Understanding the effects of a sudden directional shift in somatosensory feedback and increasing task complexity on postural adaptation in individuals with and without chronic ankle instability.

BACKGROUND: Individuals with chronic ankle instability (CAI) present somatosensory dysfunction following an initial ankle sprain. However, little is known about how individuals with CAI adapt to a sudden sensory perturbation of instability with increasing task and environmental constraints to maintain postural stability. METHODS: Forty-four individuals with and without unilateral CAI performed the Adaptation Test to a sudden somatosensory inversion and plantarflexion perturbations (environment) in double-, injured-, and uninjured- limbs. Mean sway energy scores were analyzed using 2 (group) × 2 (somatosensory perturbations) × 3 (task) repeated measures analysis of variance. RESULTS: There were significant interactions between the group, environment, and task (P=.025). The CAI group adapted faster than healthy controls to a sudden somatosensory inversion perturbation in the uninjured- (P=.002) and injured- (P<.001) limbs, as well as a sudden somatosensory plantarflexion perturbation in the double- (P=.033) and uninjured- (P=.035) limbs. The CAI and healthy groups presented slower postural adaptation to a sudden inversion perturbation than a sudden somatosensory plantarflexion perturbation in double-limb (P<.001). Whereas both groups demonstrated faster postural adaptation to a sudden somatosensory inversion perturbation compared to somatosensory plantarflexion perturbation while maintaining posture in the injured- (P<.001) and uninjured- (P<.001) limbs. The CAI and healthy groups adapted faster to a sudden somatosensory inversion perturbation in the injured- (P<.001) and uninjured- (P<.001) limbs than in double-limb, respectively. DISCUSSION: Postural adaptation in individuals with and without CAI depended on environmental (somatosensory perturbations) and task constraints. The CAI group displayed comparable and faster postural adaptation to a sudden somatosensory inversion and plantarflexion in double-, injured-, and uninjured- limbs, which may reflect a centrally mediated alteration in neuromuscular control in CAI.

Sensory Reweighting System Differences on Vestibular Feedback with Increased Task Constraints in Individuals with Chronic Ankle Instability Compared to Healthy Controls.

CONTEXT: Chronic ankle instability (CAI) is associated with a less flexibly adaptable sensorimotor system. Thus, individuals with CAI may present an inadequate sensory reweighting system inhibiting the ability to emphasize weight on reliable sensory feedback to control posture. However, how individuals with CAI reweight sensory feedback to maintain postural control in bilateral and unilateral stances has yet to be established. OBJECTIVES: The primary purpose was to examine group differences in how the sensory reweighting system changes to control posture in a simple double-limb stance and a more complex single-limb stance (uninjured-limb, injured-limb) under increased environmental constraints manipulating somatosensory and visual information for individuals with and without CAI. The secondary purpose was to examine the effect of environmental and task constraints on postural control. STUDY DESIGN: Case-control study. SETTING: Laboratory. PATIENTS OR OTHER PARTICIPANTS: 21 individuals with CAI (26.4±5.7years, 171.2±9.8cm, 76.6±15.17kg) and 21 healthy controls (25.8±5.7years, 169.5±9.5cm, 72.4±15.0kg) participated in the study. MAIN OUTCOME MEASURE(S): Equilibrium10 were examined while completing 6 environmental conditions of the Sensory Organization Test (SOT) during 3 tasks (double-limb and single-limb [uninjured, injured] stances). Sensory reweighting ratios for sensory systems (somatosensory, vision, vestibular) were computed from paired Equilibrium10. RESULTS: Significant 3-factor interactions were found between group, sensory systems, and tasks (P=0.006) and for groups, task, and environment (P=0.007). The CAI group failed to downweight vestibular feedback compared to healthy controls while maintaining posture in the injured-limb (P=0.030). The CAI group displayed better postural stability than healthy controls while standing with absent vision, fixed surroundings, and a moving platform in the injured-limb (P=0.032). CONCLUSIONS: The CAI group relied on vestibular feedback while maintaining better postural stability than healthy controls in the injured-limb. Group differences in postural control depended on both environmental (absent vision, moving platform) and task (injured-limb) constraints.

