EMG Analysis During Static Balance in Chronic Ankle Instability, Coper and Controls.

Patients with chronic ankle instability (CAI) consistently display postural control alterations, which may result from sensorimotor dysfunction. This study aimed to compare muscle activity in the lower extremity and postural control among individuals with CAI, copers and uninjured controls during a static balance test. A total of 57 physically active participants were categorized into three groups (CAI, copers and controls) and performed a single-leg balance test with two visual conditions: eyes open and eyes closed. Muscle activity in six lower extremity muscles and center of pressure (CoP) variables were recorded and analyzed. Patients with CAI exhibited greater muscle activity in the medial gastrocnemius and gluteus maximus compared to controls or copers, regardless of the visual condition. Copers displayed increased gluteus medius activity compared to controls. Additionally, all groups demonstrated increased muscle activity and CoP variables when visual feedback was disrupted. These findings suggest that patients with CAI may have less effective recruitment of motor units during static balance. On the other hand, greater muscle activity in the gluteus medius in copers may represent a coping mechanism to avoid further ankle injuries. Further research on muscle activity during dynamic postural control is warranted to explore sensorimotor alterations in patients with CAI.

Postural control measured before and after simulated ankle inversion landings among individuals with chronic ankle instability, copers, and controls.

BACKGROUND: Postural control measured during single-leg stance and single-leg hop stabilization has been used to estimate sensorimotor function in CAI individuals and copers. To date, studies have not used postural control tasks as a way of measuring responses to sudden changes in sensory information after simulated ankle inversion landings. RESEARCH QUESTION: A cross-sectional study was performed to identify any differences in static and dynamic postural control before and after simulated ankle inversion landings among individuals with chronic ankle instability (CAI), copers, and healthy controls. METHODS: Nineteen CAI individuals, 19 copers, and 19 controls participated in this study. Participants performed 3 static and dynamic balance tasks before and after simulated ankle inversion landings onto a 25° tilted platform from a height of 30 cm. The main outcome measures were the center of pressure (COP) velocity and range from the single-leg stance, as well as the dynamic postural stability index from the single-leg hop stabilization. The Wilcoxon signed-rank test was used to compare posttest and pretest differences in static and dynamic postural control between groups. RESULTS: In the static postural control measures, the CAI group had a higher difference in COP velocity and COP range in the frontal plane (p < 0.05 and p < 0.05, respectively) than the coper group. In the dynamic postural control measures, the CAI group demonstrated a higher difference in the vertical stability index (p < 0.05) than the healthy control group. SIGNIFICANCE: CAI individuals have persistent worse postural control after somatosensory modulation due to their inability to adapt to sudden somatosensory modulation. Relative to CAI individuals, copers may have different abilities not only the integration of somatosensory input about ankle inversion modulation, but also the adaptation of the entire motor control system, preventing recurrent ankle sprains after an initial LAS. Therefore, somatosensory modulation may be the indicator of understanding CAI and coper.

Visual Disruption Influences Neuromechanics during Landing Cutting in Individuals with Chronic Ankle Instability.

CONTEXT: Individuals with chronic ankle instability (CAI) appear to demonstrate altered movement patterns when their vision is disturbed during simple tasks such as single-leg standing and walking. However, it remains unclear whether visual disruption by stroboscopic glasses alters movement patterns during landing cutting movements, considered highly demanding sports maneuvers that mimic a typical athletic movement. OBJECTIVE: This study aimed to identify altered lower extremity kinematics and muscle activation when participants' vision was disrupted by stroboscopic glasses during landing cutting tasks in CAI patients. DESIGN: A case control design. SETTING: A controlled laboratory setting. PATIENTS OR OTHER PARTICIPANTS: Eighteen CAI patients and 18 matched healthy controls volunteered to participate in the study. All participants performed 5 trials of landing cutting with (SV) and without (NSV) stroboscopic glasses. MAIN OUTCOME MEASURES: Frontal and sagittal lower extremity kinematics, and 6 lower extremity muscle activations during the stance phase of landing cutting tasks with (SV) and without stroboscopic glasses (NSV). RESULTS: CAI patients demonstrated more inversion angle from 18% to 22% and from 60% to 100% of the stance phase and more peroneal longus activation from initial contact to 18% of the stance phase under the SV condition compared to the NSV condition. There were no differences in knee and hip joint angles between the visual conditions for both groups. CONCLUSIONS: When wearing stroboscopic glasses, CAI patients showed altered movement patterns, including increased inversion angle and peroneus longus activation during the stance phase of landing cutting. The results suggest that CAI patients may lack the ability to reweight sensory information to adapt their movement to visual disruption.

