Relationships Between Running Biomechanics and Femoral Articular Cartilage Thickness and Composition in Anterior Cruciate Ligament Reconstruction Patients.

BACKGROUND: Although individuals with anterior cruciate ligament reconstruction (ACLR) are at high risk for posttraumatic osteoarthritis, mechanisms underlying the relationship between running and knee cartilage health remain unclear. OBJECTIVE: We aimed to investigate how 30 min of running influences femoral cartilage thickness and composition and their relationships with running biomechanics in patients with ACLR and controls. METHODS: Twenty patients with ACLR (time post-ACLR: 14.6 ± 6.1 months) and 20 matched controls participated in the study. A running session required both groups to run for 30 min at a self-selected speed. Before and after running, we measured femoral cartilage thickness via ultrasound imaging. A MRI session consisted of T2 mapping. RESULTS: The ACLR group showed longer T2 relaxation times in the medial femoral condyle at resting compared with the control group (central: 51.2 ± 16.6 vs. 34.9 ± 13.2 ms, p = 0.006; posterior: 50.2 ± 10.1 vs. 39.8 ± 7.4 ms, p = 0.006). Following the run, the ACLR group showed greater deformation in the medial femoral cartilage than the control group (0.03 ± 0.01 vs. 0.01 ± 0.01 cm, p = 0.001). Additionally, the ACLR group showed significant negative correlations between resting T2 relaxation time in the medial femoral condyle and vertical impulse (standardized regression coefficients = -0.99 and p = 0.004) during running. CONCLUSIONS: Our findings suggest that those who are between 6 and 24 months post-ACLR have degraded cartilage composition and their cartilage deforms more due to running vGRF.

Effects of Chronic Pain on Static and Dynamic Postural Control in Chronic Ankle Instability.

OBJECTIVE: To identify the effects of chronic pain levels on static and dynamic postural (DP) control in individuals with chronic ankle instability (CAI). DESIGN: Cross-sectional study. SETTING: Controlled laboratory. PARTICIPANTS: Sixty participants were divided into the following 3 groups: 20 high pain individuals with CAI (high pain), 20 low pain individuals with CAI (low pain), and 20 healthy controls (control). INDEPENDENT VARIABLES: Groups (CAI with high pain, CAI with low pain, and control) and visual conditions (eyes open and closed) for single-leg stance. MAIN OUTCOME MEASURES: Participants performed single-leg stance with eyes open and closed, the star excursion balance test, and single-leg hop to stabilization. RESULTS: The high pain group experienced worse self-reported outcomes, including Foot and Ankle Ability Measure activities of daily living and sports, than the low pain and control groups. Regardless of visual condition, both the high and low pain groups exhibited decreased static postural control in mediolateral (ML) compared with the control group. Specifically, the high pain group showed decreased static postural control in ML under closed eyes compared with the low pain and the control groups. The high pain group showed less reach distance than the control group and increased DP control in vertical and overall DP stability index compared with the low and control groups. CONCLUSIONS: Chronic pain can significantly affect both static and DP control in individuals with CAI. Therefore, clinicians should consider chronic pain as one of the factors affecting postural control in individuals with CAI.

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.

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.

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.

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.

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.

Efficacy of Sensory Transcutaneous Electrical Nerve Stimulation on Perceived Pain and Gait Patterns in Individuals With Experimental Knee Pain.

