Background Recent evidence has suggested that corticospinal excitability alterations are present in the surrounding ankle musculature in individuals with chronic ankle instability (CAI). However, there is limited support for the effect of CAI on corticospinal excitability of the tibialis anterior (TA) muscle, specifically. Traditional corticospinal excitability measurements are performed in a less functional, seated position. However, it is suggested that corticospinal excitability measures may depend on changes in body positions and the type of task. Assessing corticospinal excitability of the TA during a more dynamic task may reveal corticospinal deficits not observed in seated assessments.
Objective To examine differences in corticospinal excitability and inhibitory mechanisms of the TA in seated and single leg balance positions.
Design Single-blinded; case-control.
Setting Research laboratory.
Participants Twelve participants with CAI (2 male, 10 female; age = 20.75 ± 1.60 years; height = 167.91 ± 8.96 cm; body mass = 69.00 ± 15.35 kg), 11 copers (2 male, 9 female; age = 22.81 ± 5.65 years; height = 166.09 ± 7.41 cm; body mass = 66.89 ± 9.60 kg), and 15 healthy controls (4 male, 11 female; age = 20.73 ± 1.62 years; height = 166.78 ± 9.39 cm; 65.91 ± 9.66 kg) volunteered.
Intervention Single-pulse transcranial magnetic stimulation was used to measure corticospinal excitatory and inhibitory pathways in seated and single-leg balance positions.
Main outcome measurements Active motor threshold (AMT) and corticospinal silent period (CSP) at 120% of AMT were assessed. Separate one-way ANOVAs were used to compare each dependent variable between groups for both conditions. Tukeys post hoc analyses were performed as needed. Significance was set a priori at p < 0.05.
Results There were no statistically significant group differences in AMT or CSP during the seated position (AMT: F28,2 = 1.36, p = 0.87; CSP: F27,2 = 0.294, p = 0.75) or the standing position (AMT: F28,2 = 0.603, p = 0.55; CSP: F28,2 = 1.35, p = 0.28).
Conclusions Corticospinal alterations in the tibialis anterior muscle were not observed in CAI participants during seated or standing positions. The testing position of corticospinal excitability and inhibitory mechanisms should be explored in other stabilising muscles (soleus, fibularis longus) that have shown greater influence from CAI.
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