An Absence of Persistent Postural Stability Deficits Following a Sport Concussion in Collegiate Athletes.

OBJECTIVE: The purpose of our study was to determine whether persistent postural stability deficits exist in athletes following sport concussion (SC) in comparison with preinjury (baseline) values using Sample Entropy (SampEn). SETTING: Sports medicine clinic. PATIENTS OR OTHER PARTICIPANTS: Participants consisted of 71 collegiate athletes (44 male, 27 female) with an average age of 19.9 ± 0.96 years who had a history of 1 concussion that occurred during their time as a collegiate athlete. DESIGN: In our prospective, cohort design participants completed the Sensory Organization Test (SOT) at baseline, upon reporting symptom-free following a diagnosed SC, and upon establishing a new baseline prior to the start of the subsequent sport season. MAIN OUTCOME MEASURES: The SOT's condition scores were calculated and analyzed in alignment with the manufacturer's instructions. SampEn was calculated in the anterior-posterior (AP) and medial-lateral (ML) directions from the center-of-pressure oscillations over the 20-second time series for each SOT condition. The SOT and SampEn outcome scores for each condition were analyzed with repeated-measures analyses of variance. RESULTS: Significant main effects were observed for the SOT's conditions 3 ( F1.6, 114.8 = 7.83, P = .001, η2 = 0.10 [0.02-0.20]), 5 ( F1.8, 126.8 = 11.53, P < .001, η2 = 0.14 [0.04-0.25]), and 6 ( F1.9, 134.5 = 25.11, P < .001, η2 = 0.26 [0.14-0.37]), with significant improvements across time. Significant main effects were also observed for SampEn in the AP direction for conditions 3 ( F2, 140 = 7.59, P = .001, η2 = 0.10 [0.02-0.19]) and 6 ( F2, 140 = 6.22, P = .003, η2 = 0.08 [0.011-0.170]), with significant improvements across time. CONCLUSIONS: Following a diagnosed SC, our results suggest that collegiate athletes returned if not exceeded baseline values at the symptom-free and new baseline assessments. The application of linear and nonlinear measures of postural stability following a SC yielded similar outcomes in conjunction with a baseline assessment. Our findings support the clinical utility of the baseline SC assessment when evaluating persisting balance deficits when using linear or nonlinear measures.

Gluteal Activity During Gait in Patients With Chronic Ankle Instability Following Rehabilitation: A Randomized Controlled Trial.

CONTEXT: Ankle positioning gait biofeedback (GBF) has improved ankle inversion for patients with chronic ankle instability. However, the effects on proximal deficits remain unknown. The purpose of this study was to determine the effects of impairment-based rehabilitation with GBF and without biofeedback on gluteal activity during walking in patients with chronic ankle instability. DESIGN: Randomized controlled trial. METHODS: Eighteen patients with chronic ankle instability (14 women and 4 men; age 22 [4] y; height 171 [10] cm; mass 71.6 [13.8] kg) were recruited from a university setting, following International Ankle Consortium guidelines. Patients were randomly allocated to GBF or without biofeedback groups (N = 9 per group). Both groups performed 4 weeks of exercises and treadmill walking. The GBF group alone received feedback on frontal ankle positioning at initial contact during walking. Ultrasound videos of the gluteus maximus and medius were recorded during walking at baseline and follow-up by a blinded clinician. Gluteal activity ratios were obtained at each 10% of the gait cycle. Statistical parametric mapping repeated-measures analysis of variance were used to compare groups and time points. RESULTS: Both groups demonstrated significantly increased gluteus medius activity across the gait cycle compared with baseline (P < .01, mean differences: 0.13-0.21, Hedge g: 0.97-1.89); however, there were no significant between-group differences. There were no statistically significant changes noted for the gluteus maximus. No adverse events were observed. CONCLUSIONS: Impairment-based rehabilitation led to increased gluteus medius activity, but GBF did not provide any additional improvement to this parameter. Clinicians may consider implementing impairment-based strengthening interventions to improve gluteus medius function during gait for patients with CAI.

Effects of Midfoot Joint Mobilization on Perceived Ankle-Foot Function in Chronic Ankle Instability: A Crossover Clinical Trial.

