Chronic ankle instability (CAI) is associated with centralized feed-forward neuromuscular alterations that affect the hip as well as the ankle, according to research from Boston University that may have implications for rehabilitation programs in that patient population.
“Because we do see that those with CAI demonstrate changes in muscle activation and neuromuscular control throughout the lower extremity, including at the hip, clinicians should evaluate the hip musculature in patients with CAI to enhance rehabilitation protocols and ensure the entire lower extremity chain is involved in the rehabilitation process,” said lead author Kathryn Webster, PhD, ATC, a clinical assistant professor in the physical therapy and athletic training department at Boston University.
The cross-sectional study included 16 physically active individuals with CAI (eight women), with an average age of around 20 years, and 16 control participants without CAI who were matched for age, height, body mass, and sex. Investigators measured electromyographic (EMG) activation of the tibialis anterior, peroneus longus, gluteus medius, and gluteus maximus muscles 200 ms before and after the participants landed from a lateral hop.
EMG was assessed before and after a fatigue protocol, which included cone drills (involving combinations of forward sprints, lateral shufﬂes, pivoting, and backward running), repeated two-footed lateral hops, and a drill that involved stepping up and hopping down from boxes of different heights.
Just before landing a lateral hop, activation values in the peroneus longus and gluteus maximus muscles were higher in participants with CAI than in the control group. Between-group differences were also evident for prelanding activation in the same muscles following the fatigue protocol.
The tibialis anterior was the only muscle for which postfatigue activation was significantly higher than prefatigue activation; this was true across both groups, for both the prelanding and postlanding measurements.
The findings were epublished by the Journal of Athletic Training in September.
The increased muscle activation prior to landing in participants with CAI supports the concept of a centralized feed-forward neural adaptation—involving both proximal and distal muscles—to a compromised ability to protect the ankle, the authors suggested in the paper.
“Because the effects of CAI are seen throughout activities of daily living, rehabilitation involving restoration of proper neuromuscular control is important to attempt to prevent subsequent injury,” Webster said.
Individuals with CAI also demonstrated greater proximal muscle activation than controls in a study published in the April issue of Knee Surgery, Sports Traumatology, Arthroscopy. In that study, CAI was associated with increased surface EMG activation of the gluteus medius muscle during the late stance and early swing phases of walking.
“If someone has decreased hip strength following an ankle injury, a clinician should consider implementing hip exercises to target that specific deficit,” said first author Rachel Koldenhoven, MEd, ATC, a doctoral student in the Department of Kinesiology and Sports Medicine at the University of Virginia in Charlottesville.
The fatigue protocol used in the Boston University study may not have been sufficient to produce fatigue effects in the proximal muscles, which are larger than the distal muscles and may take longer to fatigue, Webster said. But the fact that the between-group differences for gluteus maximus activation were maintained after fatigue suggests it may be important for rehab programs to address both proximal and distal muscle function during a fatigued state.
“Neuromuscular control is negatively impacted with fatigue, and because this control is so closely tied to ankle instability, it seems reasonable to include stability exercises in rehab close to the end of a session, when a patient may be more fatigued,” Webster said.
Webster KA, Tome J, Pietrosimone BG, Gribble PA. Muscle activation during landing before and after fatigue in individuals with or without chronic ankle instability. J Athl Train 2016 Sep 14. [Epub ahead of print]
Koldenhoven RM, Feger MA, Fraser JJ, et al. Surface electromyography and plantar pressure during walking in young adults with chronic ankle instability. Knee Surg Sports Traumatol Arthrosc 2016;24(4):1060-1070.