J. Craig Garrison

Gender Differences in Gluteus Medius Muscle Activity Exist in Soccer Players Performing a Forward Jump

The purpose of this study was to evaluate gender differences in muscle activity while landing from a forward jump. Eight male and 8 female division-one varsity soccer athletes participated in this study. Subjects performed five trials of a 100 cm forward jump single leg landing. Surface electromyography (EMG) was collected at the gluteus medius, vastus lateralis, lateral hamstring, and medial gastrocnemius. Data were interpreted by VICON workstation and analyzed with Acknowledge software. Average root mean square of 200 ms following initial heel contact from landing were normalized to static one-leg stance and used in data analysis. A fixed-effect multivariate analysis of variance showed average gluteus medius activity was significantly higher in males (7.16 ± 3.16) than in females (2.62 ± 0.95). There were no differences between genders for any of the other muscles collected. Gender-specific neuromuscular strategies used to attenuate the forces of landing may involve more gluteus medius muscle activity in males than in females.

Baseball Players Diagnosed With Ulnar Collateral Ligament Tears Demonstrate Decreased Balance Compared to Healthy Controls

STUDY DESIGN Cross-sectional. OBJECTIVES To compare lower extremity balance and shoulder range of motion in baseball players with ulnar collateral ligament (UCL) tears to a healthy cohort. Background Throwing is a complex motion that requires balance and coordination to effectively transfer energy through the kinetic chain. In theory, poorer balance could negatively affect throwing mechanics and lead to injury. METHODS Thirty baseball players (mean ± SD age, 18.5 ± 1.9 years) with a diagnosis of a UCL tear of their throwing arm were compared to 30 players (age, 19.0 ± 1.1 years) without a UCL tear. All participants were competing at either the high school or collegiate level and reported an average ± SD of 13.5 ± 1.7 years of playing experience. The Y Balance Test composite scores were calculated for the stance and lead lower extremities of all players. Shoulder range of motion was used to calculate glenohumeral internal rotation deficit and side-to-side differences in total rotational motion. Group comparisons were made between participants with and without UCL tears using independent t tests. RESULTS Baseball players with UCL tears scored significantly lower on the Y Balance Test for both the stance (P<.001) and lead (P<.001) lower extremities compared to the noninjured cohort. No between-group differences were noted in glenohumeral internal rotation deficit (P = .453), whereas the mean ± SD side-to-side difference in total rotational motion was -6.0° ± 9.6° for the injured group, compared to -0.4° ± 9.6° for the control group (P = .028). CONCLUSION Participants with a UCL tear demonstrated decreased performance for their stance and lead lower extremities during the Y Balance Test. These data are consistent with a clinical hypothesis of a potential association between impaired balance and UCL tears in high school and collegiate baseball players. The lower total rotational motion of the dominant shoulder in participants with UCL tears needs to be considered in the interpretation of those results.

Decreased Quadriceps Activation Measured Hours Prior to a Noncontact Anterior Cruciate Ligament Tear

STUDY DESIGN Case report. BACKGROUND Decreased quadriceps activation has been shown to be present following anterior cruciate ligament (ACL) injury, but its presence prior to ACL injury is unknown. The purpose of this case report was to describe the level of quadriceps activation measured hours before a noncontact ACL injury in an individual who previously demonstrated known biomechanical risk factors for ACL injury. CASE DESCRIPTION A 23-year-old female (height, 176.9 cm; mass, 72.4 kg), sustained a left noncontact ACL injury while landing from a jump stop during a recreational basketball game. This case was unique because data regarding landing biomechanics and quadriceps force and activation were gathered in 2 separate, unrelated studies prior to injury. OUTCOMES Peak external knee abduction moment (-65.3 Nm) during a drop jump landing 8 months prior to injury indicated elevated risk for ACL injury. Involved quadriceps central activation ratios (CAR) were obtained 1 week (CAR, 0.81) and 4 hours (CAR, 0.77) prior to injury. Strength and CAR (0.76) measurements changed very little within 36 hours of injury and both strength, and activation (CAR, 0.90) improved following surgical reconstruction and formal rehabilitation. DISCUSSION An individual with known biomechanical risk factors for ACL injury may compound risk for noncontact ACL injury if decreased quadriceps activation is also present. LEVEL OF EVIDENCE Prognosis, level 4.

