Cognitive Training Improves Joint Stiffness Regulation and Function in ACLR Patients Compared to Healthy Controls.

As cognitive function is critical for muscle coordination, cognitive training may also improve neuromuscular control strategy and knee function following an anterior cruciate ligament reconstruction (ACLR). The purpose of this case-control study was to examine the effects of cognitive training on joint stiffness regulation in response to negative visual stimuli and knee function following ACLR. A total of 20 ACLR patients and 20 healthy controls received four weeks of online cognitive training. Executive function, joint stiffness in response to emotionally evocative visual stimuli (neutral, fearful, knee injury related), and knee function outcomes before and after the intervention were compared. Both groups improved executive function following the intervention (p = 0.005). The ACLR group had greater mid-range stiffness in response to fearful (p = 0.024) and injury-related pictures (p = 0.017) than neutral contents before the intervention, while no post-intervention stiffness differences were observed among picture types. The ACLR group showed better single-legged hop for distance after cognitive training (p = 0.047), while the healthy group demonstrated no improvement. Cognitive training enhanced executive function, which may reduce joint stiffness dysregulation in response to emotionally arousing images and improve knee function in ACLR patients, presumably by facilitating neural processing necessary for neuromuscular control.

Concussion is not associated with elevated rates of lower-extremity musculoskeletal injuries in National Football League Players.

OBJECTIVE: Emerging evidence has identified an ~2x elevated risk of musculoskeletal (MSK) injury in the year following a concussion. Most of these studies have examined a single college/university athletic department and may lack generalizability to professional sports. Therefore, the purpose of this study was to assess the odds of post-concussion MSK injury utilizing publicly available National Football League (NFL) injury reports. METHODS: Concussions were identified through a review of published NFL injury reports during the 2015, 2016, and 2017 regular seasons. Concussed players were matched by team and position, and injuries were tracked for both groups for the remainder of the season. A chi-square analysis compared the frequency of MSK injury in both groups and a Cox Proportional Hazard model calculated the risk of sustaining a subsequent MSK injury. RESULTS: There were 322 concussed NFL players who met inclusion criteria and were successfully matched. From the time of concussion through the remainder of the season, 21.4% of the concussed players were injured and 26.4% of control participants were injured. There was no difference in MSK injury rates (p = 0.166), and the relative risk ratio was 0.90 for subsequent injury in the concussion group. There was no difference in the time to event for subsequent MSK between the two groups (p = 0.123). CONCLUSION: The primary finding of this study was no elevated risk of post-concussion MSK in NFL football players.

Identifying Range-of-Motion Deficits and Talocrural Joint Laxity After an Acute Lateral Ankle Sprain.

CONTEXT: Approximately 72% of patients with an ankle sprain report residual symptoms 6 to 18 months later. Although 44% of patients return to activity in less than 24 hours after experiencing a sprain, residual symptoms should be evaluated in the long term to determine if deficits exist. These residual symptoms may be due to the quality of ligament tissue and motion after injury. OBJECTIVE: To compare mechanical laxity of the talocrural joint and dorsiflexion range of motion (DFROM) over time (24 to 72 hours, 2 to 4 weeks, and 6 months) after an acute lateral ankle sprain (LAS). DESIGN: Cross-sectional study. SETTING: Athletic training research laboratory. PATIENTS OR OTHER PARTICIPANTS: A total of 108 volunteers were recruited. Fifty-five participants had an acute LAS and 53 participants were control individuals without a history of LAS. MAIN OUTCOME MEASURE(S): Mechanical laxity (talofibular interval and anterior talofibular ligament length) was measured in inversion (INV) and via the anterior drawer test. The weight-bearing lunge test was conducted and DFROM was measured. The data were analyzed using repeated-measures analysis of variance, independent-samples t tests, and 1-way analysis of variance. RESULTS: Of the 55 LASs, 21 (38%) were grade I, 27 (49%) were grade II, and 7 (13%) were grade III. Increases were noted in DFROM over time, between 24 and 72 hours, at 2 to 4 weeks, and at 6 months (P < .05). The DFROM was less in participants with grade III than grade I LASs (P = .004) at 24 to 72 hours; INV length was greater at 24 to 72 hours than at 2 to 4 weeks (P = .023) and at 6 months (P = .035) than at 24 to 72 hours. The anterior drawer length (P = .001) and INV talofibular interval (P = .004) were greater in the LAS group than in the control group at 6 months. CONCLUSIONS: Differences in range of motion and laxity were evident among grades at various time points and may indicate different clinical responses after an LAS.