Decreased rate of torque development in ankle evertors for individuals with chronic ankle instability.

BACKGROUND: Individuals with chronic ankle instability have decreased peak torque during maximum voluntary contraction in ankle evertors/invertors, and hip abductors. However, it is unclear whether individuals with chronic ankle instability and/or copers demonstrate decreased rate of torque development in ankle evertors/invertors, and hip abductors. METHODS: 54 university-aged participants (18 chronic ankle instability, 18 copers, and 18 controls) performed three maximal isometric contractions for ankle evertors and invertors, and hip abductors. Rate of torque development was defined as the linear slope of the torque-time curve during the first 200 ms of each contraction and compared between the three groups using a one-way analysis of variance (α = 0.05). FINDINGS: The chronic ankle instability group showed 38.1% less rate of torque development than the coper (P = 0.03 and d = 0.84) and 37.1% than the control groups (P = 0.03 and d = 1.03) in the ankle evertors. For the hip abductors, there were moderate effects between the chronic ankle instability group and the copers (P = 0.06 and d = 0.70), and control groups (P = 0.06 and d = 0.75). INTERPRETATIONS: The observed between-groups differences in rate of torque development indicate that restoring rate of torque development after lateral ankle sprain may be important to reduce risk of reinjury and development of chronic ankle instability. Clinicians should consider the rate of torque development in the ankle evertors and hip abductors during rehabilitation chronic ankle instability patients.

Balance Training with Stroboscopic Glasses Alters Neuromechanics in Chronic Ankle Instability Patients during single leg drop.

CONTEXT: Therapeutic interventions for individuals with chronic ankle instability (CAI) patients are recommended to improve muscle strength, postural control, and range of motions. However, their effects on neuromechanics during a drop landing remain unclear. Additionally, even though therapeutic interventions with stroboscopic glasses appear to be effective in improving postural control, it remains unclear how the utilization of stroboscopic glasses during therapeutic interventions affects landing neuromechanics. OBJECTIVES: This study utilized balance training with stroboscopic glasses to identify its effect on neuromechanics during a single leg drop landing in CAI patients. DESIGN: A randomized controlled trial. SETTING: A controlled laboratory setting. PATIENTS OR OTHER PARTICIPANTS: Fifty people with CAI were randomly assigned to one of two groups: strobe group (n=25) or control group (n=25). The 4-week rehabilitation (three sessions a week) included hop-based tasks and one-leg stance. The strobe group wore stroboscopic glasses during the training, while the control group did not. MAIN OUTCOME MEASURE(S): Ankle, knee, hip kinematics, and 4 lower extremity muscle activations 150-ms before and after initial contact during a single leg drop landing in the two groups. RESULTS: The strobe group showed greater eversion (from 150-ms before to 30-ms after the initial contact) and dorsiflexion (from 30-ms to 96-ms after the initial contact) angles and peroneal longus (from 35-ms before to 5-ms after the initial contact) and tibialis anterior (from 0-ms to 120-ms after the initial contact) activation in the posttest compared to the pretest. CONCLUSIONS: CAI patients who underwent a 4-week rehabilitation with stroboscopic glasses demonstrated changes in neuromechanics including increased dorsiflexion and eversion ankle angles and tibialis anterior and peroneus longus activation during a single leg drop landing. This finding suggests that utilization of stroboscopic glasses during rehabilitation could be beneficial in helping CAI patients develop safe landing mechanics.

Unexpected inversion perturbation during a single-leg landing in patients with chronic ankle instability.

