Effects of Reciprocal Ia Inhibition on Contraction Intensity of Co-contraction

Abstract

Introduction: Excessive co-contraction interferes with smooth joint movement. One mechanism is the failure of reciprocal inhibition against antagonists during joint movement. Reciprocal inhibition has been investigated using joint torque as an index of intensity during co-contraction. However, contraction intensity as an index of co-contraction intensity has not been investigated. In this study, we aimed to evaluate the influence of changes in contraction intensity during co-contraction on reciprocal inhibition.Methods: We established eight stimulus conditions in 20 healthy adult males to investigate the influence of changes in contraction intensity during co-contraction on reciprocal inhibition. These stimulus conditions comprised a conditioning stimulus-test stimulation interval (C–T interval) of -2, 0, 1, 2, 3, 4, or 5 ms plus a test stimulus without a conditioning stimulus (single). Co-contraction of the tibialis anterior and soleus muscles at the same as contraction intensity was examined at rest and at 5, 15, and 30% maximal voluntary contraction (MVC).Results: At 5 and 15% MVC in the co-contraction task, the H-reflex amplitude was significantly decreased compared with single stimulation at a 2-ms C–T interval. At 30% MVC, there was no significant difference compared with single stimulation at a 2-ms C–T interval. At a 5-ms C–T interval, the H-reflex amplitude at 30% MVC was significantly reduced compared with that at rest.Discussion: The findings indicated that during co-contraction, reciprocal Ia inhibition worked at 5 and 15% MVC. Contrary inhibition of reciprocal Ia inhibition did not apparently work at 30% MVC, and presynaptic inhibition (D1 inhibition) might work.

Enhancement of spinal reciprocal inhibition depends on the movement speed and range of repetitive passive movement

“…For the test stimulus, the anode and cathode were located on the upper patella and popliteal area, respectively. M waves were induced in the TA muscle via bipolar stimulation, and the conditioning stimulus was applied along the common peroneal nerve below the fibula head (Hirabayashi, Edama, Kojima, Ito, et al, 2019; Hirabayashi et al., 2018; Mizuno et al., 1971; Nielsen & Kagamihara, 1992; Yamaguchi et al., 2018).…”

“…RI was measured as previously described (Hirabayashi, Edama, Kojima, Ito, et al, 2019; Hirabayashi, Edama, Kojima, Miyaguchi, et al, 2019; Hirabayashi et al., 2018; Mizuno et al., 1971; Yamaguchi et al., 2018). A test stimulus was applied to the dominant (tibial) nerve of the Sol muscle after the conditioning stimulus was delivered to the dominant (common peroneal) nerve of the TA muscle.…”

Local and Non-local Effects of Foam Rolling on Passive Soft Tissue Properties and Spinal Excitability

“…In this study, electrical stimulations were delivered using a constant current stimulator (Isolator SS-104 J: Nihon Kohden Corporation) targeting the tibial nerve using 1-ms pulses. Based on previous researches (Hirabayashi et al, 2018(Hirabayashi et al, , 2020, the tibial nerve was selectively stimulated in a monopolar manner, inducing soleus H-reflex and M waves. The anode was placed on the patella and the cathode on the popliteal fossa overlying the nerve at a position using the electrode (Blue Sensor N, size: 30 × 22 mm), providing the greatest H wave amplitude at the smallest stimulus intensity, which was identified by stimulating the different skin surface sites with relatively low currents.…”

Activation of the Supplementary Motor Areas Enhances Spinal Reciprocal Inhibition in Healthy Individuals

“…RI was measured in the same manner as done in previous studies [ 14 , 16 , 26 , 47 , 48 ]. Sol H-reflex amplitude values were measured after conditioning and test stimuli.…”

“…The intensity of the conditioning stimulus was set to the M-wave threshold (stimulus intensity evoking <100 μV) of TA [ 14 , 17 , 26 ]. Conditioning stimuli were carefully placed so as not to cause peroneal muscle contraction [ 26 , 47 , 48 ]. Because the degree of RI varied with the magnitude of H-reflex [ 49 ], the intensity of test stimuli was set to induce an H-reflex of 15–25% of the maximum amplitude value of the Sol M wave (Mmax).…”