CONTEXT: To investigate the effects of midfoot joint mobilization and a 1-week home exercise program, compared with a sham intervention, and home exercise program on pain, patient-reported outcomes, ankle-foot joint mobility, and neuromotor function in young adults with chronic ankle instability. DESIGN: Crossover clinical trial. METHODS: Twenty participants with chronic ankle instability were instructed in a stretching, strengthening, and balance home exercise program and were randomized a priori to receive either midfoot joint mobilizations (forefoot supination, cuboid glide, and plantar first tarsometatarsal) or a sham laying of hands on the initial visit. Changes in foot morphology, joint mobility, strength, dynamic balance, and patient-reported outcomes assessing pain, physical, and psychological function were assessed pre to post treatment and 1 week following post treatment. Participants crossed over to receive the alternate treatment and were assessed pre to post treatment and 1 week following. Linear modeling was used to assess changes in outcomes. RESULTS: Participants demonstrated significantly greater perceived improvement immediately following midfoot mobilization in the single assessment numeric evaluation (sham: 5.0% [10.2%]; mobilization: 43.9% [26.2%]; ß: 6.8; P < .001; adj R2: .17; Hedge g: 2.09), and global rating of change (sham: -0.1 [1.1]; mobilization: 1.1 [3.0]; ß: 1.8; P = .01; adj R2: .12; Hedge g: 0.54), and greater improved 1-week outcomes in rearfoot inversion mobility (sham: 4.4° [8.4°]; mobilization: -1.6° [6.1°]; ß: -6.37; P = .01; adj R2: .19; Hedge g: 0.81), plantar flexion mobility (sham: 2.7° [6.4°]; mobilization: -1.7° [4.3°]; ß: -4.36; P = .02; adj R2: .07; Hedge g: 0.80), and posteromedial dynamic balance (sham: 2.4% [5.9%]; mobilization: 6.0% [5.4%]; ß: 3.88; P = .04; adj R2: .10; Hedge g: 0.59) compared to the sham intervention. CONCLUSION: Greater perceived improvement and physical signs were observed following midfoot joint mobilization.

Self-Reported Injury History and Health-Related Quality of Life in Competitive, Collegiate Baton Twirlers.

OBJECTIVE: Injury epidemiology and health-related quality of life (HRQOL) have not been researched in baton twirlers. This cross-sectional study described time-loss injuries sustained by competitive collegiate baton twirlers, identified the relationship between training volume and injuries, and established injury impact on HRQOL. METHODS: An online survey was used to collect activity volume, number and characteristics of time-loss injuries experienced within a 12-month window, and HRQOL via the Short Form-36. Current injury status was addressed to place participants into categories: no injury history (No Injury), history of injury but no symptoms (Injury Hx, No Sx), and currently injured (Current Injury). RESULTS: One hundred forty-two participants met the inclusion criteria. One hundred twenty-eight (90%) participants experienced a time-loss injury with 295 total reported injuries (2.1±1.4; range 1-9 injuries). Sixty-two percent of all reported injuries were still producing symptoms. There was a high average reported injury severity score (6.3±2.3). The most commonly affected area was the hip/thigh (30%), followed by the knee (15%) and ankle (14%). The Current Injury group had worse SF-36 bodily pain (p=0.003), vitality domains (p=0.001), and physical composite score (p=0.015) compared to the No Injury group. Both the No Injury and Injury Hx, No Sx groups performed better than the Current Injury group on physical function (p=0.007 and 0.02, respectively). CONCLUSION: Competitive collegiate baton twirlers experience the majority of injuries in the lower extremity which cause prolonged physical and non-physical symptoms.

Gait biofeedback and impairment-based rehabilitation for chronic ankle instability.

Our purpose was to analyze the effects of 4 weeks of visual gait biofeedback (GBF) and impairment-based rehabilitation on gait biomechanics and patient-reported outcomes (PROs) in individuals with chronic ankle instability (CAI). Twenty-seven individuals with CAI participated in this randomized controlled trial (14 received no biofeedback (NBF), 13 received GBF). Both groups received 8 sessions of impairment-based rehabilitation. The GBF group received visual biofeedback to reduce ankle frontal plane angle at initial contact (IC) during treadmill walking. The NBF group walked for equal time during rehabilitation but without biofeedback. Dependent variables included three-dimensional kinematics and kinetics at the ankle, knee, and hip, electromyography amplitudes of 4 lower extremity muscles (tibialis anterior, fibularis longus, medial gastrocnemius, and gluteus medius), and PROs (Foot and Ankle Ability Measure Activities of Daily Living (FAAM-ADL), FAAM-Sport, Tampa Scale of Kinesiophobia (TSK), and Global Rating of Change (GROC)). The GBF group significantly decreased ankle inversion at IC (MD:-7.3º, g = 1.6) and throughout the entire stride cycle (peak inversion: MD:-5.9º, g = 1.2). The NBF group did not have significantly altered gait biomechanics. The groups were significantly different after rehabilitation for the FAAM-ADL (GBF: 97.1 ± 2.3%, NBF: 92.0 ± 5.7%), TSK (GBF: 29.7 ± 3.7, NBF: 34.9 ± 5.8), and GROC (GBF: 5.5 ± 1.0, NBF:3.9 ± 2.0) with the GBF group showing greater improvements than the NBF group. There were no significant differences between groups for kinetics or electromyography measures. The GBF group successfully decreased ankle inversion angle and had greater improvements in PROs after intervention compared to the NBF group. Impairment-based rehabilitation combined with visual biofeedback during gait training is recommended for individuals with CAI.

Mood, Psychological, and Behavioral Factors of Health-Related Quality of Life Throughout Recovery From Sport Concussion.

