Changes in H reflex and neuromechanical properties of the trapezius muscle after 5 weeks of eccentric training: a randomized controlled trial.
Trapezius muscle Hoffman (H) reflexes were obtained to investigate the neural adaptations induced by a 5-wk strength training regimen, based solely on eccentric contractions of the shoulder muscles. Twenty-nine healthy subjects were randomized into an eccentric training group (n = 15) and a reference group (n = 14). The eccentric training program consisted of nine training sessions of eccentric exercise performed over a 5-wk period. H-reflex recruitment curves, the maximal M wave (Mmax), maximal voluntary contraction (MVC) force, rate of force development (RFD), and electromyographic (EMG) voluntary activity were recorded before and after training. H reflexes were recorded from the middle part of the trapezius muscle by electrical stimulation of the C3/4 cervical nerves; Mmax was measured by electrical stimulation of the accessory nerve. Eccentric strength training resulted in significant increases in the maximal trapezius muscle H reflex (Hmax) (21.4% [5.5-37.3]; P = 0.01), MVC force (26.4% [15.0-37.7]; P < 0.01), and RFD (24.6% [3.2-46.0]; P = 0.025), while no significant changes were observed in the reference group. Mmax remained unchanged in both groups. A significant positive correlation was found between the change in MVC force and the change in EMG voluntary activity in the training group (r = 0.57; P = 0.03). These results indicate that the net excitability of the trapezius muscle H-reflex pathway increased after 5 wk of eccentric training. This is the first study to investigate and document changes in the trapezius muscle H reflex following eccentric strength training.
Center for Sensory-Motor Interaction, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark; and.
Steffen
S
Vangsgaard
Neuroscience Research Australia and the University of New South Wales, Sydney, Australia.
Janet L
JL
Taylor
Center for Sensory-Motor Interaction, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark; and.
Ernst A
EA
Hansen
Center for Sensory-Motor Interaction, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark; and pm@hst.aau.dk.
Pascal
P
Madeleine
D000222:Adaptation, Physiological / Q000502:physiology; D000328:Adult; D004558:Electric Stimulation / Q000379:methods; D015444:Exercise / Q000502:physiology; D005260:Female; D005528:Foot / Q000502:physiology; D006181:H-Reflex / Q000502:physiology*; D006801:Humans; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D055070:Resistance Training / Q000379:methods; D012782:Shoulder / Q000502:physiology; D064171:Superficial Back Muscles / Q000502:physiology*; D055815:Young Adult
human; monosynaptic reflex; shoulder; strength training