It remains unclear how unexpected perturbations during single-leg landings affect lower extremity kinematics and muscle activations in patients with chronic ankle instability (CAI). The purpose of this study was to identify the differences in lower extremity movement patterns among CAI subjects, copers, and healthy controls. Sixty-six people including 22 CAI subjects, 22 copers, and 22 healthy controls volunteered to participate in the study. Lower extremity joint kinematics and EMG activations from 200-ms pre to 200-ms post the initial contact during unexpected tilted landings were measured. Functional data analysis was used to evaluate between-group differences for outcome measures. Relative to copers and healthy controls, CAI subjects showed more inversion from 40-ms to 200-ms after initial contact. Relative to healthy controls, CAI subjects and copers showed more dorsiflexion. Relative to healthy controls, CAI subjects and copers showed more muscle activation in tibialis anterior and peroneus longus, respectively. In conclusion, CAI subjects demonstrated greater inversion angles and muscle activation before initial contact compared to LAS copers and healthy controls. This suggests that CAI subjects and copers prepare for their landing with protective movements, but the prepared movements shown by CAI subjects may be insufficient to reduce risk of recurrent injury.

Lower Extremity Energy Dissipation and Generation During Jump Landing and Cutting in Patients With Chronic Ankle Instability.

CONTEXT: Participants with chronic ankle instability (CAI) frequently display altered movement patterns during functional movements. However, it remains unclear how these altered joint kinematics during jump landing negatively affect ankle joint health in the CAI population. Calculating joint energetics may offer an important method to estimate the magnitude of lower extremity joint loading during functional movements in participants with CAI. OBJECTIVE: To determine differences in energy dissipation and generation by the lower extremity during maximal jump landing and cutting among groups with CAI, copers, and controls. DESIGN: Cross-sectional study. SETTING: Laboratory. PATIENTS OR OTHER PARTICIPANTS: Forty-four participants with CAI, 44 copers, and 44 controls. MAIN OUTCOME MEASURES(S): Kinematics and kinetics of the lower extremity and ground reaction force data were collected during a maximal jump-landing and cutting task. The product of angular velocity in the sagittal plane and joint moment data represented joint power. Energy dissipation and generation by the ankle, knee, and hip joints were calculated by integrating regions of the joint power curve. RESULTS: Participants with CAI displayed reduced ankle energy dissipation (35.9% ± 10.1%) and generation (31.6% ± 12.8%; P < .01) compared with copers (dissipation = 43.6% ± 11.1%; generation = 40.4% ± 12.0%) and controls (dissipation = 41.3% ± 11.1%; generation = 39.6% ± 12.0%) during maximal jump landing and cutting. Participants with CAI also displayed greater energy dissipation at the knee (45.1% ± 9.1%) than copers (39.7% ± 9.5%) during the loading phase and greater energy generation at the hip than controls (36.6% ± 16.8% versus 28.3% ± 12.8%) during the cutting phase. However, copers displayed no differences in joint energetics compared with controls. CONCLUSIONS: Participants with CAI displayed differences in both energy dissipation and generation by the lower extremity during maximal jump landing and cutting. However, copers did not show altered joint energetics, which may represent a coping mechanism to avoid further injuries.

Effect of varied dorsiflexion range of motion on landing biomechanics in chronic ankle instability.

BACKGROUND: Limited dorsiflexion range of motion (DFROM) is a risk factor for lateral ankle sprain. However, varied DFROM exists within the chronic ankle instability (CAI) population, and how the variability may influence altered movement patterns during landing is unclear. OBJECTIVE: The purpose of this study was to identify different movement strategies during maximal jump landing/cutting among CAI patients classified by varied DFROM. METHODS: One hundred CAI subjects were classified into 3 subgroups based on their DFROM, measured by the weight-bearing lunge test: a Hypo- (≤40°), Normal- (40-50°), and Hyper-DFROM group (≥50°). Participants completed five trials of maximal jump landing/cutting. Lower extremity joint angles and EMG activation of seven muscles were collected from initial contact to toe-off. Functional analyses of variance were used to evaluate between-group differences for these outcome variables. RESULTS: Hypo-DFROM group (14M, 10F) displayed the reduced ankle dorsiflexion and inversion angles with increased hip flexion angle as a compensatory kinematic chain movement strategy. In addition, motion restrictions of the ankle are associated with altered muscle activation in both distal and proximal muscles during landing/cutting. Normal-DFROM (25M, 30F) and Hyper-DFROM (11M, 10F) groups also have different movement strategies including greater inversion angle and less EMG activation, which could contribute to further ankle injuries. CONCLUSIONS: Our data suggest that limited DFROM negatively affects the ankle joint during demanding movement within the CAI population. These movement patterns in CAI patients with pathomechanical deficits could contribute to further ankle sprains.

