Alterations in evertor/invertor muscle activation and center of pressure trajectory in participants with functional ankle instability

Context: Ankle sprains are among the most common musculoskeletal injuries, and many individuals with ankle sprains develop chronic ankle instability (CAI). Individuals with CAI exhibit proprioceptive and postural-control deficits, as well as altered osteokinematics, during gait. Neuromuscular activity is theorized to play a pivotal role in CAI, but deficits during walking are unclear.Objective: To compare motor-recruitment patterns as demonstrated by surface electromyography amplitudes between participants with CAI and healthy control participants during walking.Design: Descriptive laboratory study. Setting: Laboratory.Patients or Other Participants: Fifteen adults with CAI (5 men, 10 women; age ¼ 23 6 4.2 years, height ¼ 173 6 10.8 cm, mass ¼ 72.4 6 14 kg) and 15 matched healthy control adults (5 men, 10 women; age ¼ 22.9 6 3.4 years, height ¼ 173 6 9.4 cm, mass ¼ 70.8 6 18 kg).Intervention(s): Participants walked shod on a treadmill while surface electromyography signals were recorded from the anterior tibialis, peroneus longus, lateral gastrocnemius, rectus femoris, biceps femoris, and gluteus medius muscles.Main Outcome Measure(s): Preinitial contact amplitude, postinitial contact amplitude, time of activation relative to initial contact, and percentage of activation time across the stride cycle were calculated for each muscle.Results: Time of activation for all muscles tested occurred earlier in the CAI group than in the control group. The peroneus longus was activated for a longer duration across the entire stride cycle in the CAI group (36.0% 6 10.3%) than the control group (23.3% 6 22.2%; P ¼ .05). No differences were noted between groups for measures of electromyographic amplitude at either preinitial or postinitial contact (P . .05).Conclusions: We identified differences between the CAI and control groups in the timing of muscle activation relative to heel strike in multiple lower extremity muscles and in the percentage of activation time across the entire stride cycle in the peroneus longus muscle. Individuals with CAI demonstrated neuromuscular-activation strategies throughout the lower extremity that were different from those of healthy control participants. Targeted therapeutic interventions for CAI may need to be focused on restoring normal neuromuscular function during gait.

Section: Discussionmentioning

confidence: 91%

Section: Discussionmentioning

confidence: 99%

Lower Extremity Muscle Activation in Patients With or Without Chronic Ankle Instability During Walking

Feger

Donovan

Hart

et al. 2015

“…In addition to ankle dorsiflexion, researchers 40,41 have shown that both the TA and PL have coupled activity during inversion and eversion of the ankle, which helps the ankle remain in a neutral position and maintains balance during the stance phase of gait. With our experimental task, this coupled activity was likely used to maintain mediolateral ankle and body stability, especially after the kick (CPA2).…”

Section: Discussionmentioning

confidence: 99%

Changes in Postural Control After a Ball-Kicking Balance Exercise in Individuals With Chronic Ankle Instability