Negative Emotion and Joint-Stiffness Regulation Strategies After Anterior Cruciate Ligament Injury.

CONTEXT: Fear of reinjury after an anterior cruciate ligament (ACL) reconstruction (ACLR) may be associated with persistent deficits in knee function and subsequent injury. However, the effects of negative emotion on neuromuscular-control strategies after an ACL injury have remained unclear. OBJECTIVE: To identify how negative emotional stimuli affect neural processing in the brain and muscle coordination in patients after anterior cruciate ligament reconstruction compared with healthy control participants. DESIGN: Case-control study. SETTING: Neuromechanics laboratory. PATIENTS OR OTHER PARTICIPANTS: Twenty patients after unilateral anterior cruciate ligament reconstruction and 20 healthy recruits. MAIN OUTCOME MEASURE(S): Electrocortical θ (4-8 Hz) activity (event-related synchronization, % increased power relative to a nonactive baseline) at selected electrodes placed at the frontal (F3, Fz, F4) and parietal (P3, Pz, P4) cortices using electroencephalography, neurophysiological cardiac changes (beats/min), and subjective fear perceptions were measured, along with joint stiffness (Nm/°/kg) with and without an acoustic stimulus in response to 3 types of emotionally evocative images (neutral, fearful, and knee-injury pictures). RESULTS: Both groups had greater frontoparietal θ power with fearful pictures (Fz: 35.9% ± 29.4%; Pz: 81.4% ± 66.8%) than neutral pictures (Fz: 24.8% ± 29.7%, P = .002; Pz: 64.2 ± 54.7%, P = .024). The control group had greater heart-rate deceleration with fearful (-4.6 ± 1.4 beats/min) than neutral (-3.6 ± 1.3 beats/min, P < .001) pictures, whereas the ACLR group exhibited decreased heart rates with both the fearful (-4.6 ± 1.3 beats/min) and injury-related (-4.4 ± 1.5 beats/min) pictures compared with neutral pictures (-3.4 ± 1.4 beats/min, P < .001). Furthermore, during the acoustic startle condition, fearful pictures increased joint stiffness (Nm/°/kg) in the ACLR group at the midrange (0°-20°: 0.027 ± 0.02) and long range (0°-40°: 0.050 ± 0.02) compared with the neutral pictures (0°-20°: 0.017 ± 0.01, P = .024; 0°-40°: 0.043 ± 0.02, P = .014). CONCLUSIONS: Negative visual stimuli simultaneously altered neural processing in the frontoparietal cortices and joint-stiffness regulation strategies in response to a sudden perturbation. The adverse effects of fear on neuromuscular control may indicate that psychological interventions should be incorporated in neuromuscular-control exercise programs after ACL injury.

Ankle Strength Deficits in a Cohort of College Athletes With Chronic Ankle Instability.

CONTEXT: Lateral ankle sprains commonly occur in an athletic population and can lead to chronic ankle instability. OBJECTIVE: To compare ankle strength measurements in athletes who have mechanical laxity and report functional instability after a history of unilateral ankle sprains. DESIGN: Retrospective cohort. SETTING: Athletic Training Research Lab. PARTICIPANTS: A total of 165 National Collegiate Athletic Association Division I athletes, 97 males and 68 females, with history of unilateral ankle sprains participated. MAIN OUTCOME MEASURES: Functional ankle instability was determined by Cumberland Ankle Instability Tool scores and mechanical ankle instability by the participant having both anterior and inversion/eversion laxity. Peak torque strength measures, concentric and eccentric, in 2 velocities were measured. RESULTS: Of the 165 participants, 24 subjects had both anterior and inversion/eversion laxity and 74 self-reported functional ankle instability on their injured ankle. The mechanical ankle instability group presented with significantly lower plantar flexion concentric strength at 30°/s (139.7 [43.7] N·m) (P = .01) and eversion concentric strength at 120°/s (14.8 [5.3] N·m) (P = .03) than the contralateral, uninjured ankle (166.3 [56.8] N·m, 17.4 [6.2] N·m, respectively). CONCLUSION: College athletes who present with mechanical laxity on a previously injured ankle exhibit plantar flexion and eversion strength deficits between ankles.