Effects of a Single Electrical Stimulation Session on Foot Force Production, Foot Dome Stability, and Dynamic Postural Control.

CONTEXT: Mounting evidence suggests neuromuscular electrical stimulation (NMES) as a promising modality for enhancing lower limb muscle strength, yet the functional effects of a single electrical stimulation session for improving the function of the intrinsic foot muscles (IFM) has not been evaluated. OBJECTIVE: To investigate the immediate effects of an NMES session compared with a sham stimulation session on foot force production, foot dome stability, and dynamic postural control in participants with static foot pronation. DESIGN: Randomized controlled clinical trial. SETTING: Laboratory. PATIENTS OR OTHER PARTICIPANTS: A total of 46 participants (23 males, 23 females) with static foot pronation according to their Foot Posture Index (score ≥ 6) were randomly assigned to an NMES (n = 23) or control (n = 23) group. INTERVENTION(S): The NMES group received a single 15-minute NMES session on the dominant foot across the IFM. The control group received a 15-minute sham electrical stimulation session. MAIN OUTCOME MEASURE(S): All outcome measurements were assessed before and after the intervention and consisted of foot force production on a pressure platform, foot dome stability, and dynamic postural control. Statistical analysis was based on the responsiveness of the outcome measures and responder analysis using the minimum detectable change scores for each outcome measure. RESULTS: In the NMES group, 78% of participants were classified as responders for at least 2 of the 3 outcomes, compared with only 22% in the control group. The relative risk of being a responder in the NMES group compared with the control group was 3.6 (95% CI = 1.6, 8.1]. Interestingly, we found that all participants who concomitantly responded to foot strength and navicular drop (n = 8) were also responders in dynamic postural control. CONCLUSIONS: Compared with a sham stimulation session, a single NMES session was effective in immediately improving foot function and dynamic postural control in participants with static foot pronation. These findings support the role of NMES for improving IFM function in this population.

Establishing Normative Dynamic Postural Control Values in Elite Female Handball Players.

Background: Lower extremity injuries among young female handball players are very common. The modified Star Excursion Balance Test (mSEBT) is a valid clinical tool to assess dynamic postural control and identify athletes with higher risk of injury. However, its interpretation is difficult since performance on this test is highly sport dependent. No normative values on the mSEBT exist in handball. Purpose: The aim of this investigation was to establish normative ranges of mSEBT performance in young, healthy female handball players to help practitioners when interpreting risk estimates. Study design: Cross-Sectional Study. Methods: Athletes from 14 elite teams were recruited during a national tournament and performed 3 trials in the anterior (ANT), posteromedial (PM), posterolateral (PL) directions of the mSEBT. Means, standard deviations and 95% confidence intervals (95%CI) of normalized reached distances were calculated for each direction and the composite score (COMP). Level of asymmetry between dominant and non-dominant limbs were calculated for each direction using Bland Altman analyses. Group differences were weighed against the established mSEBT minimum detectable differences (MDD) to compare scores between limbs and across different player positions. Results: One-hundred and eighty-eight females (16.8±0.9 years) were tested. Mean reach distances were 65.2±5% (64.7-65.7), 110.0±6.2% (109.3-110.6), 107.1±6.2% (106.5-107.8) and 94.1±4.9% (93.6-94.6) for the ANT, PM, PL directions and COMP score respectively. Bias and limits of agreement for limb asymmetry were -0.23% (-5.85%, 5.38%) for ANT, -0.83% (-8.80%, 7.14%) for PM, 0.33% (-8.51%, 9.17%) for PL and -0.27% (-4.88%, 4.33%) for COMP score. No meaningful differences were observed between limbs or across player positions since the values did not exceed the MDD and all 95%CIs overlapped. Conclusion: This study provides normative performance values for dynamic postural control as measured by the mSEBT among young, healthy, elite female handball players. Considering the high incidence of injury in this population, these values can be used for injury risk reduction and return to sport decisions. Further prospective studies are needed to established specific cut-off scores in this population. Level of evidence: 2c.

