons according to Henneman's size principle. Thus, we hypothesized that contractions that develop du...
Article
Dynamic hyperinflation and leg muscle fatigue are independently associated with exercise limitation in patients with chronic obstructive pulmonary disease (COPD). The aims of the present study were to examine 1) the relationship between these limitations and 2) the effect of delaying ventilatory limitation on exercise tolerance and leg muscle fatig...
Article
Neuromuscular electrical stimulation can generate contractions through both peripheral and central mechanisms. The peripheral mechanism involves the direct activation of motor axons, while the central mechanism involves the activation of sensory axons that recruit spinal neurons through a reflex pathway. For use in functional electrical stimulation...
Article
Loud sounds can decrease reaction time (RT) and increase force generated during voluntary contractions. Accordingly, we hypothesized that the loud starter's pistol at the Olympic Games allows runners closer to the starter to react sooner and stronger than runners farther away. RT for the 100/110 m athletics events at the 2004 Olympics were obtained...
Article
It has been proposed that pulse-widths of 0.5-1.0 ms should be used to evoke H-reflexes in humans; however, the influence of pulse-width on H-reflex recruitment over a range of stimulus intensities has not been well characterized. We constructed soleus H-reflex vs. M-wave recruitment curves using 50, 200, 500, and 1000 micros pulses in 12 subjects....
Article
Tetanic electrical stimulation applied over human muscle or peripheral nerve generates contractions by depolarizing motor axons beneath the stimulating electrodes. However, the simultaneous depolarization of sensory axons can also contribute to the contractions by the synaptic recruitment of spinal motoneurons. Maximizing this central contribution...
Article
Full-text available
Neuromuscular electrical stimulation can generate contractions through peripheral and central mechanisms. Direct activation of motor axons (peripheral mechanism) recruits motor units in an unnatural order, with fatigable muscle fibers often activated early in contractions. The activation of sensory axons can produce contractions through a central m...
Article
Full-text available
Compound muscle action potentials (CMAPs) recorded using surface electrodes are often used to assess the excitability of neural pathways to skeletal muscle. However, the amplitude of CMAPs can be influenced by changes at the recording site, independent of mechanisms within the central nervous system. We quantified how joint angle and background con...
Article
Tetanic neuromuscular stimulation evokes contractions by depolarizing motor axons beneath the stimulating electrodes. However, we have shown that extra torque can develop due to the discharge of spinal neurons recruited by the evoked sensory volley. The present experiments investigated whether extra torque in the ankle plantar- and dorsiflexors was...
Article
Electrical stimulation (1-ms pulses, 100 Hz) produces more torque than expected from motor axon activation (extra contractions). This experiment investigates the most effective method of delivering this stimulation for neuromuscular electrical stimulation. Surface stimulation (1-ms pulses; 20 Hz for 2 s, 100 Hz for 2 s, 20 Hz for 3 s) was delivered...
Article
Full-text available
Changes in the reflex amplitude throughout the day have been observed in non-human mammals. The present experiment tested whether diurnal fluctuations also occur in humans. Hoffmann reflex (H-reflex) amplitude was measured in soleus and flexor carpi radialis (FCR) muscles from the data collected over a 12-h period between 7:00-9:00 a.m. and 7:00-9:...
Article
Full-text available
Humans perform rhythmic, locomotor movements with the arms and legs every day. Studies using reflexes to probe the functional role of the CNS suggest that spinal circuits are an important part of the neural control system for rhythmic arm cycling and walking. Here, by studying motor-evoked potentials (MEPs) in response to transcranial magnetic stim...
Article
Full-text available
The neural mechanisms underlying the sense of joint position and movement remain controversial. While cutaneous receptors are known to contribute to kinesthesia for the fingers, the present experiments test the hypothesis that they contribute at other major joints. Illusory movements were evoked at the interphalangeal (IP) joints of the index finge...
Article
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In humans, the flexor carpi radialis (FCR) and extensor carpi radialis (ECR) muscles act as antagonists during wrist flexion-extension and as functional synergists during radial deviation. In contrast to the situation in most antagonist muscle pairs, Renshaw cells innervated by the motor neurons of each muscle inhibit the motoneurons, but not Ia in...
Article
Full-text available
The amplitudes and signs of cutaneous reflexes are modulated during rhythmic movements of the arms and legs (during walking and arm or leg cycling for instance). This reflex modulation is frequently independent of the background muscle activity and may involve central pattern generator (CPG) circuits. The purpose of the present study was to investi...
Article
Full-text available
Neural connections between the cervical and lumbosacral spinal cord may assist in arm and leg coordination during locomotion. Currently the extent to which arm activity can modulate reflex excitability of leg muscles is not fully understood. We showed recently that rhythmic arm movement significantly suppresses soleus H-reflex amplitude probably vi...
Article
Full-text available
There is extensive modulation of cutaneous and H-reflexes during rhythmic leg movement in humans. Mechanisms controlling reflex modulation (e.g., phase- and task-dependent modulation, and reflex reversal) during leg movements have been ascribed to the activity of spinal central pattern generating (CPG) networks and peripheral feedback. Our working...
Article
Full-text available
Percutaneous electrical stimulation over tibialis anterior and triceps surae was performed in 14 patients with traumatic spinal cord injury (SCI) to look for evidence that 'extra contractions' can develop, beyond those due to activation of the motor axons beneath the stimulating electrodes. Criteria for the extra contractions included marked asymme...
Article
Full-text available
During locomotor tasks such as walking, running, and swimming, the arms move rhythmically with the legs. It has been suggested that connections between the cervical and lumbosacral spinal cord may mediate some of this interlimb coordination. However, it is unclear how these interlimb pathways modulate reflex excitability during movement. We hypothe...
Article
Full-text available
Percutaneous electrical stimulation over tibialis anterior and triceps surae was performed in 14 patients with traumatic SCI to look for evidence that increased force can develop, beyond that due to activation of the motor axons beneath the stimulating electrodes. Criteria for the increased force included marked asymmetry of force with respect to s...