Neuroplastic changes in anterior cruciate ligament reconstruction patients from neuromechanical decoupling.

The purpose of this study was to identify how the brain simultaneously perceives proprioceptive input during joint loading in anterior cruciate ligament reconstruction (ACLR) patients, when compared to healthy controls. Seventeen ACLR patients (ACLR) and seventeen controls (CONT) were tested for the somatosensory cortical activation using electroencephalography (EEG) while measuring knee laxity using a knee arthrometer. The relationship between cortical activation and joint laxity within group was also examined. The ACLR patients had increased cortical activation (36.4% ± 11.5%) in the somatosensory cortex during early loading (ERD1) to the injured limb compared to the CONT's matched limb (25.3% ± 13.2%, P = 0.013) as well as compared to the noninjured limb (25.1% ± 14.2%, P = 0.001). Higher somatosensory cortical activity during midloading (ERD2) to the ACLR knee positively correlated with knee laxity (mm) during early loading (LAX1, r = 0.530), midloading (LAX2, r = 0.506), total anterior loading (LAXA, r = 0.543), and total antero-posterior loading (LAXT, r = 0.501), while the noninjured limb revealed negative correlations between ERD1 and LAXA (r = -0.534) as well as between ERD2 and LAX2 (r = -0.565). ACLR patients demonstrate greater brain activation during joint loading in the injured knees when compared to healthy controls' matched knees as well as contralateral healthy knees, while the CONT group shows similar brain activation patterns during joint loading between limbs. These different neural activation strategies may indicate neuromechanical decoupling following an ACL reconstruction and evidence of altered sensorimotor perception and control of the knee (neuroplasticity), which may be critical to address after surgery for optimal neuromuscular control and patients' outcomes.

Evaluating Postural Control and Ankle Laxity Between Taping and High-Top Cleats in High School Football Players.

CONTEXT: Lateral ankle sprains are the most common injuries in high school sports. While ankle taping is a preferred method of external prophylactic support, its restrictive properties decline during exercise. The Under Armour® Highlight cleat is marketed on the premise that it provides added support without the need for additional ankle taping. OBJECTIVE: To determine if differences in ankle joint laxity and postural control exist between football players wearing the Under Armour® Highlight cleat (Under Armour Inc, Baltimore, MD) as compared to a low/mid-top cleat with ankle tape. DESIGN: Crossover trial. SETTING: Athletic training room and football practice field sideline. PATIENTS: 32 interscholastic football players (15.8 ± 1.0 y; 178.9 ± 7.4 cm; 87.1 ± 21.4 kg). INTERVENTIONS: Ankle laxity was assessed using an instrumented ankle arthrometer (Blue Bay Research Inc, Milton, FL), while postural control testing was performed on the Tekscan MobileMat™ Balanced Error Scoring System (BESS; South Boston, MA). The 2 treatments included Under Armour® Highlight cleats and a low/mid-top cleat with ankle tape applied to the nondominant ankle only. Measurements were taken before and immediately after practice. MAIN OUTCOME MEASURES: The independent variable was treatment (Highlight vs low/mid-top cleat with ankle tape). Dependent variables included ankle arthrometry measures of anterior displacement (mm), inversion/eversion rotation (deg), and the modified BESS error scores. A linear mixed-effects model was used for analysis. RESULTS: The low/mid-top cleat with tape condition had significantly higher inversion range-of-motion (ROM) and inversion/eversion rotation postexercise when compared to the Highlight cleat (P < 0.05). CONCLUSIONS: The results of this study provide some evidence that the Under Armour® Highlight cleat restricts ankle ROM following a training session better than the taped low/mid-top cleat. Further study is warranted to determine if this high-top style of football cleat can reduce the incidence of ankle sprains and how it might compare to spat taping.