Use of time-to-boundary to assess postural instability and predict functional mobility in people with diabetes mellitus and peripheral neuropathy.

BACKGROUND: People with diabetes mellitus and peripheral neuropathy (DMPN) often have balance and mobility deficits. Time-to-boundary (TTB) is a parameter of postural control that combines position and velocity center of pressure data. While not previously investigated, assessment of TTB may provide new insight regarding postural control in people with DMPN. RESEARCH QUESTION: Is TTB reduced and related to a measure of mobility in people with DMPN? METHODS: Thirteen people with DMPN without fall history and 13 healthy matched controls participated in this case-control study. Participants stood in double-limb stance on a force plate. The anterior-posterior and medial-lateral center of pressure position and velocity relative to the boundaries of the base of support were used to calculate TTB (s). Lower values indicate less postural control. Time-to-failure during single-limb stance was a secondary measure of postural control. Time to complete the Timed Up and Go (TUG) was our measure of mobility. Longer TUG times correspond to decreased mobility, strength, and balance. Independent t-tests or Mann-Whitney U tests were conducted to assess group differences. Bivariate correlations between task outcomes were conducted. RESULTS: Anterior-posterior TTB and single-limb stance times were shorter in people with DMPN (p ≤  0.04). TUG times were longer in the DMPN group (p =  0.04). In the DMPN group, inverse relationships were observed between TTB and TUG (anterior-posterior R2 = .34; medial-lateral R2 = .49; both p =  0.01), but not between single-limb stance times and TTB or TUG. SIGNIFICANCE: TTB was a sensitive measure of postural control in people with DMPN. The detected relationship between TTB and TUG newly establishes TTB as a clinically meaningful indicator of balance and function. Study findings may serve to further guide balance screening and rehabilitation efforts in people with DMPN.

Efficacy of Kinesio Taping and McConnell Taping Techniques in the Management of Anterior Knee Pain.

CONTEXT: Anterior knee pain also known as patellofemoral pain syndrome is a frequently encountered musculoskeletal disorder that worsens with activity. The multifactorial etiology of patellofemoral pain syndrome alters lower-extremity mechanics, increasing patellofemoral joint stresses during weight-bearing tasks. Kinesio and McConnell tapings are often incorporated into the treatment, but their efficacy is still unclear. OBJECTIVE: To test the efficacy of Kinesio taping, McConnell taping, and sham taping in improving knee mechanics and reducing pain during activity. DESIGN: Cross-sectional design. SETTING: Clinical biomechanics laboratory. PARTICIPANTS: Ten participants (age: 20.3 [1.5] y, height: 169.9 [10.4] cm, and mass: 70.17 [13.1] kg) with anterior knee pain and no history of trauma. INTERVENTION: Three trials each of squat, drop jump, and step-down tasks with 3 taping conditions in a counterbalanced order. MAIN OUTCOME MEASURES: Two-dimensional motion capture data of lower-extremities in frontal and sagittal planes were recorded and analyzed using 3 iPads and Spark Motion® application. Pooled effect sizes (Hedges' g), 95% confidence intervals, and repeated-measures analysis of variance (P < .05) compared baseline and taping conditions during exercises for pain Visual Analog Scale and knee flexion in all exercises, hip abduction during step-down and drop jump, frontal plane projection during step-downs, and knee translation in sagittal plane during squats. RESULTS: Significant reductions in Visual Analog Scale were recorded during squats between tapes (F2.505,12.867 = 3.407, P = .04, Hedges' g = -0.70). Pairwise comparison showed a decrease in Visual Analog Scale for sham taping (mean difference = 1.14 cm, P = .01) and Kinesio taping (mean difference = 1.54 cm, P = .02) compared with baseline during squats. CONCLUSIONS: A variety of taping methods can potentially reduce perceived pain in individuals with patellofemoral pain syndrome, allowing clinicians to perform rehabilitation exercises. Sensory effects associated with short-term taping may be sufficient enough to modify knee pain acutely by afferent input blocking nocioceptive pain before the participants could adapt. Most interestingly, the sham taping technique demonstrated promise for enhancing functional outcomes, depending on the length of the tape and area covered.