OBJECTIVES: To examine the effect of experimental knee pain on perceived knee pain and gait patterns and to examine the efficacy of transcutaneous electrical nerve stimulation (TENS) on perceived knee pain and pain-induced knee gait mechanics. DESIGN: Crossover trial. SETTING: Biomechanics laboratory. PARTICIPANTS: Recreationally active, individuals without musculoskeletal pain aged 18 to 35 years (N=30). INTERVENTIONS: Thirty able-bodied individuals were assigned to either a TENS (n=15) or a placebo (n=15) group. All participants completed 3 experimental sessions in a counterbalanced order separated by 2 days: (1) hypertonic saline infusion (5% NaCl); (2) isotonic saline infusion (0.9% NaCl); and (3) control. Each group received sensory electrical stimulation or placebo treatment for 20 minutes, respectively. MAIN OUTCOME MEASURES: Perceived pain was collected every 2 minutes using a 10-cm visual analog scale (VAS) for 50 minutes and analyzed using a mixed model analysis of covariance with repeated measures. Gait analyses were performed at baseline, infusion, and treatment. Sagittal and frontal knee angles and internal net joint torque across the entire stance were analyzed using a functional data analysis approach. RESULTS: Hypertonic saline infusion increased perceived pain (4/10cm on a VAS; P<.05) and altered right knee angle (more flexion and less abduction; P<.05) and internal net joint torque (less extension and greater abduction; P<.05) across various stance phases. TENS treatment reduced perceived pain and improved right sagittal gait abnormalities as compared with placebo treatment (P<.05). CONCLUSIONS: This pain model increases perceived pain and induces compensatory gait patterns in a way that indicates potential quadriceps weakness. However, TENS treatment effectively reduces perceived pain and restores pain-induced gait abnormalities in sagittal knee mechanics.

Effects of Experimental Anterior Knee Pain on Muscle Activation During Landing and Jumping Performed at Various Intensities.

CONTEXT: Although knee pain is common, some facets of this pain are unclear. The independent effects (ie, independent from other knee injury or pathology) of knee pain on neural activation of lower-extremity muscles during landing and jumping have not been observed. OBJECTIVE: To investigate the independent effects of knee pain on lower-extremity muscle (gastrocnemius, vastus medialis, medial hamstrings, gluteus medius, and gluteus maximus) activation amplitude during landing and jumping, performed at 2 different intensities. DESIGN: Laboratory-based, pretest, posttest, repeated-measures design, where all subjects performed both data-collection sessions. METHODS: Thirteen able-bodied subjects performed 2 different land and jump tasks (forward and lateral) under 2 different conditions (control and pain), at 2 different intensities (high and low). For the pain condition, experimental knee pain was induced via a hypertonic saline injection into the right infrapatellar fat pad. Functional linear models were used to evaluate the influence of experimental knee pain on muscle-activation amplitude throughout the 2 land and jump tasks. RESULTS: Experimental knee pain independently altered activation for all of the observed muscles during various parts of the 2 different land and jump tasks. These activation alterations were not consistently influenced by task intensity. CONCLUSION: Experimental knee pain alters activation amplitude of various lower-extremity muscles during landing and jumping. The nature of the alteration varies between muscles, intensities, and phases of the movement (ie, landing and jumping). Generally, experimental knee pain inhibits the gastrocnemius, medial hamstring, and gluteus medius during landing while independently increasing activation of the same muscles during jumping.

Running decreases knee intra-articular cytokine and cartilage oligomeric matrix concentrations: a pilot study.

INTRODUCTION: Regular exercise protects against degenerative joint disorders, yet the mechanisms that underlie these benefits are poorly understood. Chronic, low-grade inflammation is widely implicated in the onset and progression of degenerative joint disease. PURPOSE: To examine the effect of running on knee intra-articular and circulating markers of inflammation and cartilage turnover in healthy men and women. METHODS: Six recreational runners completed a running (30 min) and control (unloaded for 30 min) session in a counterbalanced order. Synovial fluid (SF) and serum samples were taken before and after each session. Cytokine concentration was measured in SF and serum using a multiplexed cytokine magnetic bead array. Ground reaction forces were measured during the run. RESULTS: There were no changes in serum or SF cytokine concentration in the control condition. The cytokine GM-CSF decreased from 10.7 ± 9.8 to 6.2 ± 5.9 pg/ml pre- to post-run (p = 0.03). IL-15 showed a trend for decreasing concentration pre- (6.7 ± 7.5 pg/ml) to post-run (4.3 ± 2.7 pg/ml) (p = 0.06). Changes in IL-15 concentration negatively correlated with the mean number of foot strikes during the run (r 2 = 0.67; p = 0.047). The control condition induced a decrease in serum COMP and an increase in SF COMP, while conversely the run induced an increase in serum COMP and a decrease in SF COMP. Changes in serum and SF COMP pre- to post-intervention were inversely correlated (r 2 = 0.47; p = 0.01). CONCLUSIONS: Running appears to decrease knee intra-articular pro-inflammatory cytokine concentration and facilitates the movement of COMP from the joint space to the serum.