OBJECTIVE: To measure alterations in mood, psychological, and behavioral factors in collegiate athletes throughout recovery from sport concussion (SC) compared with matched controls. SETTING: University research laboratory. PARTICIPANTS: Twenty (55% female) division I collegiate athletes with SC (19.3 ± 1.08 years old, 1.77 ± 0.11 m, 79.6 ± 23.37 kg) and 20 (55% female) uninjured matched controls (20.8 ± 2.17 years old, 1.77 ± 0.10 m, 81.9 ± 23.45 kg). DESIGN: Longitudinal case control. MAIN MEASURES: Self-reported concussion-related symptoms, anxiety, resilience, stigma, sleep disturbance, fatigue, and appetite were assessed at 3 time points in the SC group: T1 (≤72 hours of SC), T2 (7 days after T1), and TF (after symptom resolution). Control participants were evaluated at similar intervals. Group and group-by-sex differences were assessed using repeated-measures analyses of variance. Post hoc analyses were performed with Tukey's honestly significant difference (HSD) and paired-sample t tests. RESULTS: The SC group had greater sleep disturbance than controls at T1 (P = .001; d = 1.21) and endorsed greater stigma at all time points (P ≤ .03; d ≥ 0.80). Stigma (F(2) = 3.68; P = 0.03; η2p = 0.12), sleep disturbance (F(2) = 5.27; P = .008; η2p = 0.15), and fatigue (F(2) = 3.46; P = .04; η2p = 0.11) improved throughout recovery in those with SC only. No differences were observed between males and females (P > .05). CONCLUSION: Sleep disturbance and stigma were negatively affected by SC, highlighting potential areas for clinical interventions to maximize recovery in males and females.

Ultrasound Measures of Intrinsic Foot Muscle Size and Activation Following Lateral Ankle Sprain and Chronic Ankle Instability.

CONTEXT: Tibial nerve impairment and reduced plantarflexion, hallux flexion, and lesser toe flexion strength have been observed in individuals with recent lateral ankle sprain (LAS) and chronic ankle instability (CAI). Diminished plantar intrinsic foot muscles (IFMs) size and contraction are a likely consequence. OBJECTIVES: To assess the effects of ankle injury on IFM size at rest and during contraction in young adults with and without LAS and CAI. SETTING: Laboratory. DESIGN: Cross-sectional. PATIENTS: A total of 22 healthy (13 females; age = 19.6 [0.9], body mass index [BMI] = 22.5 [3.2]), 17 LAS (9 females; age = 21.8 [4.1], BMI = 24.1 [3.7]), 21 Copers (13 females; age = 20.8 [2.9], BMI = 23.7 [2.9]), and 20 CAI (15 females; age = 20.9 [4.7], BMI = 25.1 [4.5]). MAIN OUTCOME MEASURES: Foot Posture Index (FPI), Foot Mobility Magnitude (FMM), and ultrasonographic cross-sectional area of the abductor hallucis, flexor digitorum brevis, quadratus plantae, and flexor hallucis brevis were assessed at rest, and during nonresisted and resisted contraction. RESULTS: Multiple linear regression analyses assessing group, sex, BMI, FPI, and FMM on resting and contracted IFM size found sex (B = 0.45; P < .001), BMI (B = 0.05; P = .01), FPI (B = 0.07; P = .05), and FMM × FPI interaction (B = -0.04; P = .008) accounted for 19% of the variance (P = .002) in resting abductor hallucis measures. Sex (B = 0.42, P < .001) and BMI (B = 0.03, P = .02) explained 24% of resting flexor digitorum brevis measures (P < .001). Having a recent LAS (B = 0.06, P = .03) and FMM (B = 0.04, P = .02) predicted 11% of nonresisted quadratus plantae contraction measures (P = .04), with sex (P < .001) explaining 13% of resting quadratus plantae measures (B = 0.24, P = .02). Both sex (B = 0.35, P = .01) and FMM (B = 0.15, P = .03) predicted 16% of resting flexor hallucis brevis measures (P = .01). There were no other statistically significant findings. CONCLUSIONS: IFM resting ultrasound measures were primarily determined by sex, BMI, and foot phenotype and not injury status. Routine ultrasound imaging of the IFM following LAS and CAI cannot be recommended at this time but may be considered if neuromotor impairment is suspected.

Gaze Accuracy Differences During Single-Leg Balance Following Anterior Cruciate Ligament Reconstruction.