A Perceptual Framework for Conservative Treatment and Rehabilitation of Ankle Sprains: An Evidence-Based Paradigm Shift.

Lateral ankle sprains are the most common injuries sustained during physical activity. The epidemiologic trends associated with chronic ankle instability (CAI) suggest that current rehabilitation approaches may be inadequate. We sought to synthesize best-practices evidence for the rehabilitation of patients with acute ankle sprains and CAI through the integration of emerging paradigms in perception, the dynamics of skill acquisition, and the biopsychosocial model of function, disability, and health. From the best available evidence, 4 key factors emerged for effective treatment and rehabilitation strategies: pain reduction, external ankle support for up to 1 year, progressive return to motion, and coordination training. We combined these factors into a meta-theoretical framework that centers on the perceptual interdependence of the cellular, local, and global functioning levels by linking insights from the body-self neuromatrix, the dynamics of skill acquisition, and the biopsychosocial model. Based on the best-practice recommendations from systematic reviews, ankle-sprain rehabilitation represents a multidimensional phenomenon governed by perception. The impairments, activity limitations, and participation restrictions associated with CAI may be linked to perceptual-interdependence alterations. Pain and edema reduction, the use of external ankle support for up to 1 year, progressive return to motion, and coordination training foster enhanced perceptual interdependence from cells to society. Using the perceptual-interdependence framework for ankle-sprain rehabilitation, we offer new insights for charting the course of effective strategies for enhancing function, reducing disability, and preventing the long-term sequelae associated with CAI.

Predicting dynamic balance improvements following 4-weeks of balance training in chronic ankle instability patients.

OBJECTIVES: Balance training typically features as a central component of exercise-based rehabilitation programs for patients with lateral ankle sprain and chronic ankle instability (CAI). The purpose of this study was to conduct a responder/non-responder analysis using existing data to identify factors associated with improvements in dynamic balance performance in CAI patients. DESIGN: Secondary data analysis. METHODS: Data was used from 73 CAI patients who participated in 6 previous investigations that used the same balance training program. We defined treatment success as a patient exceeding the minimal detectable change score (8.15%) for the posteriomedial direction of the Star Excursion Balance Test (SEBT-PM). Baseline measures of participant and injury demographics, patient-reported function, and dynamic balance were entered into a step-wise logistic regression model to determine the best set of predictors of treatment success. RESULTS: Only 28 out of 73 patients (38.4%) demonstrated a successful improvement in SEBT-PM reach after balance training. Of the variables assessed, SEBT-PM reach distance ≤85.18% and self-reported function activities of daily living score ≤92.55% were significant predictors of treatment success (p<0.001). If a patient met both these criteria there was a 70% probability of a successful treatment, indicating a 31.6% increase in the probability of a meaningful balance improvement after completing balance training. CONCLUSIONS: Without screening, less than 40% of CAI patients experience a meaningful improvement in SEBT-PM following balance training. Completing a brief pre-treatment assessment of a patient- and clinician-oriented outcome can significantly improve the probability of determining patients with CAI who may improve dynamic balance after balance training.

The effect of sensory-targeted ankle rehabilitation strategies on single-leg center of pressure elements in those with chronic ankle instability: A randomized clinical trial.

