A pilot study to measure upper extremity H-reflexes following neuromuscular electrical stimulation therapy after stroke

Abstract

Upper extremity (UE) hemiparesis persists after stroke, limiting hand function. Neuromuscular electrical stimulation (NMES) is an effective intervention to improve UE recovery, although the underlying mechanisms are not fully understood. Our objective was to establish a reliable protocol to measure UE agonist–antagonist forearm monosynaptic reflexes in a pilot study to determine if NMES improves wrist function after stroke. We established the between-day reliability of the H-reflex in the extensor carpi radialis longus (ECRL) and flexor carpi radialis (FCR) musculature for individuals with prior stroke (n = 18). The same-day generation of ECRL/FCR H-reflex recruitment curves was well tolerated, regardless of age or UE spasticity. The between-day reliability of the ECRL H-reflex was enhanced above FCR, similar to healthy subjects [20], with the Hmax the most reliable parameter quantified in both muscles. H-reflex and functional measures following NMES show the potential for NMES-induced increases in ECRL Hmax, but confirmation requires a larger clinical study. Our initial results support the safe, easy, and efficacious use of in-home NMES, and establish a potential method to measure UE monosynaptic reflexes after stroke.

Acute Neuromuscular Adaptation at the Spinal Level Following Middle Cerebral Artery Occlusion-Reperfusion in the Rat

“…The H-reflex, obtained before exercise, was not modified by cerebral ischemia. This result was in agreement with a previous study on humans in which no difference of the extensor carpi radialis longus and flexor carpi radialis H-reflex in resting condition was detected after stroke injury [ 19 ] . Other study showed an opposite result by measuring an increase in H-reflex after stroke injury [ 18 ] .…”

“…The motor reflex regulation at the spinal level is recognized as an important aspect of the motor control and may be modulated by cerebral ischemia, despite the fact that controversial results remain for the upper-extremity control in human studies [ 16 ] – [ 19 ] . The Hoffmann reflex (H-reflex) has often been used in preclinical human and animal studies to explore the spinal sensorimotor adaptation during and/or after skeletal muscle activity [ 20 ] , [ 21 ] .…”

The H-reflex as an important indicator in kinesiology

“…The most commonly assessed muscles of the lower limbs that display the H-reflex are the soleus muscle [37][38][39][40] and the gastrocnemius muscle [5,41,42]. While the H-reflex is very difficult to observe in the upper limbs, some researchers have shown that it can be induced for the flexor carpi radialis muscle [43][44][45][46][47] and the extensor carpi radialis muscle [43,46].…”

“…The H-reflex is frequently measured to assess the monosynaptic reflex in, among others, stroke patients [47] and healthy persons who do not engage in sport [39,55]. Researchers have also observed that sport training may affect the parameters of the H-reflex; hence, a growing number of studies in the literature are being conducted among athletes engaged in endurance sports [37], as well as in speed and strength sports [5,41].…”

Upper-extremity spinal reflex inhibition is reproducible and strongly related to grip force poststroke

“…While reflex inhibition has been used to assess rehabilitation effects [8], these findings were reported without information regarding its stability over time. Reproducibility of the FCR H-reflex latency, amplitude [14,15], and slope of the H-and Mwaves has been reported in healthy controls and persons poststroke [16,17], but the reliability of FCR H-reflex inhibition has not been established in either population.…”