CONTEXT: Individuals following anterior cruciate ligament reconstruction (ACLR) demonstrate altered postural stability and functional movement patterns. It is hypothesized that individuals following ACLR may compensate with sensory adaptations with greater reliance on visual mechanisms during activities. It is unknown if visual compensatory strategies are implemented to maintain postural stability during functional tasks. OBJECTIVE: To examine visual gaze accuracy during a single-leg balance task in individuals following ACLR compared with healthy, active controls. DESIGN: Case control. SETTING: Controlled laboratory. PARTICIPANTS: A total of 20 individuals (10 ACLR and 10 healthy controls) participated in the study. DATA COLLECTION AND ANALYSIS: Visual gaze patterns were obtained during 20-second single-leg balance trials while participants were instructed to look at presented targets. During the Stationary Target Task, the visual target was presented in a central location for the duration of the trial. The Moving Target Task included a visual target that randomly moved to 1 of 9 target locations for a period of 2 seconds. Targets were stratified into superior, middle, and inferior levels for the Moving Target Task. RESULTS: The Stationary Target Task demonstrated no differences in visual error between groups (P = .89). The Moving Target Task demonstrated a significant interaction between group and target level (F2,36 = 3.76, P = .033). Individuals following ACLR demonstrated greater visual error for the superior targets (ACLR = .70 [.44] m, healthy = .41 [.21] m, Cohen d = 0.83 [0.06 to 1.60]) and inferior targets (ACLR = .68 [.25] m, healthy = .33 [.16] m, Cohen d = 1.67 [0.81 to 2.52]). CONCLUSION: Individuals following ACLR demonstrate greater visual error during settings of high or low visual stimuli compared with healthy individuals to maintain single-limb postural stability. This population may rely on visual input to compensate for the somatosensory changes following injury.

Test-Retest Reliability and the Effects of Exercise on the King-Devick Test.

OBJECTIVE: To determine the test-retest reliability and the influence of exercise on King-Devick (K-D) test performance. DESIGN: Crossover study design. SETTING: Controlled laboratory. PARTICIPANTS: Participants consisted of 63 (39 women and 24 men) healthy, recreationally active college students who were 21.0 + 1.5 years of age. INDEPENDENT VARIABLES: Participants completed the K-D test using a 2-week, test-retest interval. The K-D test was administered before and after a counterbalanced exercise or rest intervention. Reliability was assessed using testing visits (visit 1 and visit 2) as the independent variables. Exercise or rest and time (baseline, postintervention) were used as independent variables to examine the influence of exercise. MAIN OUTCOME MEASURES: Intraclass correlation (ICC) coefficients with 95% confidence intervals were calculated between visits to assess reliability of K-D test completion time. A repeated-measure 2 x 2 analysis of variance (intervention × time) with post hoc paired t tests was used to assess the influence of exercise on K-D test performance. RESULTS: The K-D test was observed to have strong test-retest reliability [ICC2,1 = 0.90 (0.71, 0.96)] over time. No significant intervention-by-time interaction (P = 0.55) or intervention main effects (P = 0.68) on K-D time were observed. Mean differences of -1.5 and -1.7 seconds (P < 0.001) were observed between baseline and rest and exercise interventions for K-D test performance, respectively. Up to 32% (20/63) of participants were observed to have a false-positive K-D test performance before and after each intervention. CONCLUSIONS: Although strong test-retest reliability coefficients were observed using clinically relevant time points, a high false-positive rate warrants caution when interpreting the K-D test.

Foot impairments contribute to functional limitation in individuals with ankle sprain and chronic ankle instability.

PURPOSE: To investigate the clinical measures of foot posture and morphology, multisegmented joint motion and play, strength, and dynamic balance in recreationally active young adults with and without a history of a lateral ankle sprain (LAS), copers, and chronic ankle instability (CAI). METHODS: Eighty recreationally active individuals (healthy: n = 22, coper: n = 21, LAS: n = 17, CAI: n = 20) were included. Foot posture index (FPI), morphologic measures, joint motion (weight-bearing dorsiflexion (WBDF), rearfoot dorsiflexion, plantar flexion, inversion, eversion; forefoot inversion, eversion; hallux flexion, extension), joint play (proximal and distal tibiofibular; talocrural and subtalar, forefoot; 1st tarsometatarsal and metatarsophalangeal), strength (dorsiflexion, plantar flexion, inversion, eversion, hallux flexion, lesser toe flexion), and Star Excursion Balance Test (SEBT) (anterior, posteromedial, posterolateral) were assessed. RESULTS: There were no group differences in FPI or morphological measures. LAS and CAI groups had decreased ankle dorsiflexion (p = 0.001) and greater frontal plane motion (p < 0.001), first MT plantar flexion, and sagittal excursion (p < 0.001); increased talocrural glide (p = 0.02) and internal rotation (p < 0.001) and decreased forefoot inversion joint play (p < 0.001); and decreased strength in all measures (p < 0.001) except dorsiflexion compared to healthy controls. The LAS group also demonstrated decreased distal tibiofibular (p = 0.04) and forefoot general laxity (p = 0.05) and SEBT performance (anterior: p = 0.02; posteromedial: p < 0.001; posterolateral: p < 0.001). CONCLUSION: Individuals with LAS or CAI have increased pain, impaired physiologic and accessory joint motion, ligamentous tenderness, and strength in the foot and ankle. Clinicians should assess the multiple segments of the ankle-foot complex when caring for individuals with an LAS or CAI. LEVEL OF EVIDENCE: II.

Patient-Reported Outcomes and Perceived Confidence Measures in Athletes With a History of Ankle Sprain.