Disrupted vision impairs force steadiness and accuracy in chronic ankle instability patients.

The primary purpose of this study was to examine the effect of visual disruption on submaximal force steadiness and accuracy among three groups including chronic ankle instability (CAI) patients, lateral ankle sprain copers, and healthy controls. Twenty patients with CAI, 20 copers, and 20 matched-healthy controls volunteered to participate in the study. Submaximal force steadiness and accuracy for evertors, invertors, and hip abductors (10% and 20% of their maximal voluntary isometric contraction) were measured with an isokinetic dynamometer. All groups performed the tasks with and without stroboscopic glasses. The CAI group showed worse steadiness and accuracy in evertors with visual disruption compared to nonvisual disruption (p < 0.0001 and = 0.02, respectively). Relative to the control group, the CAI group showed worse force steadiness and accuracy in evertors (p < 0.0001, both), worse force accuracy in hip abductors (p = 0.02), and the coper group also showed worse accuracy in evertors (p = 0.02). Individuals with CAI demonstrated impaired force steadiness and accuracy in evertors and hip abductors compared to healthy controls. In addition, they tended to rely more on visual feedback during the force steadiness task than copers and healthy controls.

The effects of visual feedback disruption on postural control with chronic ankle instability.

OBJECTIVES: The purpose of this study was to identify the effects of reduced visual feedback via stroboscopic glasses on dynamic postural control among chronic ankle instability (CAI), lateral ankle sprain (LAS) coper and uninjured control participants. DESIGN: Controlled trial in a laboratory setting. METHODS: Twenty CAI patients, 20 copers, and 20 controls participated in this study. Each participant performed a single-leg hop stabilization test with eyes open (EO) and stroboscopic vision (SV). Two-way ANOVAs (group × condition) were used to examine the differences between group (CAI, coper, and control) and condition (EO and SV). RESULTS: There was a significant group by condition interaction for DPSI scores. CAI patients displayed increased DPSI scores with SV compared to EO (p < 0.01), and CAI patients had increased DPSI scores only with SV when compared with controls. All participants displayed decreased dynamic postural control under the SV condition compared to the EO condition (p < 0.01) regardless of ankle group. CONCLUSIONS: CAI patients rely more on visual feedback during dynamic postural control than copers and controls. However, they may not be as able to compensate for the disrupted visual feedback during a dynamic task. Regardless of ankle injury history, stroboscopic glasses could be cost-effective visual disruption devices during a dynamic balance task.

A Review of the Relationships Between Knee Pain and Movement Neuromechanics.

CONTEXT: Knee injury and disease are common, debilitating, and expensive. Pain is a chief symptom of knee injury and disease and likely contributes to arthrogenic muscle inhibition. Joint pain alters isolated motor function, muscular strength, and movement biomechanics. Because knee pain influences biomechanics, it likely also influences long-term knee joint health. OBJECTIVE: The purpose of this article is 2-fold: (1) review effects of knee pain on lower-extremity muscular activation and corresponding biomechanics and (2) consider potential implications of neuromechanical alterations associated with knee pain for long-term knee joint health. Experimental knee pain is emphasized because it has been used to mimic clinical knee pain and clarify independent effects of knee pain. Three common sources of clinical knee pain are also discussed: patellofemoral pain, anterior cruciate ligament injury and reconstruction, and knee osteoarthritis. DATA SOURCES: The PubMed, Web of Science, and SPORTDiscus databases were searched for articles relating to the purpose of this article. CONCLUSION: Researchers have consistently reported that knee pain alters neuromuscular activation, often in the form of inhibition that likely occurs via voluntary and involuntary neural pathways. The effects of knee pain on quadriceps activation have been studied extensively. Knee pain decreases voluntary and involuntary quadriceps activation and strength and alters the biomechanics of various movement tasks. If allowed to persist, these neuromechanical alterations might change the response of articular cartilage to joint loads during movement and detrimentally affect long-term knee joint health. Physical rehabilitation professionals should consider neuromechanical effects of knee pain when treating knee injury and disease. Resolution of joint pain can likely help to restore normal movement neuromechanics and potentially improve long-term knee joint health and should be a top priority.

