Alterations in bilateral inter-joint coordination variability and intermuscular coherence in individuals with unilateral chronic ankle instability during landing: a cross-sectional study

Abstract

Chronic ankle instability (CAI) is a common musculoskeletal condition accompanying sensorimotor dysfunction. Recent research indicates that people with unilateral CAI not only present impairments on the injured side, but also exhibit deficits on the contralateral side. Studies have observed abnormal muscle activation and co-contractions in people with CAI, suggesting potential muscle coordination disorders. Considering the observed bilateral dysfunction, this study aimed to investigate characteristics of bilateral motor control and muscle coordination via intermuscular coherence (IMC) in people with unilateral CAI. Thirty participants with unilateral CAI and 30 healthy controls were recruited. Surface electromyography of muscle pairs in bilateral limbs was measured during single-leg stance and landing: rectus femoris-biceps femoris, tibialis anterior (TA)-peroneus longus (PL), TA-gastrocnemius medial, and TA-soleus (SOL). The sway velocity of center of pressure (COPV) was calculated for single-leg stance recorded by force plate, and joint coordination pattern and variability were analyzed for hip sagittal-ankle sagittal, hip sagittal-ankle frontal, knee sagittal-ankle sagittal, knee sagittal-ankle frontal (KSAF) and knee frontal-ankle frontal coupling pairs before and after landing. CAI group displayed postural instability (anteroposterior: mean difference (MD) = 3.87 mm/s, mediolateral: MD = 5.52 mm/s), higher KSAF variability (MD = 1.72˚), higher TA-PL β (MD = 0.035) and TA-SOL β (MD = 0.024) IMC bilaterally. An increased number of ankle sprains were correlated with higher IMC during post-landing bilaterally (injured: ꞵ = 0.398, adjusted R 2  = 0.129, uninjured: ꞵ = 0.387, adjusted R 2  = 0.120). Associations between IMC and COPV and coordination variability for both groups were observed ( p  ≤ 0.044). There were also correlations of IMC between two sides in unilateral CAI group ( p  ≤ 0.041), especially for the TA-SOL muscle pair. People with unilateral CAI displayed higher variability and IMC during landing bilaterally, suggesting abnormal motor regulation and additional central involvement. The number of ankle sprains and function on the injured side may modulate the function on the uninjured side. Rehabilitation or training for people with unilateral CAI may need to transition from injured side to bilateral sides or employ methods that could modulate bilateral functions.