The Effects of Circumferential Air-Splint Pressure on Flexor Carpi Radialis H-Reflex in Subjects without Neurological Deficits

Abstract

The purposes of this study were to investigate the effects of circumferential pressure on flexor carpi radialis (FCR) H-reflex in subjects without neuromuscular deficits and to evaluate the skin's contribution to this effect. FCR H-reflex was assessed in 43 subjects by measuring the peak-to-peak amplitude change before, during, and after circumferential pressure was applied to the forearm. Twelve H-reflexes (H/M ratio: M = 25%, SD = 14) were recorded before pressure application to obtain a baseline value (H(baseline)) to which all data were compared. A pneumatic 15 to 20-cm air splint inflated to 51-60 mmHg provided the pressure around the forearm. H-reflex recordings were taken at 1, 3, and 5 min. during (H(pressure)) and after pressure application. A second smaller study (placebo), in which the air splint was inflated to 0 mmHg, was conducted in 5 subjects to ensure that changes in reflex amplitudes were not a result of cutaneous effects. Two types of responses were observed in the FCR H-reflex following pressure application. One group of subjects significantly increased in H-reflex amplitude while another group decreased in H-reflex amplitude when compared to H(baseline). Regression analysis found that H(max) explained 37.2% of the variance when controlling for H(baseline). Subjects with larger H(max) showed an increase in H(pressure) while subjects with lower H(max) showed decreases in H(pressure) The placebo study revealed no differences in H-reflex amplitude from baseline values, implying that skin stimulation from the air splint has no role in the effects observed. The dichotomous result indicates that pressure influences the upper extremity differently than it does the lower extremity in certain individuals. Clinicians, using circumferential pressure as a therapeutic modality to lower muscle activity of the upper extremity, need to be cognizant that pressure may have contrasting effects on their patients.

Effect of Air-Splint Pressure on the Soleus Stretch Reflex during a Voluntary Ramp Plantar Flexion

“…4). A change in the SSR amplitude was defined as having a >10% change from the baseline values [16].…”

“…Agostinucci et al [16] suggested that Golgi tendon organs (GTOs) may be partly responsible for the H reflex variability in the flexor carpi radialis when CP was applied around the forearm. They argued that GTOs are not just simple predictable pathways with a single function but have rather variable effects depending on the task performed, the muscle activated, and the inputs from other neuronal systems [32][33][34][35].…”

“…Finally, investigations looking at the effect of circumferential pressure (CP) on MNRE have been mostly conducted on a resting muscle [5,6,16]. It is well known that when an H reflex is superimposed on a muscle contraction resulting in a limb movement, the H-reflex amplitude increases dramatically before and during the voluntary contraction of the homologous muscle [17].…”

The effects of circumferential pressure on the soleus muscle F-wave in healthy subjects

“…Since motoneurons are recruited in an orderly way from smallest too largest (size principle), it has been suggested that H-reflexes primarily assess the excitability of the smaller motoneurons that innervate slow twitch muscle fibers (Fisher, 1992(Fisher, , 1996Guiloff and Modarres-Sadeghi, 1991). Agostinucci et al (2006) alluded to the size principle as a possible explanation for the dichotomus results observed in the Flexor Carpi Radials H-reflex amplitude during CP in people without neurological disorders. The authors suggested the morphology of the Flexor Carpi Radials is more heterogenous than its lower limb counterpart and thus may respond differently to CP depending upon the ratio of slow to fast twitch muscle fibers within in the muscle.…”

Inhibitory Effects of Circumferential Pressure on Flexor Carpi Radialis H-Reflex in Adults with Neurological Deficits

“…It was suggested the mechanism of action was spinal in origin since the group with spinal cord injury responded similarly to participants who had no neurological deficits (Robichaud & Agostinucci, 1996). Agostinucci, Holmberg, Mushen, Plisko, and Gofman (2006), in an analogous study, looked at the effect circumferential pressure had on the upper limb flexor carpi radialis muscle in a group without neurological deficit. Analyses showed a mean decrease in H-reflex amplitude; however, in approximately half of the participants, H-reflex facilitation occurred.…”