The Effect of Shoulder Plyometric Training on Amortization Time and Upper-Extremity Kinematics.

CONTEXT: Plyometric training is credited with providing benefits in performance and dynamic restraint. However, limited prospective data exist quantifying kinematic adaptations such as amortization time, glenohumeral rotation, and scapulothoracic position, which may underlie the efficacy of plyometric training for upper-extremity rehabilitation or performance enhancement. OBJECTIVE: To measure upper-extremity kinematics and plyometric phase times before and after an 8-wk upper-extremity strength- and plyometric-training program. DESIGN: Randomized pretest-posttest design. SETTING: Research laboratory. PARTICIPANTS: 40 recreationally active men (plyometric group, age 20.43 ± 1.40 y, height 180.00 ± 8.80 cm, weight 73.07 ± 7.21 kg; strength group, age 21.95 ± 3.40 y, height 173.98 ± 11.91 cm, weight 74.79 ± 13.55 kg). INTERVENTION: Participants were randomly assigned to either a strength-training group or a strength- and plyometric-training group. Each participant performed the assigned training for 8 wk. MAIN OUTCOME MEASURES: Dynamic and static glenohumeral and scapular-rotation measurements were taken before and after the training programs. Dynamic measurement of scapular rotation and time spent in each plyometric phase (concentric, eccentric, and amortization) during a ball-toss exercise were recorded while the subjects were fitted with an electromagnetic tracking system. Static measures included scapular upward rotation at 3 different glenohumeral-abduction angles, glenohumeral internal rotation, and glenohumeral external rotation. RESULTS: Posttesting showed that both groups significantly decreased the time spent in the amortization, concentric, and eccentric phases of a ball-toss exercise (P < .01). Both groups also exhibited significantly decreased static external rotation and increased dynamic scapular upward rotation after the training period (P < .01). The only difference between the training protocols was that the plyometric-training group exhibited an increase in internal rotation that was not present in the strength-training group (P < .01). CONCLUSION: These findings support the use of both upper-extremity plyometrics and strength training for reducing commonly identified upper-extremity-injury risk factors and improving upper-extremity performance.

Assessing performance, stability, and cleat comfort/support in collegiate club soccer players using prophylactic ankle taping and bracing.

Soccer athletes at all levels of play are keenly aware of their equipment needs including cleat wear, and want to be protected from injury but without impeding on-field performance. Ankle injury is a common disorder that is prevalent in the sport of soccer and recent improvements in ankle prophylaxis interventions have proven effective. The aim of this study was to determine if the use of elastic taping or a neoprene sleeve alters performance, stability, and cleat comfort/support in soccer players compared to wearing a soccer cleat without any external support. Twenty male collegiate club soccer players were recruited and randomly assigned to the three conditions (untaped control, taped, neoprene sleeve). Performance testing and comfort/support assessment for each condition took place in one on-field test session, while stability testing was completed during a separate laboratory session. The only significant finding was improved inversion/eversion stability in both the tape and sleeve conditions as compared to the cleated condition. The addition of tape or a sleeve did not have an adverse effect on performance or comfort during functional and stability testing, and should therefore be considered as a method to decrease ankle injuries in soccer athletes as external supports provide increased stability in inversion/eversion range of motion.

Examining Ankle-Joint Laxity Using 2 Knee Positions and With Simulated Muscle Guarding.