CONTEXT: Patient-reported outcome measures (PROs) and functional performance tests are recommended in the National Athletic Trainers' Association's position statement on the prevention and management of ankle sprains during the return-to-play process. Evaluating perceived confidence may be another valuable method to evaluate an athlete's readiness to return-to-play following an ankle sprain. OBJECTIVE: To evaluate the relationship between PROs and perceived confidence when performing functional performance tasks in high school athletes with a history of ankle sprain. DESIGN: Descriptive study. SETTING: Public high school. PATIENTS OR OTHER PARTICIPANTS: A total of 25 high school student-athletes (6 males and 19 females, age 16.2 [1.1] y, height 169.3 [7.7] cm, mass 63.2 [9.8] kg). INTERVENTION(S): None. MAIN OUTCOME MEASURES: The Cumberland Ankle Instability Tool, visual analog scale (VAS) for pain, Identification of Functional Ankle Instability, and Tampa Scale of Kinesiophobia-11 were completed by all participants. Participants then completed the weight-bearing lunge test; star excursion balance test; lateral, up-down, and triple hop tests; the single-leg vertical jump; and Southeast Missouri agility test and were asked to report their confidence in completing each task using a VAS with anchors of "no confidence" and "complete confidence." Pearson r correlations were calculated between the PROs and the confidence VAS scores of the functional tests. RESULTS: Moderate to strong negative correlations were identified between pain VAS measures and confidence VAS measures for all functional tests except the star excursion balance test and vertical jump. Moderate negative correlations were found between Tampa Scale of Kinesiophobia-11 scores and perceived confidence during the star excursion balance test and vertical jump. Finally, a moderate positive correlation was identified between Cumberland Ankle Instability Tool scores and perceived confidence measures during the Southeast Missouri agility test. CONCLUSIONS: High school athletes with a history of ankle sprain demonstrated significant correlations between several PROs and perceived confidence during various functional performance tests. The value of perceived confidence measures when making return-to-play decisions after ankle sprains warrants further investigation.

Single-Leg Jump Performance Before and After Exercise in Healthy and Anterior Cruciate Ligament Reconstructed Individuals.

CONTEXT: Many clinicians measure lower-extremity symmetry after anterior cruciate ligament reconstruction (ACLR); however, testing is completed in a rested state rather than postexercise. Testing postexercise may better model conditions under which injury occurs. OBJECTIVE: To compare changes in single-leg performance in healthy and individuals with history of ACLR before and after exercise. DESIGN: Repeated-measures case-control. SETTING: Laboratory. PATIENTS: Fifty-two subjects (25 control and 27 ACLR). INTERVENTION: Thirty minutes of exercise. MAIN OUTCOME MEASURES: Limb symmetry and involved limb performance (nondominant for healthy) for single-leg hop, ground contact time, and jump height during the 4-jump test. Cohen d effect sizes were calculated for all differences identified using a repeated-measures analysis of variance. RESULTS: Healthy controls hopped farther than ACLR before (d = 0.65; confidence interval [CI], 0.09 to 1.20) and after exercise (d = 0.60; CI, 0.04 to 1.15). Those with ACLR had longer ground contact time on the reconstructed limb compared with the uninvolved limb after exercise (d = 0.53; CI, -0.02 to 1.09), and the reconstructed limb had greater ground contact time compared with the healthy control limb after exercise (d = 0.38; CI, -0.21 to 0.73). ACLR were less symmetrical than healthy before (d = 0.38; CI, 0.17 to 0.93) and after exercise (d = 0.84; CI, 0.28 to 1.41), and the reconstructed limb demonstrated decreased jump height compared with the healthy control limbs before (d = 0.75; CI, 0.19 to 1.31) and after exercise (d = 0.79; CI, 0.23 to 1.36). CONCLUSIONS: ACLR became more symmetric, which may be from adaptations of the reconstructed limb after exercise. Changes in performance and symmetry may provide additional information regarding adaptations to exercise after reconstruction.

Walking Gait Mechanics and Gaze Fixation in Individuals With Chronic Ankle Instability.

CONTEXT: Many individuals who suffer a lateral ankle sprain will develop chronic ankle instability (CAI). Individuals with CAI demonstrate kinematic differences in walking gait, as well as somatosensory alterations compared with healthy individuals. However, the role of vision during walking gait in this population remains unclear. OBJECTIVE: To evaluate ankle kinematics, gaze deviations, and gaze velocity between participants with CAI and healthy controls while walking on a treadmill during 3 separate visual conditions (no target, fixed target, and moving target). DESIGN: Case-control study. SETTING: Laboratory. Patients (or Other Participants): Ten CAI participants and 10 healthy matched controls participated. MAIN OUTCOME MEASURES: Ankle sagittal and frontal plane kinematics were analyzed for the entire gait cycle. Average and standard deviation (SD) for gaze deviation and gaze velocity were calculated in the horizontal (X) and vertical (Y) planes. RESULTS: No significant differences were found between groups for either ankle kinematics or gaze variables; however, large effect sizes were found in the no target condition for average deviation of X (healthy 0.05 [0.02], CAI 0.12 [0.11]). Moderate effect sizes were identified in the no target condition for SD of Y (healthy 0.04 [0.03], CAI 0.11 [0.15]) and the moving target condition for average velocity of X (healthy 1.56 [0.73], CAI 2.27 [1.15]) and Y (healthy 1.07 [0.51], CAI 1.47 [0.52]). CONCLUSIONS: Although no significant differences were found between groups, it is possible that the role of vision in individuals with CAI may be altered with a more difficult task.