Effects of balance training with stroboscopic glasses on postural control in chronic ankle instability patients.

Individuals with chronic ankle instability (CAI) are believed to rely more on visual information during postural control due to impaired proprioceptive function, which may increase the risk of injury when their vision is limited during sports activities. OBJECTIVES: To compare (1) the effects of balance training with and without stroboscopic glasses on postural control and (2) the effects of the training on visual reliance in patients with CAI. DESIGN: A randomized controlled clinical trial. METHODS: Twenty-eight CAI patients were equally assigned to one of 2 groups: strobe or control group. The strobe group wore stroboscopic glasses during a 4-week balance training. Static postural control, a single-leg hop balance test calculated by Dynamic Postural Stability Index (DPSI), and the Y-Balance test (YBT) were measured. During the tests, there were different visual conditions: eyes-open (EO), eyes-closed (EC), and strobe vision (SV). Romberg ratios were then calculated as SV/EO, and EC/EO and used for statistical analysis. RESULTS: The strobe group showed a higher pretest-posttest difference in velocity in the medial-lateral direction and vertical stability index under SV compared with the control group (p < .05). The strobe group showed higher differences in EC/EO for velocity in the medial-lateral and anterior-posterior directions, and 95% confidence ellipse area (p < .05), and in SV/EO for velocity in the medial-lateral, 95% confidence ellipse area, and YBT-anterior direction (p < .05). CONCLUSION: The 4-week balance training with stroboscopic glasses appeared to be effective in improving postural control and altering visual reliance in patients with CAI.

Acute effect of whole-body vibration on electromechanical delay and vertical jump performance.

OBJECTIVES: To determine if a change in vertical jump performance from acute whole-body vibration can be explained by indirectly assessing spindle sensitivity from electromechanical delay. METHODS: Using a counter-balanced design, twenty college-aged participants performed whole-body vibration (WBV) and control treatments. WBV included 10 intervals (26 Hz, 3.6 mm) of 60 s in a half-squat followed by 60 s of rest. After 5 intervals, participants rested for 6-minutes before commencing the final 5 intervals. For the control, the exact same protocol of whole-body vibration was performed but without vibration. Electromechanical delay and vertical jump were assessed at baseline, during the 6-minute rest period and immediately after whole-body vibration and control. RESULTS: There were no differences between treatments, for both electromechanical delay (F(2, 38)=1.385, p=0.263) and vertical jump (F(2, 38)=0.040, p<0.96). Whole-body vibration had no effect on vertical jump performance. CONCLUSION: The current whole-body vibration protocol is not effective for acute vertical jump or electromechanical delay enhancement. Also, since there was no effect on electromechanical delay, this suggests that whole-body vibration did not enhance muscle spindle sensitivity for the parameters examined.

Anterior knee pain independently alters landing and jumping biomechanics.

Background Biomechanical effects of anterior knee pain are difficult to distinguish from effects of other factors also related to knee injury (e.g., joint effusion). The purpose of this study was to evaluate independent effects of anterior knee pain on landing and jumping biomechanics. Methods Thirteen healthy participants performed a land and jump movement task, under three experimental conditions (pre-pain, pain, and post-pain), during one data collection session. One 1-ml injection of hypertonic saline into the infrapatellar fat pad was used to induce experimental anterior knee pain during the pain condition. Participant-perceived anterior knee pain was measured every 2 min throughout data collection. Landing and jumping biomechanics were measured and compared between the experimental conditions using a functional statistical approach. Findings The aforementioned injection increased mean participant-perceived anterior knee pain, from zero during the pre-pain condition to 2.6 ± 0.71 cm during the pain condition. Vertical ground reaction force, knee flexion angle, and internal knee extension moment decreased by approximately 0.100 body weights, 3°, and 0.010 Nm/body weight × body height, respectively, between the pre-pain and pain conditions. Conversely, hip flexion angle and internal hip extension moment increased by approximately 3° and 0.006 Nm/body weight × body height, respectively, between the pre-pain and pain conditions. Several biomechanical changes persisted after anterior knee pain abatement (the post-pain condition). Interpretation Anterior knee pain alters landing and jumping biomechanics, independent of other injury-related factors. These altered biomechanics likely change knee joint loading patterns and might increase risk for chronic knee joint injury and/or pathology.