CONTEXT: Several factors affect the reliability of the anterior drawer and talar tilt tests, including the individual clinician's experience and skill, ankle and knee positioning, and muscle guarding. OBJECTIVES: To compare gastrocnemius activity during the measurement of ankle-complex motion at different knee positions, and secondarily, to compare ankle-complex motion during a simulated trial of muscle guarding. DESIGN: Cross-sectional study. SETTING: Research laboratory. PATIENTS OR OTHER PARTICIPANTS: Thirty-three participants aged 20.2 ± 1.7 years were tested. INTERVENTION(S): The ankle was loaded under 2 test conditions (relaxed, simulated muscle guarding) at 2 knee positions (0°, 90° of flexion) while gastrocnemius electromyography (EMG) activity was recorded. MAIN OUTCOME MEASURE(S): Anterior displacement (mm), inversion-eversion motion (°), and peak EMG amplitude values of the gastrocnemius (µV). RESULTS: Anterior displacement did not differ between the positions of 0° and 90° of knee flexion (P = .193). Inversion-eversion motion was greater at 0° of knee flexion compared with 90° (P < .001). Additionally, peak EMG amplitude of the gastrocnemius was not different between 0° and 90° of knee flexion during anterior displacement (P = .101). As expected, the simulated muscle-guarding trial reduced anterior displacement compared with the relaxed condition (0° of knee flexion, P = .008; 90° of knee flexion, P = .016) and reduced inversion-eversion motion (0° of knee flexion, P = .03; 90° of knee flexion, P < .001). CONCLUSIONS: In a relaxed state, the gastrocnemius muscle did not appear to affect anterior ankle laxity at the 2 most common knee positions for anterior drawer testing; however, talar tilt testing may be best performed with the knee in 0° of knee flexion. Finally, our outcomes from the simulated muscle-guarding condition suggest that clinicians should use caution and be aware of reduced perceived laxity when performing these clinical examination techniques immediately postinjury.

Brains and Sprains: The Brain's Role in Noncontact Anterior Cruciate Ligament Injuries.

Small mental errors in judgment or coordination at illtimed phases of movement planning could lead to the rapid, premature onset of large joint forces during sports. If these loads are not fully anticipated, then preprogrammed muscle contractions may be insufficient for stiffness levels to provide dynamic restraint, regardless of sex. This sequence of events would limit the capacity of muscles to act in a load-compensating manner, thereby exposing capsuloligamentous structures to failure. The importance of various neuropsychological characteristics in injury proneness should be explored to enhance prevention and rehabilitation strategies.

Adaptations of the Shoulder to Overhead Throwing in Youth Athletes.

CONTEXT: The high number of repetitions and high forces associated with overhead throwing lead to anatomical adaptations, such as humeral retrotorsion and posterior-capsule thickness, in elite and professional baseball athletes. However, little is known about the origin and progression of these changes that may account for the increasing trend of chronic shoulder injuries in youth baseball and precipitate subsequent pathologic conditions throughout a young athlete's lifetime. OBJECTIVE: To investigate the relationship of age and upper extremity dominance on humeral retrotorsion, posterior-capsule thickness, and glenohumeral range of motion. DESIGN: Cross-sectional study. SETTING: Research laboratory, local baseball fields, and training facilities. PATIENTS OR OTHER PARTICIPANTS: Thirty-six boys (mean age = 10.94 ± 1.34 years, height = 151.31 ± 12.17 cm, mass = 42.51 ± 10.32 kg) ranging in age from 8 to 12 years and involved in organized youth baseball. MAIN OUTCOME MEASURE(S): Diagnostic ultrasound was used to determine humeral retrotorsion and posterior-capsule thickness. Glenohumeral internal rotation and external rotation were measured using a handheld inclinometer. We used 2 × 2 mixed-model analyses of variance to compare the influence of limb dominance and age on the dependent variables of humeral retrotorsion, posterior-capsule thickness, internal rotation, and external rotation. RESULTS: The dominant shoulders of youth throwers exhibited less glenohumeral internal rotation but greater humeral retrotorsion, posterior-capsule thickness, and glenohumeral external rotation than the nondominant shoulders. Dominant internal rotation was greater in the 8- to 10-year-old group than in the 11- to 12-year-old group, and results trended toward a difference (F1,33 = 4.12, P = .05). Correlations existed between humeral retrotorsion and range of motion (P < .05). CONCLUSIONS: The structural adaptations in the dominant shoulders of younger baseball players were similar to adaptations observed in older baseball athletes, indicating that more examination is needed in younger athletes. We are the first to demonstrate greater posterior-capsule thickness in the dominant shoulders of youth baseball athletes.

The use of shear thickening nanocomposites in impact resistant materials.