Shoulder-muscle electromyography during shoulder external-rotation exercises with and without slight abduction.

CONTEXT: Standing and side-lying external-rotation exercises produce high activation of the deltoid and infraspinatus. Slight shoulder abduction during these exercises may decrease deltoid activity and increase infraspinatus activity. OBJECTIVE: To determine if the addition of a towel under the arm during standing and side-lying external rotation affects infraspinatus, middle and posterior deltoid, and pectoralis major activation characteristics compared with a no-towel condition. DESIGN: Controlled laboratory study. PARTICIPANTS: 20 male volunteers (age 26 ± 3 y, height 1.80 ± 0.07 m, mass 77 ± 10 kg) who were right-hand dominant and had bilaterally healthy shoulders with no current cervical pathology and no skin infection or shoulder lesion. INTERVENTIONS: External-rotation exercises without a towel roll (0° shoulder abduction) and with a towel roll (30° shoulder abduction) were performed in a standing and side-lying. MAIN OUTCOME MEASURES: Maximal voluntary isometric contraction for the infraspinatus, middle and posterior deltoid, and pectoralis major and external rotation in standing and side-lying with and without a towel roll were performed. Normalized average and peak surface EMG amplitude were compared between the towel conditions during standing and side-lying external rotation. RESULTS: Both infraspinatus and pectoralis major activity had no significant differences between the towel conditions in standing and side-lying (P > .05). In standing and side-lying, posterior-deltoid activity was significantly greater with a towel roll (P < .05). Middle-deltoid activity had no significant differences between the towel conditions in standing (P > .05). However, in side-lying, middle-deltoid activity was significantly lower with a towel roll (P < .05). CONCLUSION: Middle-deltoid activity decreased with a towel roll during side-lying exercises. More data are needed to determine if a towel roll could be used to potentially reduce superior glide during external-rotation exercises.

Body weight independently affects articular cartilage catabolism.

Although obesity is associated with osteoarthritis, it is unclear whether body weight (BW) independently affects articular cartilage catabolism (i.e., independent from physiological factors that also accompany obesity). The primary purpose of this study was to evaluate the independent effect of BW on articular cartilage catabolism associated with walking. A secondary purpose was to determine how decreased BW influenced cardiovascular response due to walking. Twelve able-bodied subjects walked for 30 minutes on a lower-body positive pressure treadmill during three sessions: control (unadjusted BW), +40%BW, and -40%BW. Serum cartilage oligomeric matrix protein (COMP) was measured immediately before (baseline) and after, and 15 and 30 minutes after the walk. Heart rate (HR) and rate of perceived exertion (RPE) were measured every three minutes during the walk. Relative to baseline, average serum COMP concentration was 13% and 5% greater immediately after and 15 minutes after the walk. Immediately after the walk, serum COMP concentration was 14% greater for the +40%BW session than for the -40%BW session. HR and RPE were greater for the +40%BW session than for the other two sessions, but did not differ between the control and -40%BW sessions. BW independently influences acute articular cartilage catabolism and cardiovascular response due to walking: as BW increases, so does acute articular cartilage catabolism and cardiovascular response. These results indicate that lower-body positive pressure walking may benefit certain individuals by reducing acute articular cartilage catabolism, due to walking, while maintaining cardiovascular response. Key pointsWalking for 30 minutes with adjustments in body weight (normal body weight, +40% and -40% body weight) significantly influences articular cartilage catabolism, measured via serum COMP concentration.Compared to baseline levels, walking with +40% body weight and normal body weight both elicited significant increases in articular cartilage catabolism, while walking with -40% body weight did not.Cardiovascular response (HR and RPE) was not significantly different during walking with normal body weight and when compared to walking with -40% body weight.

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.

Induced anterior knee pain immediately reduces involuntary and voluntary quadriceps activation.