Landing Stiffness Between Individuals With and Without a History of Low Back Pain.

CONTEXT: Reduced spinal stabilization, delayed onset of muscle activation, and increased knee joint stiffness have been reported in individuals with a history of low back pain (LBP). Biomechanical adaptations resulting from LBP may increase the risk for future injury due to suboptimal loading of the lower-extremity or lumbar spine. Assessing landing mechanics in these individuals could help identify which structures might be susceptible to future injury. OBJECTIVE: To compare vertical and joint stiffness of the lower-extremity and lumbar spine between individuals with and without a previous history of LBP. DESIGN: Cross-sectional study. SETTING: Research laboratory. PARTICIPANTS: There were 45 participants (24 without a previous history of LBP-age 23 [8] y, height 169.0 [8.5] cm, mass 69.8 [13.8] kg; 21 with a previous history of LBP-age 25[9] y, height 170.0 [8.0] cm, mass 70.2 [11.8] kg). INTERVENTIONS: Single-limb landing trials on the dominant and nondominant limb from a 30-cm box. MAIN OUTCOME MEASURES: Vertical stiffness and joint stiffness of the ankle, knee, hip, and lumbar spine. RESULTS: Individuals with a previous history of LBP had lower vertical stiffness (P = .04), but not joint stiffness measures compared with those without a previous history of LBP (P > .05). Overall females had lower vertical (P = .01), ankle (P = .02), and hip stiffness (P = .04) compared with males among all participants. Males with a previous history of LBP had lower vertical stiffness compared with males without a previous history LBP (P = .01). Among all individuals without a previous history of LBP, females had lower vertical (P < .01) and ankle stiffness measures (P = .04) compared with males. CONCLUSIONS: Landing stiffness may differ among males and females and a previous history of LBP. Comparisons between individuals with and without previous LBP should be considered when assessing landing strategies, and future research should focus on how LBP impacts landing mechanics.

Improvements in Lower-Extremity Function Following a Rehabilitation Program With Patterned Electrical Neuromuscular Stimulation in Females With Patellofemoral Pain: A Randomized Controlled Trial.

CONTEXT: Patellofemoral pain (PFP) is a challenging condition, with altered kinematics and muscle activity as 2 common impairments. Single applications of patterned electrical neuromuscular stimulation (PENS) have improved both kinematics and muscle activity in females with PFP; however, the use of PENS in conjunction with a rehabilitation program has not been evaluated. OBJECTIVE: To determine the effects of a 4-week rehabilitation program with PENS on lower-extremity biomechanics and electromyography (EMG) during a single-leg squat (SLS) and a step-down task (SDT) in individuals with PFP. STUDY DESIGN: Double-blinded randomized controlled trial. SETTING: Laboratory. Patients of Other Participants: Sixteen females with PFP (age 23.3 [4.9] y, mass 66.3 [13.5] kg, height 166.1 [5.9] cm). INTERVENTION: Patients completed a 4-week supervised rehabilitation program with or without PENS. MAIN OUTCOME MEASURES: Curve analyses for lower-extremity kinematics and EMG activity (gluteus maximus, gluteus medius, vastus medialis oblique, vastus lateralis, biceps femoris, and adductor longus) were constructed by plotting group means and 90% confidence intervals throughout 100% of each task, before and after the rehabilitation program. Mean differences (MDs) and SDs were calculated where statistical differences were identified. RESULTS: No differences at baseline in lower-extremity kinematics or EMG were found between groups. Following rehabilitation, the PENS group had significant reduction in hip adduction between 29% and 47% of the SLS (MD = 4.62° [3.85°]) and between 43% and 69% of the SDT (MD = 6.55° [0.77°]). Throughout the entire SDT, there was a decrease in trunk flexion in the PENS group (MD = 10.91° [1.73°]). A significant decrease in gluteus medius activity was seen during both the SLS (MD = 2.77 [3.58]) and SDT (MD = 4.36 [5.38]), and gluteus maximus during the SLS (MD = 1.49 [1.46]). No differences were seen in the Sham group lower-extremity kinematics for either task. CONCLUSION: Rehabilitation with PENS improved kinematics in both tasks and decreased EMG activity. This suggests that rehabilitation with PENS may improve muscle function during functional tasks.

Effects of a 4-Week Intrinsic Foot Muscle Exercise Program on Motor Function: A Preliminary Randomized Control Trial.