The work presented here demonstrates using a novel, field-responsive nanocomposite based on shear thickening fluids (STFs) as responsive protective materials with superior damping and energy adsorption properties. Peak forces and accelerations measured using an instrumented Instron drop tower demonstrate that STF nanocomposite prototypes and impact foam taken from a commercial football helmet have similar performance for low kinetic energy impacts. However, tests with STF nanocomposite samples exhibit significantly reduced peak acceleration and peak force for impacts above 15 J. Thus, the STF containing nanocomposite material provides improved energy adsorption upon impact as compared to the commercial foam. These tests suggest that STF nanocomposite materials have promising potential as novel energy dissipating components in personal protective equipment.

Individuals with medial knee osteoarthritis show neuromuscular adaptation when perturbed during walking despite functional and structural impairments.

Neuromuscular control relies on sensory feedback that influences responses to changing external demands, and the normal response is for movement and muscle activation patterns to adapt to repeated perturbations. People with knee osteoarthritis (OA) are known to have pain, quadriceps weakness, and neuromotor deficits that could affect adaption to external perturbations. The aim of this study was to analyze neuromotor adaptation during walking in people with knee OA (n = 38) and controls (n = 23). Disability, quadriceps strength, joint space width, malalignment, and proprioception were assessed. Kinematic and EMG data were collected during undisturbed walking and during perturbations that caused lateral translation of the foot at initial contact. Knee excursions and EMG magnitudes were analyzed. Subjects with OA walked with less knee motion and higher muscle activation and had greater pain, limitations in function, quadriceps weakness, and malalignment, but no difference was observed in proprioception. Both groups showed increased EMG and decreased knee motion in response to the first perturbation, followed by progressively decreased EMG activity and increased knee motion during midstance over the first five perturbations, but no group differences were observed. Over 30 trials, EMG levels returned to those of normal walking. The results illustrate that people with knee OA respond similarly to healthy individuals when exposed to challenging perturbations during functional weight-bearing activities despite structural, functional, and neuromotor impairments. Mechanisms underlying the adaptive response in people with knee OA need further study.

Differences in lateral drop jumps from an unknown height among individuals with functional ankle instability.

CONTEXT: Functional ankle instability (FAI) is a debilitating condition that has been reported to occur after 20% to 50% of all ankle sprains. Landing from a jump is one common mechanism of ankle injury, yet few researchers have explored the role of visual cues and anticipatory muscle contractions, which may influence ankle stability, in lateral jumping maneuvers. OBJECTIVE: To examine muscle-activation strategies between FAI and stable ankles under a lateral load and to evaluate the differences in muscle activation in participants with FAI and participants with stable ankles when they were unable to anticipate the onset of lateral loads during eyes-open versus eyes-closed conditions. DESIGN: Case-control study. SETTING: Controlled laboratory setting. PATIENTS OR OTHER PARTICIPANTS: A total of 40 people participated: 20 with FAI and 20 healthy, uninjured, sex- and age-matched persons (control group). INTERVENTION(S): Participants performed a 2-legged lateral jump off a platform onto a force plate set to heights of 35 cm or 50 cm and then immediately jumped for maximal height. They performed jumps in 2 conditions (eyes open, eyes closed) and were unaware of the jump height when their eyes were closed. MAIN OUTCOME MEASURE(S): Amplitude normalized electromyographic (EMG) area (%), peak (%), and time to peak in the tibialis anterior (TA), peroneus longus (PL), and lateral gastrocnemius (LG) muscles were measured. RESULTS: Regardless of the eyes-open or eyes-closed condition, participants with FAI had less preparatory TA (t158 = 2.22, P = .03) and PL (t158 = 2.09, P = .04) EMG area and TA (t158 = 2.45, P = .02) and PL (t158 = 2.17, P = .03) peak EMG than control-group participants. CONCLUSIONS: By removing visual cues, unanticipated lateral joint loads occurred simultaneously with decreased muscle activity, which may reduce dynamic restraint capabilities in persons with FAI. Regardless of visual impairment and jump height, participants with FAI exhibited PL and TA inhibition, which may limit talonavicular stability and intensify lateral joint surface compression and pain.

Assessment of subacromial space and its relationship with scapular upward rotation in college baseball players.