OBJECTIVES: To determine the effects of sensory-targeted ankle rehabilitation strategies on laboratory-oriented measures of single-leg balance in those with chronic ankle instability. DESIGN: Non-inferiority randomized controlled trial. METHODS: Seventy-seven participants with self-reported chronic ankle instability were randomized into 4 treatment groups: Ankle joint mobilization, plantar massage, triceps surae stretching, and a control group. All participants performed 3 trials of single-leg balance on a force plate with eyes open and closed at 3 time points (baseline, immediately after the first treatment, and following 6 treatments over 2 weeks). The spatial (standard deviation), temporal (velocity), and spatiotemporal (time-to-boundary) elements of center of pressure excursions in single-leg balance were evaluated with eyes open and eyes closed at each time point. Immediate and final change scores were calculated for each group from the baseline values on these variables. RESULTS: Joint mobilization produced immediate improvements in the temporal elements with eyes open and closed that exceeded the minimum detectable changes for these measures. Plantar massage and triceps surae stretching also enhanced the temporal element after a single treatment, but only with eyes closed. No substantial benefit of any of the interventions were found after 2-weeks of treatment, regardless of treatment group. CONCLUSIONS: Sensory-targeted ankle rehabilitation strategies substantially improve single-leg postural control after one treatment, but these changes are short-lived. Future research is needed to determine whether combinations of sensory-targeted ankle rehabilitation strategies with other therapeutic interventions potentially improve single-leg balance stability in those with CAI compared to use in isolation. CLINICAL TRIAL REGISTRATION NUMBER: NCT01541657.

Visual perturbation impacts upright postural stability in athletes with an acute concussion.

OBJECTIVE: The impact that visual perturbation has on upright postural stability in an athlete with a concussion has not been established. The present study aimed to characterize the influence that visual perturbation stimuli have on upright balance among athletes with acute concussions. DESIGN: A 2X2X2 repeated measure designed was used. METHOD: The present study examined the influence visual perturbation has on individuals suffering from an acute concussion. Fourteen participants (7 with a concussion and 7 matched controls) underwent various balance assessments with and without visual perturbation. RESULTS: Overall, athletes with acute concussions demonstrated impairments in balance 24-48 hours following a concussion. However, when assessed using a visual perturbation task, athletes with acute concussions demonstrated improved balance, while control subjects did not show any significant changes during the same visual perturbation task. CONCLUSION: An athlete's ability to disregard visual perturbation stimuli is imperative for successful participation in sports. Due to the observed alterations in balance when given a visual perturbation task, it is suggested that athletes with acute concussions place more attention on the balance task and may disregard other less meaningful tasks.

Clinical assessment of acute lateral ankle sprain injuries (ROAST): 2019 consensus statement and recommendations of the International Ankle Consortium.

Lateral ankle sprain injury is the most common musculoskeletal injury incurred by individuals who participate in sports and recreational physical activities. Following initial injury, a high proportion of individuals develop long-term injury-associated symptoms and chronic ankle instability. The development of chronic ankle instability is consequent on the interaction of mechanical and sensorimotor insufficiencies/impairments that manifest following acute lateral ankle sprain injury. To reduce the propensity for developing chronic ankle instability, clinical assessments should evaluate whether patients in the acute phase following lateral ankle sprain injury exhibit any mechanical and/or sensorimotor impairments. This modified Delphi study was undertaken under the auspices of the executive committee of the International Ankle Consortium. The primary aim was to develop recommendations, based on expert (n=14) consensus, for structured clinical assessment of acute lateral ankle sprain injuries. After two modified Delphi rounds, consensus was achieved on the clinical assessment of acute lateral ankle sprain injuries. Consensus was reached on a minimum standard clinical diagnostic assessment. Key components of this clinical diagnostic assessment include: establishing the mechanism of injury, as well as the assessment of ankle joint bones and ligaments. Through consensus, the expert panel also developed the International Ankle Consortium Rehabilitation-Oriented ASsessmenT (ROAST). The International Ankle Consortium ROAST will help clinicians identify mechanical and/or sensorimotor impairments that are associated with chronic ankle instability. This consensus statement from the International Ankle Consortium aims to be a key resource for clinicians who regularly assess individuals with acute lateral ankle sprain injuries.

Effects of ageing on orofacial fine force control and its relationship with parallel change in sensory perception.