Submaximal Force Steadiness and Accuracy in Patients With Chronic Ankle Instability.

CONTEXT: Patients with chronic ankle instability (CAI) have demonstrated sensorimotor impairments. Submaximal force steadiness and accuracy measure sensory, motor, and visual function via a feedback mechanism, which helps researchers and clinicians comprehend the sensorimotor deficits associated with CAI. OBJECTIVE: To determine if participants with CAI experienced deficits in hip and ankle submaximal force steadiness and accuracy compared with healthy control participants. DESIGN: Case-control study. SETTING: Research laboratory. PATIENTS OR OTHER PARTICIPANTS: Twenty-one patients with CAI and 21 uninjured individuals. MAIN OUTCOME MEASURE(S): Maximal voluntary isometric contraction (MVIC) and force steadiness and accuracy (10% and 30% of MVIC) of the ankle evertors and invertors and hip abductors were assessed using the central 10 seconds (20%-87% of the total time) of the 3 trials. RESULTS: Relative to the control group, the CAI group demonstrated less accuracy of the invertors (P < .001). Across all motions, the CAI group showed less steadiness (P < .001) and less accuracy (P < .01) than the control group at 10% of MVIC. For MVIC, the CAI group displayed less force output in hip abduction than the uninjured group (P < .0001). CONCLUSIONS: Patients with CAI were unable to control ongoing fine force (10% and 30% of MVIC) through a feedback mechanism during an active test. These findings suggested that deficits in sensorimotor control predisposed patients with CAI to injury positions because they had difficulty integrating the peripheral information and correcting their movements in relation to visual information.

Simultaneous ice and transcutaneous electrical nerve stimulation decrease anterior knee pain during running but do not affect running kinematics or associated muscle inhibition.

BACKGROUND: Runners often experience anterior knee pain and this pain is associated with altered running neuromechanics. The purpose of this study was to examine potential therapeutic benefits (reduced pain and restored running neuromechanics) of simultaneously applied ice and transcutaneous electrical nerve stimulation on experimentally-induced anterior knee pain. METHODS: Nineteen healthy subjects completed a sham and treatment data collection session. For both sessions, hypertonic saline was infused into the infrapatellar fat pad for approximately 80 min to induce experimental anterior knee pain. Perceived pain levels were measured every two minutes and running neuromechanics were recorded at four time points: pre-pain, pain before treatment, pain immediately post-treatment, and pain 20 min post-treatment. FINDINGS: The saline infusion significantly increased perceived knee pain from 0 to 2.8 cm. The ice/transcutaneous electrical nerve stimulation treatment significantly reduced perceived knee pain by 35%, six minutes after the treatment initiation. Perceived knee pain remained reduced until eight minutes after the treatment termination. The knee pain significantly decreased peak gluteus medius, vastus lateralis, and vastus medialis activation during running, each by an average of 17% plus/minus 6%; however, none of these decreases were resolved via the therapeutic treatment. Neither the knee pain nor the therapeutic treatment significantly affected peak gluteus maximus activation or peak hip adduction angle. INTERPRETATION: The experimental pain model effectively produced anterior knee pain and decreased muscle activation during running. The simultaneous ice/transcutaneous electrical nerve stimulation treatment effectively decreased anterior knee pain, but did not restore running neuromechanics that were altered due to the pain.

Altered Movement Biomechanics in Chronic Ankle Instability, Coper, and Control Groups: Energy Absorption and Distribution Implications.