CONTEXT: Subacromial impingement is a common injury in baseball players and has been linked to a reduction in the subacromial space. In addition, it has been suggested that decreases in scapular upward rotation will lead to decreases in the subacromial space and ultimately impingement syndrome. OBJECTIVE: The objective of this study was to evaluate the relationship between acromiohumeral distance and scapular upward rotation in healthy college baseball players. DESIGN: Posttest-only study design. SETTING: Controlled laboratory setting. PARTICIPANTS: 24 healthy college baseball players. INTERVENTION: Participants were measured for all dependent variables at preseason. MAIN OUTCOME MEASURES: Acromiohumeral distance at rest and 90° of abduction was measured with a diagnostic ultrasound unit. Scapular upward rotation at rest and 90° of abduction was measured with a digital inclinometer. RESULTS: Dominant-arm acromiohumeral distance at rest and 90° of abduction (P = .694, P = .840) was not significantly different than in the nondominant arm. In addition, there was not a significant correlation between acromiohumeral distance and scapular upward rotation at rest and 90° of abduction for either the dominant or the nondominant arm. CONCLUSIONS: These results indicate that the acromiohumeral distance is not adapting in the dominant arm in healthy throwing athletes. In addition, a relationship was not identified between acromiohumeral distance and scapular upward rotation, which was previously suggested. These results may suggest that changes that are typically seen in an injured population may be occurring due to the injury and are not preexisting. In addition, scapular upward rotation may not be the only contributing factor to acromiohumeral distance.

Effect of elastic taping on postural control deficits in subjects with healthy ankles, copers, and individuals with functional ankle instability.

BACKGROUND: Ankle sprains are the most common injury among physically active people, with common sequelae including repeated episodes of giving way, termed functional ankle instability. Copers are a cohort in ankle research comprised of those who have sprained their ankle but have not suffered any further dysfunction. The use of an elastic tape, Kinesio Tape, in sports medicine practice has recently gained popularity and may help improve postural control deficits related to functional ankle instability. The purpose of this study was to examine the immediate and prolonged effects of Kinesio Taping on postural control in healthy, coper, and unstable ankles as measured through single-limb balance on a force plate. METHODS: Sixty physically active, college-aged participants (72.5 ± 9.7 cm, 74.2 ± 16.2 kg, 21.5 ± 2.6 years) were stratified into healthy, coper, or unstable groups using the Cumberland Ankle Instability Tool (CAIT) combined with their history of ankle injury. Dependent variables included time-to-boundary (TTB) measures and traditional center of pressure (COP) measures in both the mediolateral (frontal) and anteroposterior (sagittal) planes. Testing was performed prior to tape application, immediately after application of the tape, 24 hours following tape application, and immediately after tape removal. RESULTS: Significant differences between groups were observed for COP standard deviation and range in the sagittal plane. Significant differences between tape conditions for TTB absolute minima and standard deviation were also noted. Post hoc testing revealed large to medium effect sizes for the group differences and very small effect sizes for the differences between conditions. CONCLUSIONS: Our study did not reveal decisively relevant changes following application of Kinesio Tape to the ankle. However, we did observe sagittal plane postural control deficits in subjects with ankle instability measured through summary COP variables over 20-second trials. CLINICAL RELEVANCE: Ankle instability is a concern for many clinicians. Kinesio Taping, although a popular form of clinical intervention, remains understudied. Evidence from this study does not support the use of Kinesio Taping for improving postural control deficits in those with ankle instability.

Change in glenohumeral rotation and scapular position after a Division I collegiate baseball season.

