Task-related variations in the surface EMG of the human first dorsal interosseous muscle.

Evidence from human and animal studies suggests that motor neuron pool organization is not uniform for all motor tasks. Groupings of motor units within a muscle may be recruited differentially for a given task based on principles beyond anatomical or architectural features of the muscle alone. This study aimed to determine whether: (1) there was differential activation across locations of the first dorsal interosseous (FDI) muscle during a given task, (2) the differential activation was related to directional requirements and/or end goal of the task, and (3) there was an anatomical pattern to the differential activation.

Soleus H-reflex modulation after motor incomplete spinal cord injury: effects of body position and walking speed.

Objective: To examine position-dependent (semireclined to standing) and walking speed-dependent soleus H-reflex modulation after motor incomplete spinal cord injury (SCI).

Participants: Twenty-six patients with motor incomplete SCI (mean: 45 +/- 15 years) and 16 noninjured people (mean: 38 +/- 14 years).

Methods: Soleus H-reflexes were evoked by tibial nerve stimulation.

Reliability of soleus H-reflexes in standing and walking post-incomplete spinal cord injury.

Objective: To establish the reliability of soleus H-reflex in individuals with incomplete spinal cord injury (SCI) during the standing and the swing and stance phases of overground walking.

Methods: Fourteen SCI (40 +/- 10 years) and eight noninjured subjects (32 +/- 9 years) participated. The noninjured and SCI subjects walked at self-selected speed overground.

Comparison of single bout effects of bicycle training versus locomotor training on paired reflex depression of the soleus H-reflex after motor incomplete spinal cord injury.

Objective: To examine paired reflex depression changes post 20-minute bout each of 2 training environments: stationary bicycle ergometer training (bicycle training) and treadmill with body weight support and manual assistance (locomotor training).

Design: Pretest-posttest repeated-measures.

Setting: Locomotor laboratory.

Soleus H-reflex modulation and paired reflex depression from prone to standing and from standing to walking.

Patterns of soleus H-reflex modulation as a function of posture, task, and reflex activation history were assessed with three experimental paradigms: lying prone compared with standing unsupported; standing compared with the initiation of walking; and standing compared with the mid stance phase of walking. Paired H-reflexes, 80 ms apart, were evoked under each condition. The paired reflex depression (PRD), the percentage depression of the second H-reflex relative to the first H-reflex, was modulated independently of the first H-reflex across the postures and tasks.

Sural nerve evoked responses in human hip and ankle muscles while standing.

The objective of this study was to investigate the influence of background EMG, as manipulated by changes in limb loading, and electrical stimulus intensity on sural nerve evoked EMG responses in proximal hip (ipsilateral gluteus medius and contralateral adductor longus) and distal ankle (ipsilateral soleus) muscles during quiet standing. We studied 14 healthy subjects who were instructed to stand on a force platform and load the right leg to 20, 30, 60, and 80% body weight. Trains of stimuli were delivered to the right sural nerve at three different intensities (1.

Relationship between muscle length and moment arm on EMG activity of human triceps surae muscle.

Purpose: The purpose of this experiment was to evaluate the effects of both muscle length and moment arm (MA) on the electromyographic (EMG) and force output of the triceps surae (TS) muscle.

Relevance: It is well recognized that changes in muscle length affect both the muscle's force generating capacity as well as its twitch speed. This relationship is well established in animal preparations.