CONTEXT: Patients with chronic ankle instability (CAI) exhibit deficits in neuromuscular control, resulting in altered movement strategies. However, no researchers have examined neuromuscular adaptations to dynamic movement strategies during multiplanar landing and cutting among patients with CAI, individuals who are ankle-sprain copers, and control participants. OBJECTIVE: To investigate lower extremity joint power, stiffness, and ground reaction force (GRF) during a jump-landing and cutting task among CAI, coper, and control groups. DESIGN: Cross-sectional study. SETTING: Laboratory. PATIENTS OR OTHER PARTICIPANTS: A total of 22 patients with CAI (age = 22.7 ± 2.0 years, height = 174.6 ± 10.4 cm, mass = 73.4 ± 12.1 kg), 22 ankle-sprain copers (age = 22.1 ± 2.1 years, height = 173.8 ± 8.2 cm, mass = 72.6 ± 12.3 kg), and 22 healthy control participants (age = 22.5 ± 3.3 years, height = 172.4 ± 13.3 cm, mass = 72.6 ± 18.7 kg). INTERVENTION(S): Participants performed 5 successful trials of a jump-landing and cutting task. MAIN OUTCOME MEASURE(S): Using motion-capture cameras and a force plate, we collected lower extremity ankle-, knee-, and hip-joint power and stiffness and GRFs during the jump-landing and cutting task. Functional analyses of variance were used to evaluate between-groups differences in these dependent variables throughout the contact phase of the task. RESULTS: Compared with the coper and control groups, the CAI group displayed (1) up to 7% of body weight more posterior and 52% of body weight more vertical GRF during initial landing followed by decreased GRF during the remaining stance and 22% of body weight less medial GRF across most of stance; (2) 8.8 W/kg less eccentric and 3.2 W/kg less concentric ankle power, 6.4 W/kg more eccentric knee and 4.8 W/kg more eccentric hip power during initial landing, and 5.0 W/kg less eccentric knee and 3.9 W/kg less eccentric hip power; and (3) less ankle- and knee-joint stiffness during the landing phase. Concentric power patterns were similar to eccentric power patterns. CONCLUSIONS: The CAI group demonstrated altered neuromechanics, redistributing energy absorption from the distal (ankle) to the proximal (knee and hip) joints, which coincided with decreased ankle and knee stiffness during landing. Our data suggested that although the coper and control groups showed similar landing and cutting strategies, the CAI group used altered strategies to modulate impact forces during the task.

Characterization of Multiple Movement Strategies in Participants With Chronic Ankle Instability.

CONTEXT: Chronic ankle instability (CAI) is characterized by multiple sensorimotor deficits, affecting strength, postural control, motion, and movement. Identifying specific deficits is the key to developing appropriate interventions for this patient population; however, multiple movement strategies within this population may limit the ability to identify specific movement deficits. OBJECTIVE: To identify specific movement strategies in a large sample of participants with CAI and to characterize each strategy relative to a sample of uninjured control participants. DESIGN: Descriptive laboratory study. SETTING: Biomechanics laboratory. PATIENTS OR OTHER PARTICIPANTS: A total of 200 individuals with CAI (104 men, 96 women; age = 22.3 ± 2.2 years, height = 174.2 ± 9.5 cm, mass = 72.0 ± 14.0 kg) were selected according to the inclusion criteria established by the International Ankle Consortium and were fit into clusters based on movement strategy. A total of 100 healthy individuals serving as controls (54 men, 46 women; age = 22.2 ± 3.0 years, height = 173.2 ± 9.2 cm, mass = 70.7 ± 13.4 kg) were compared with each cluster. MAIN OUTCOME MEASURE(S): Lower extremity joint biomechanics and ground reaction forces were collected during a maximal vertical jump landing, followed immediately by a side cut. Data were reduced to functional output or curves, kinematic data from the frontal and sagittal planes were reduced to a single representative curve for each plane, and representative curves were clustered using a Bayesian clustering technique. Estimated functions for each dependent variable were compared with estimated functions from the control group to describe each cluster. RESULTS: Six distinct clusters were identified from the frontal-plane and sagittal-plane data. Differences in joint angles, joint moments, and ground reaction forces between clusters and the control group were also identified. CONCLUSIONS: The participants with CAI demonstrated 6 distinct movement strategies, indicating that CAI could be characterized by multiple distinct movement alterations. Clinicians should carefully evaluate patients with CAI for sensorimotor deficits and quality of movement to determine the appropriate interventions for treatment.