OBJECTIVE: To examine the immediate effects of experimentally induced anterior knee pain (AKP) on involuntary and voluntary quadriceps strength and activation. DESIGN: Crossover 3 × 3 randomized controlled laboratory study with repeated measures. SETTING: Human Performance Research Center, Brigham Young University. PARTICIPANTS: Thirteen neurologically sound volunteers (age, 21.9 ± 3.2 years). INTERVENTIONS: Subjects underwent 3 different conditions (pain, sham, and control). To induce AKP and sham condition, 5% sodium chloride and 0.9% sodium chloride (total volume of 1.0 mL for each condition), respectively, were injected into the infrapatellar fat pad on the dominant leg. No injection was performed for the control condition. MAIN OUTCOME MEASURES: The vastus medialis peak Hoffmann reflex normalized by the peak motor response (H:M ratio) was used to measure involuntary quadriceps activation. Quadriceps central activation ratio (CAR) using maximal isometric knee extension torque (N·m) was calculated to assess voluntary quadriceps activation. The visual analog scale was used to measure pain perception. RESULTS: Our pain model increased perceived pain immediately after the 5% hypertonic saline injection and pain lasted for 12 minutes on average (F40,743 = 16.85, P < 0.001). During the pain condition, subjects showed a 12% decrease in H:M ratio (F2,59 = 8.64, P < 0.001), a 34% decrease in maximal isometric knee extension torque (F2,59 = 5.89, P < 0.01), and a 5% decrease in CAR (F2,59 = 3.83, P = 0.03). CONCLUSIONS: Our data showed that joint pain may be an independent factor to alter function of the muscles surrounding the painful joint. Both involuntary and voluntary inhibitory pathways may play a role in an immediate reduction of muscle activation.

Within- and between-session reliability of the maximal voluntary knee extension torque and activation.

A ratio between the torque generated by maximal voluntary isometric contraction (MVIC) and exogenous electrical stimulus, central activation ratio (CAR), has been widely used to assess quadriceps function. To date, no data exist regarding between-session reliability of this measurement. Thirteen neurologically sound volunteers underwent three testing sessions (three trials per session) with 48 hours between-session. Subjects performed MVICs of the quadriceps with the knee locked at 90° flexion and the hip at 85°. Once the MVIC reached a plateau, an electrical stimulation from superimposed burst technique (SIB: 125 V with peak output current 450 mA) was manually delivered and transmitted directly to the quadriceps via stimulating electrodes. CAR was calculated by using the following equation: CAR = MVIC torque/MVIC + SIB torque. Intraclass correlation coefficients (ICC) were calculated within- (ICC((2,1))) and between-session (ICC((2,k))) for MVIC torques and CAR values. Our data show that quadriceps MVIC and CAR are very reliable both within- (ICC((2,1)) = 0.99 for MVIC; 0.94 for CAR) and between-measurement sessions (ICC((2,k)) = 0.92 for MVIC; 0.86 for CAR) in healthy young adults. For clinical research, more data of the patients with pathological conditions are required to ensure reproducibility of calculation of CAR.

Contributions of muscle fatigue to a neuromuscular neck injury in female ballroom dancers.

OBJECTIVE: To investigate the etiology of a loss-of-control neck injury in international modern (IM) dancesport dancers. A comparison to identify if dancers with neck injury have a greater decrease in median frequency in electromyography (EMG) than non-injured dancers. SUBJECTS: Twenty female subjects (mean age 21.6 ± 3.0 yrs, height 167.1 ± 4.3 cm, weight 59.1 ± 5.2 kg, mean BMI 21.1 ± 1.2) with minimum 1-year experience in competitive IM dancesport. measurements: EMG activity from the left upper trapezius, left splenius capitius, and right sternocleidomastoid muscles before and after dancing the five IM dances. Extension, lateral flexion, and neck length were also measured. RESULTS: There was no significant difference in all measurements. CONCLUSIONS: Although we did not find the etiology of this neck injury, this was the first research into this injury. Future research could study the different IM dances, compare different competition levels, or the amount of force placed on the neck when dancing.

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.

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.

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.