PURPOSE: Current theoretical models suggest the importance of a bidirectional relationship between sensation and production in the vocal tract to maintain lifelong speech skills. The purpose of this study was to assess age-related changes in orofacial skilled force production and to begin defining the orofacial perception-action relationship in healthy adults. METHOD: Low-level orofacial force control measures (reaction time, rise time, peak force, mean hold force (N) and force hold SD) were collected from 60 adults (19-84 years). Non-parametric Kruskal Wallis tests were performed to identify statistical differences between force and group demographics. Non-parametric Spearman's rank correlations were completed to compare force measures against previously published sensory data from the same cohort of participants. RESULT: Significant group differences in force control were found for age, sex, speech usage and smoking status. Significant correlational relationships were identified between labial vibrotactile thresholds and several low-level force control measures collected during step and ramp-and-hold conditions. CONCLUSION: These findings demonstrate age-related alterations in orofacial force production. Furthermore, correlational analysis suggests as vibrotactile detection thresholds increase, the ability to maintain low-level force control accuracy decreases. Possible clinical applications and treatment consequences of these findings for speech disorders in the ageing population are provided.

Predicting Manual Therapy Treatment Success in Patients With Chronic Ankle Instability: Improving Self-Reported Function.

CONTEXT: Therapeutic modalities that stimulate sensory receptors around the foot-ankle complex improve chronic ankle instability (CAI)-associated impairments. However, not all patients have equal responses to these modalities. Identifying predictors of treatment success could improve clinician efficiency when treating patients with CAI. OBJECTIVE: To conduct a response analysis on existing data to identify predictors of improved self-reported function in patients with CAI. DESIGN: Secondary analysis of a randomized controlled clinical trial. SETTING: Sports medicine research laboratories. PATIENTS OR OTHER PARTICIPANTS: Fifty-nine patients with CAI, which was defined in accordance with the International Ankle Consortium recommendations. INTERVENTION(S): Participants were randomized into 3 treatment groups (plantar massage [PM], ankle-joint mobilization [AJM], or calf stretching [CS]) that received six 5-minute treatments over 2 weeks. MAIN OUTCOME MEASURE(S): Treatment success, defined as a patient exceeding the minimally clinically important difference of the Foot and Ankle Ability Measure-Sport (FAAM-S). RESULTS: Patients with ≤5 recurrent sprains and ≤82.73% on the Foot and Ankle Ability Measure had a 98% probability of having a meaningful FAAM-S improvement after AJM. As well, ≥5 balance errors demonstrated 98% probability of meaningful FAAM-S improvements from AJM. Patients <22 years old and with ≤9.9 cm of dorsiflexion had a 99% probability of a meaningful FAAM-S improvement after PM. Also, those who made ≥2 single-limb-stance errors had a 98% probability of a meaningful FAAM-S improvement from PM. Patients with ≤53.1% on the FAAM-S had an 83% probability of a meaningful FAAM-S improvement after CS. CONCLUSIONS: Each sensory-targeted ankle-rehabilitation strategy resulted in a unique combination of predictors of success for patients with CAI. Specific indicators of success with AJM were deficits in self-reported function, single-limb balance, and <5 previous sprains. Age, weight-bearing-dorsiflexion restrictions, and single-limb balance deficits identified patients with CAI who will respond well to PM. Assessing self-reported sport-related function can identify CAI patients who will respond positively to CS.

Predicting balance improvements following STARS treatments in chronic ankle instability participants.