Conceição

Araújo

Santos

et al. 2016

Context:Rehabilitation programs for patients with chronic ankle instability (CAI) generally involve balance-perturbation training (BPT). Anticipatory postural adjustments (APAs) and compensatory postural adjustments (CPAs) are the primary strategies used to maintain equilibrium during body perturbations. Little is known, however, about how APAs and CPAs are modified to promote better postural control for individuals with CAI after BPT.Objective: To investigate the effect of BPT that involves kicking a ball on postural-control strategies in individuals with CAI.Design: Randomized controlled clinical trial. Setting: Laboratory. Patients or Other Participants: We randomly assigned 44 volunteers with CAI to either a training group (TG; 11 women, 11 men; age ¼ 24 6 4 years, height ¼ 173.0 6 9.8 cm, mass ¼ 72.64 6 11.98 kg) or control group (CG; 11 women, 11 men; age ¼ 22 6 3 years, height ¼ 171.0 6 9.7 cm, mass ¼ 70.00 6 11.03 kg).Intervention(s): The TG performed a single 30-minute training session that involved kicking a ball while standing on 1 foot. The CG received no intervention.Main Outcome Measure(s): The primary outcome was the sum of the integrated electromyographic activity ( PR EMG) of the lower extremity muscles in the supporting limb that were calculated during typical intervals for APAs and CPAs. A secondary outcome was center-of-pressure displacement during similar intervals.Results: In the TG after training, the PR EMG decreased in both dorsal and ventral muscles during compensatory adjustment (ie, the time interval that followed lower limb movement). During this interval, muscle activity ( PR EMG) was less in the TG than in the CG. Consequently, center-of-pressure displacement increased during the task after training.Conclusions: A single session of ball-kicking BPT promoted changes in postural-control strategies in individuals with CAI. These results should stimulate new and more comprehensive studies to investigate the effect of this and other BPT techniques on postural control in patients with CAI.Key Words: recurrent sprains, reactive responses, balance training Key PointsAfter balance-perturbation training, postural sway increased during the ball-kicking activity and decreased during a static task in individuals with chronic ankle instability. Ventral and dorsal muscle activity decreased just before kicking the ball, and tibialis anterior and peroneus longus activity increased after the kick in the balance-perturbation-training group. Researchers should conduct more comprehensive studies to determine if balance-perturbation training improves postural control and simultaneously augments ankle stability in individuals with chronic ankle instability.

“…Through various portions of the gait cycle, people with CAI walk and run with altered ankle and foot kinematics compared with uninjured people. 4 In walking, kinetic differences include greater peak plantar pressure in the midfoot and lateral forefoot, 5 a laterally deviated center of pressure (COP), 6 and increased braking and propulsive forces 7 compared with uninjured participants. While running, individuals with CAI have increased pressure within the lateral rear foot and a lateral COP trajectory compared with a medial COP trajectory in healthy individuals during the loading response phase.…”

mentioning

confidence: 99%

Altered Vertical Ground Reaction Forces in Participants With Chronic Ankle Instability While Running

Bigouette

Simon

Liu

et al. 2016

Context: Altered gait kinetics may increase the risk of longterm injuries in participants with chronic ankle instability (CAI). Vertical ground reaction forces (vGRFs) can provide insight into how body loading is altered.Objective: To compare the components of vGRFs while running in participants with or without CAI.Design: Cohort study. Setting: University biomechanics laboratory.Patients or Other Participants: Twenty-four experienced, college-aged runners. Groups were categorized by the presence (CAI group) or absence (control group) of CAI through selfreported questionnaires.Intervention(s): After a warm-up period, all participants ran on an instrumented treadmill for 5 minutes at 3.3 m/s. Data were collected during the last 30 seconds. Five continuous trials of heel-to-toe running were identified per participant and averaged for statistical analysis.Main Outcome Measure(s): The dependent variables were impact peak force (N/body weight [BW]), active peak force (N/ BW), time to impact peak force (milliseconds), time to active peak force (milliseconds), and average loading rate ([N/BW]/s).Results: A difference was found between groups (P ¼ .002). The CAI group had higher impact peak forces (P ¼ .001) and active peak forces (P ¼ .002) compared with the control group. The CAI group also had an increased loading rate (P ¼ .001) and a shorter time to reach the active peak force (P ¼ .001) compared with the control group. No difference was seen between groups in the time to reach the impact peak force (P ¼ .952).Conclusions: Participants with CAI produced altered vGRFs and loading rates while running. Altered loading rates could predispose individuals with CAI to stress-related injuries and repetitive sprains.Key Words: biomechanics, gait, kinetics, stress fractures Key PointsThe group with chronic ankle instability demonstrated greater vertical ground reaction forces and initial and active peak forces. Those with chronic ankle instability also had increased loading rates, which could make them vulnerable to stress injuries and sprains.