Context: Intrinsic foot muscle (IFM) exercises are utilized clinically in the treatment of foot and ankle conditions. However, the effectiveness of training on IFM motor function is unknown. Objective: To study the effects of a 4-week IFM exercise program on motor function, perceived difficulty, and IFM motor activation measured using ultrasound imaging (USI) during 3 IFM exercises. Design: Single-blinded randomized control trial. Setting: Laboratory. Participants: A total of 24 healthy, recreationally active young adults without history of ankle-foot injury who have never performed IFM exercises participated (12 males and 12 females; mean age = 21.5 [4.8] y; body mass index = 23.5 [2.9] kg/m2) Intervention: Following randomization, participants allocated to the intervention group received a 4-week progressive home IFM exercise program performed daily. Participants in the control group did not receive any intervention. Main Outcome Measures: Clinician-assessed motor performance (4-point scale: 0 = does not initiate movement and 3 = performs exercise in standard pattern), participant-perceived difficulty (5-point Likert scale: 1 = very easy and 5 = very difficult), and USI motor activation measures (contracted measurementresting measurement) of the abductor hallucis, flexor digitorum brevis, quadratus plantae, and flexor hallucis brevis were assessed during toe-spread-out, hallux-extension, and lesser-toe-extension exercises. Results: The intervention group demonstrated significant improvement in motor performance in the toe-spread-out exercise (pre = 1.9 [0.5], post = 2.6 [0.5], P = .008) and less perceived difficulty in the toe-spread-out (pre = 3.1 [1.3], post = 2.3 [1.2], P = .01), hallux-extension (pre = 3.2 [1.5], post = 2.0 [1.2], P = .005), and lesser-toe-extension (pre = 1.9 [0.7], post = 1.2 [0.4], P = .03) exercises. Both groups demonstrated increased USI motor activation in the abductor hallucis during the toe-spread-out exercise (intervention: pre = 1.07 [0.06], post = 1.11 [0.08] and control: pre = 1.08 [0.06], post = 1.11 [0.06]; P = .05). No other significant main effects or group by time interactions were observed. Conclusion: A 4-week IFM exercise intervention resulted in improved motor performance and decreased perceived difficulty when performing the exercises, but not changes in USI measures of IFM activation compared with a control group.

Effect of Sex and Level of Activity on Lower-Extremity Strength, Functional Performance, and Limb Symmetry.

Context: Strength, functional performance, and limb symmetry are common objective clinical assessments used by clinicians to guide safe return to physical activity following injury. Population-specific unilateral limb outcomes or estimates of limb symmetry of these assessments should be established. Objective: To compare lower-extremity strength, functional performance, and limb symmetry in healthy participants based on sex and level of activity. Design: Descriptive laboratory study. Setting: Laboratory. Participants: A total of 117 healthy participants (72 males and 45 females; mass = 73.67 [13.60] kg, height = 1.76 [0.12] m, and age = 21.44 [2.92] y) without history of injury within 6 months were included. Interventions: Participants completed isokinetic concentric and isometric knee extension and flexion strength tasks at 90°/s, 180°/s, and 90°, respectively, and 4 hop tasks (single, cross-over, triple, and 6-m timed) during 1 session. Groups were separated by sex (male and female) and activity level (athlete and nonathlete). Participants rostered on National Collegiate Athletic Association (NCAA) Division I (DI) teams were considered as athletes, and non-NCAA DI healthy, uninjured participants were considered as nonathletes. Main Outcome Measures: Limb symmetry index (LSI), maximal voluntary isometric contraction (N·m/kg), peak torque (N·m/kg), average power (N·m/s), distance (m), and time hopped (s) were assessed. LSI was calculated by dividing the lower limb outcome by the higher limb outcome of the nondominant or dominant limb. Group differences were assessed through Mann-Whitney U tests and Cohen's d effect sizes for all comparisons. Results: LSI differences did not exist between groups. Mean LSIs for all participants ranged between 83.52% (12.54%) and 96.16% (3.82%). On average, males were stronger (range: d = 0.63-1.54), hopped farther (range: d = 1.52-1.63), and hopped faster (range: d = 1.67-1.68) than females. On average, some strength differences existed between athletes and nonathletes, but athletes hopped farther (range: d = 0.71-0.82) and faster (range: d = 0.87-0.88) than nonathletes. Conclusions: Unilateral limb strength and functional performance outcomes differ between sex and activity level, but not limb symmetry. These differences may be important for a clinician's understanding of normative values of common return-to-play assessment tasks.

Quadriceps and Patient-Reported Function in ACL-Reconstructed Patients: A Principal Component Analysis.