OBJECTIVES: Sensory Targeted Ankle Rehabilitation Strategies that stimulate sensory receptors improve postural control in chronic ankle instability participants. However, not all participants have equal responses. Therefore, identifying predictors of treatment success is needed to improve clinician efficiency when treating chronic ankle instability. Therefore, the purpose was to identify predictors of successfully improving postural control in chronic ankle instability participants. DESIGN: Secondary data analysis. METHODS: Fifty-nine participants with self-reported chronic ankle instability participated. The condition was defined as a history of at least two episodes of "giving way" within the past 6 months; and limitations in self-reported function as measured by the Foot and Ankle Ability Measure. Participants were randomized into three treatment groups (plantar massage, ankle joint mobilization, calf stretching) that received 6, 5-min treatment sessions over a 2-week period. The main outcome measure was treatment success, defined as a participant exceeding the minimal detectable change score for a clinician-oriented single limb balance test. RESULTS: Participants with ≥3 balance test errors had a 73% probability of treatment success following ankle joint mobilizations. Participants with a self-reported function between limb difference <16.07% and who made >2.5 errors had a 99% probability of treatment success following plantar massage. Those who sustained ≥11 ankle sprains had a 94% treatment success probability following calf stretching. CONCLUSIONS: Self-reported functional deficits, worse single limb balance, and number of previous ankle sprains are important characteristics when determining if chronic ankle instability participants will have an increased probability of treatment success.

Neuromuscular Alterations After Ankle Sprains: An Animal Model to Establish Causal Links After Injury.

CONTEXT: The mechanisms that contribute to the development of chronic ankle instability are not understood. Investigators have developed a hypothetical model in which neuromuscular alterations that stem from damaged ankle ligaments are thought to affect periarticular and proximal muscle activity. However, the retrospective nature of these studies does not allow a causal link to be established. OBJECTIVE: To assess temporal alterations in the activity of 2 periarticular muscles of the rat ankle and 2 proximal muscles of the rat hind limb after an ankle sprain. DESIGN: Controlled laboratory study. SETTING: Laboratory. PATIENTS OR OTHER PARTICIPANTS: Five healthy adult male Long Evans rats (age = 16 weeks, mass = 400.0 ± 13.5 g). INTERVENTION(S): Indwelling fine-wire electromyography (EMG) electrodes were implanted surgically into the biceps femoris, medial gastrocnemius, vastus lateralis, and tibialis anterior muscles of the rats. We recorded baseline EMG measurements while the rats walked on a motor-driven treadmill and then induced a closed lateral ankle sprain by overextending the lateral ankle ligaments. After ankle sprain, the rats were placed on the treadmill every 24 hours for 7 days, and we recorded postsprain EMG data. MAIN OUTCOME MEASURE(S): Onset time of muscle activity, phase duration, sample entropy, and minimal detectable change (MDC) were assessed and compared with baseline using 2-tailed dependent t tests. RESULTS: Compared with baseline, delayed onset time of muscle activity was exhibited in the biceps femoris (baseline = -16.7 ± 54.0 milliseconds [ms]) on day 0 (5.2 ± 64.1 ms; t4 = -4.655, P = .043) and tibialis anterior (baseline = 307.0 ± 64.2 ms) muscles on day 3 (362.5 ± 55.9 ms; t4 = -5.427, P = .03) and day 6 (357.3 ± 39.6 ms; t4 = -3.802, P = .02). Longer phase durations were observed for the vastus lateralis (baseline = 321.9 ± 92.6 ms) on day 3 (401.3 ± 101.2 ms; t3 = -4.001, P = .03), day 4 (404.1 ± 93.0 ms; t3 = -3.320, P = .048), and day 5 (364.6 ± 105.2 ms; t3 = -3.963, P = .03) and for the tibialis anterior (baseline = 103.9 ± 16.4 ms) on day 4 (154.9 ± 7.8 ms; t3 = -4.331, P = .050) and day 6 (141.9 ± 16.2 ms; t3 = -3.441, P = .03). After sprain, greater sample entropy was found for the vastus lateralis (baseline = 0.7 ± 0.3) on day 6 (0.9 ± 0.4; t4 = -3.481, P = .03) and day 7 (0.9 ± 0.3; t4 = -2.637, P = .050) and for the tibialis anterior (baseline = 0.6 ± 0.4) on day 4 (0.9 ± 0.5; t4 = -3.224, P = .03). The MDC analysis revealed increased sample entropy values for the vastus lateralis and tibialis anterior. CONCLUSIONS: Manually inducing an ankle sprain in a rat by overextending the lateral ankle ligaments altered the complexity of muscle-activation patterns, and the alterations exceeded the MDC of the baseline data.