CONTEXT: Pathologies such as anterior instability and impingement are common in baseball and have been linked to decreases in internal-rotation (IR) motion and concurrent increases in external-rotation (ER) motion. In addition, alterations to scapular upward rotation have been identified in this population. OBJECTIVE: To measure glenohumeral (GH) IR and ER rotation, total range of motion (ROM), and scapular upward rotation throughout the course of a Division I collegiate baseball season. DESIGN: Pretest to posttest study. SETTING: Controlled laboratory setting. PARTICIPANTS: Thirty-one collegiate baseball players with no current shoulder or elbow injury completed this study. INTERVENTION: Participants were measured for all dependent variables at preseason and postseason. MAIN OUTCOME MEASURES: GH IR and ER were measured supine with the scapula stabilized. Total GH ROM was calculated as the sum of IR and ER measures. Scapular upward rotation was tested at rest, 60°, 90°, and 120° of GH abduction in the scapular plane. RESULTS: Overall, the dominant arm had significantly less GH IR and significantly more ER than the nondominant arm. The total motion on the dominant arm was significantly less than on the nondominant arm. No significant differences were observed from preseason to postseason for IR, ER, or total motion. Dominant-arm scapular upward rotation significantly decreased at 60°, 90°, and 120° of abduction from preseason to postseason. CONCLUSION: Collegiate baseball players presented with significant GH-motion differences (decreases in IR and increases in ER) in their dominant arm compared with their nondominant arm. There was also significantly less total motion on the dominant arm. After 12 wk of competitive Division I collegiate baseball, there were significant decreases in upward rotation over the season.

Neuromuscular and stiffness adaptations in division I collegiate baseball players.

To compare bi-lateral shoulder EMG, active and short range glenohumeral stiffness, and examine its correlation to posterior capsule thickness (PCT) in collegiate baseball players. Surface and fine wire EMG was recorded on shoulder and scapular musculature during stiffness testing. Posterior capsule thickness was assessed separately using a diagnostic ultrasound. Serratus anterior EMG area and peak on the dominant arm was significantly greater compared to the non-dominant arm. The dominant arm had significantly greater active and short range glenohumeral stiffness compared to the non-dominant arm. Active glenohumeral stiffness was significantly correlated with PCT, however short range glenohumeral stiffness was not significantly correlated with PCT. Healthy collegiate baseball players present with adaptations of their stiffness regulation strategies. There were also correlations between stiffness and morphologic changes. Our results support the theory that PCT has an impact on the energy absorption capabilities of the shoulder during the deceleration phase of throwing. It also seems that tightening of the series elastic component within the posterior rotator cuff may be causing the increase in short range stiffness on the dominant arm.

Examining neuromuscular control during landings on a supinating platform in persons with and without ankle instability.

BACKGROUND: Ankle instability is a costly public health concern because of the associated recurrent sprains. It is evident there are neuromuscular control deficits predisposing these individuals to their ankle "giving way." Individuals with a history of lateral ankle sprain, who did not develop instability, may hold the key to understanding proper neuromuscular control after injury. HYPOTHESES: On the basis of previous research, the authors hypothesized that individuals with ankle instability would demonstrate reduced peroneal activation, causing a more inverted position of the ankle, before and after landing. STUDY DESIGN: Controlled laboratory study. METHODS: This study aimed to evaluate preparatory and reactive neuromuscular control when landing on a custom-designed ankle supinating device in individuals with ankle instability (AI), individuals with a history of lateral ankle sprains without instability (LAS), and uninjured controls (CON). Forty-five participants (15 per group) were asked to land on a device built to simulate the mechanism of a lateral ankle sprain (supination) while kinematics and muscle activity of the lower extremity were monitored. RESULTS: Contrary to our hypotheses, the AI group displayed significantly increased preparatory (P = .01) and reactive (P = .02) peroneal activation, while the LAS group demonstrated a trend toward increased preparatory tibialis anterior muscle activation (P = .07), leading to a decreased plantar flexion of the ankle at landing. CONCLUSION: The AI group was likely acting in a protective fashion to a potentially injurious situation, indicating these individuals can activate the peroneals if needed. The LAS group's strategy may be a safer strategy in that a less plantar-flexed position of the ankle is more close-packed and stable. Further, it appears the long-latency response of the peroneals may be enhanced in these individuals, which indicates motor learning at the supraspinal level to promote dynamic restraint. CLINICAL RELEVANCE: Individuals with AI can increase peroneal activation when necessary to dynamically stabilize the ankle, indicating the potential for training/rehabilitation. Further, the LAS group may deploy a different control strategy after injury to protect the ankle from subsequent sprains, which deserves investigation during activities of daily living. A greater understanding of these strategies will lead to the development of more appropriate treatment paradigms after injury to minimize the incidence of instability.