CONTEXT: Assessment of physical function for individuals after anterior cruciate ligament reconstruction (ACL-R) is complex and warrants the use of diverse evaluation strategies. To maximize the efficiency of assessment, there is a need to identify tests that provide the most meaningful information about this population. OBJECTIVE: To investigate underlying constructs of quadriceps muscle function that uniquely describe aspects of performance in patients after ACL-R and establish clinical thresholds for measures able to classify patients with and without ACL-R. DESIGN: Cross-sectional. SETTING: Research laboratory. Patients (or Other Participants): Seventy-two patients with a primary, unilateral ACL-R (32 males and 40 females, age = 26.0 [9.3] y, time since surgery = 46.5 [58.0] mo) and 30 healthy controls (12 males and 18 females, age = 22.7 [4.6] y). INTERVENTION(S): Quadriceps function was assessed bilaterally during 1 study visit. MAIN OUTCOME MEASURES: Isokinetic strength (peak torque, total work, and average power) at 90° and 180°/s, maximal voluntary isometric contraction torque, fatigue index, central activation ratio, Hoffmann reflex, and active motor threshold. Principal component analyses were performed for the involved limb, contralateral limb, and limb symmetry. Receiver-operator characteristic curve analyses were conducted to determine the diagnostic utility of each variable. Binary logistic regression was used to predict group membership (ACL-R vs healthy). RESULTS: Three components of peripheral, central, and combined (peripheral and central) muscle function were identified, explaining 70.7% to 80.5% of variance among measures of quadriceps function. Total knee-extensor work at 90°/s (≥18.4 J/kg), active motor threshold (≥39.5%), and central activation ratio (≥94.7%) of the involved limb were strong predictors of patient status and correctly classified 83.5% of patients with ACL-R (P < .001). CONCLUSIONS: Unique constructs of peripheral, central, and combined muscle function exist in patients with ACL-R. Total knee-extensor work at 90°/s, active motor threshold, and central activation ratio consistently explained a significant portion of variance in measures of quadriceps function, demonstrated acceptable to excellent diagnostic utility, and predicted group membership with 72.8% to 83.5% accuracy.

Effect of Impairment-Based Rehabilitation on Lower Leg Muscle Volumes and Strength in Patients With Chronic Ankle Instability: A Preliminary Study.

Context: Patients with chronic ankle instability (CAI) have demonstrated atrophy of foot and ankle musculature and deficits in ankle strength. The effect of rehabilitation on muscle morphology and ankle strength has not previously been investigated in patients with CAI. Objective: Our objective was to analyze the effect of impairment-based rehabilitation on intrinsic and extrinsic foot and ankle muscle volumes and strength in patients with CAI. Design: Controlled laboratory study. Setting: Laboratory. Patients: Five young adults with CAI. Intervention: Twelve sessions of supervised impairment-based rehabilitation that included range of motion, strength, balance, and functional exercises. Main Outcome Measures: Measures of extrinsic and intrinsic foot muscle volume and ankle strength measured before and after 4 weeks of supervised rehabilitation. Novel fast-acquisition magnetic resonance imaging was used to scan from above the femoral condyles through the entire foot. The perimeter of each muscle was outlined on each axial slice and then the 2-dimensional area was multiplied by the slice thickness (5 mm) to calculate muscle volume. Plantar flexion, dorsiflexion, inversion, and eversion isometric strength were measured using a hand-held dynamometer. Results: Rehabilitation resulted in hypertrophy of all extrinsic foot muscles except for the flexor hallucis longus and peroneals. Large improvements were seen in inversion, eversion, and plantar flexion strength following rehabilitation. Effect sizes for significant differences following rehabilitation were all large and ranged from 1.54 to 3.35. No significant differences were identified for intrinsic foot muscle volumes. Conclusion: Preliminary results suggest that impairment-based rehabilitation for CAI can induce hypertrophy of extrinsic foot and ankle musculature with corresponding increases in ankle strength.

Clinical Tests Have Limited Predictive Value for Chronic Ankle Instability When Conducted in the Acute Phase of a First-Time Lateral Ankle Sprain Injury.

OBJECTIVE: To evaluate whether a battery of clinical assessments for acute lateral ankle sprain (LAS) can be used to predict long-term recovery. DESIGN: Cohort study. SETTING: University biomechanics laboratory. PARTICIPANTS: Individuals (N=82) were assessed using a clinical test battery within 2 weeks of incurring a first-time LAS. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: The clinical test battery included scores on the talar glide test (degrees), the anterior drawer, talar tilt, figure of 8 for swelling (millimeters) and knee to wall (millimeters) tests, and handheld goniometric range of motion (inversion, eversion, and plantarflexion [in degrees]). Scores on the Cumberland Ankle Instability Tool taken 12 months after the clinical test battery were used to classify participants as having chronic ankle instability (CAI) or as being LAS copers. RESULTS: Forty percent of participants were designated as having CAI, with 60% being designated as LAS copers. A logistic regression analysis revealed that a combined model using scores from the talar glide, talar tilt, and anterior drawer tests in addition to plantarflexion range of motion was statistically significant (P<.01) and correctly classified cases with moderate accuracy (68.8%). The final model had moderate sensitivity (64%) and good specificity (72%). CONCLUSIONS: The clinical tests used in this investigation have limited predictive value for CAI when conducted in the acute phase of a first-time LAS injury.