Sex Differences in Time to Return-to-Play Progression After Sport-Related Concussion

Background: Recently, female sports participation has increased, and there is a tendency for women to experience more symptoms and variable presentation after sport-related concussion (SRC). The purpose of this study was to determine whether sex differences exist in time to begin a return-to-play (RTP) progression after an initial SRC. Hypothesis: After initial SRC, female athletes (11-20 years old) would take longer to begin an RTP progression compared with age-matched male athletes. Study Design: Retrospective cohort study. Level of Evidence: Level 3. Methods: A total of 579 participants (365 males [mean age, 15.0 ± 1.7 years], 214 females [mean age, 15.2 ± 1.5 years]), including middle school, high school, and collegiate athletes who participated in various sports and experienced an initial SRC were included and underwent retrospective chart review. The following information was collected: sex, age at injury, sport, history of prior concussion, date of injury, and date of initiation of RTP progression. Participants with a history of more than 1 concussion or injury sustained from non–sport-related activity were excluded. Results: Despite American football having the greatest percentage (49.2%) of sport participation, female athletes took significantly longer to start an RTP progression after an initial SRC (29.1 ± 26.3 days) compared with age-matched male athletes (22.7 ± 18.3 days; P = 0.002). Conclusion: On average, female athletes took approximately 6 days longer to begin an RTP progression compared with age-matched male athletes. This suggests that sex differences exist between athletes, aged 11 to 20 years, with regard to initiation of an RTP progression after SRC. Clinical Relevance: Female athletes may take longer to recover after an SRC, and therefore, may take longer to return to sport. Sex should be considered as part of the clinical decision-making process when determining plan of care for this population.

Do Muscle Strength Deficits of the Uninvolved Hip and Knee Exist in Young Athletes Before Anterior Cruciate Ligament Reconstruction

Background: Muscle strength of the involved limb is known to be decreased after injury. Comparison with the uninvolved limb has become standard of practice to measure progress and for calculation of limb symmetry indices (LSIs) to determine readiness to return to sport. However, some literature suggests strength changes in the uninvolved limb also are present after lower extremity injury. Purpose: To examine the uninvolved limb strength in a population of adolescent athletes after an anterior cruciate ligament (ACL) injury and compare strength values with those of the dominant limb in a healthy control group. Study Design: Cohort study; Level of evidence, 3. Methods: A total of 64 athletes were enrolled in this study, including 31with injured ACLs (mean age, 15.6 ± 1.4 years) and 33 healthy controls (mean age, 14.9 ± 1.9 years). The median time from injury to testing was 23 days for the ACL-injured group. Participants underwent Biodex isokinetic strength testing at 60 deg/s to assess quadriceps and hamstring strength. Isometric hip strength (abduction, extension, external rotation) was measured using a handheld dynamometer. The muscle strength of the uninvolved limb of the ACL-injured group was compared with that of the dominant limb of the healthy control group. Results: The results showed a significant difference in quadriceps muscle strength between the 2 study groups (P < .001). Isokinetic quadriceps strength of the uninvolved limb in the ACL group was significantly decreased by 25.5% (P < .001) when compared with the dominant limb of the control group. Conclusion: The results of this study demonstrate a decreased isokinetic strength of the quadriceps muscle in the uninvolved limb after ACL injury as compared with healthy controls. Consideration should be taken when using the uninvolved limb for comparison when assessing quadriceps strength in a population with an ACL injury.

The Relationship Between Humeral Retrotorsion and Shoulder Range of Motion in Baseball Players With an Ulnar Collateral Ligament Tear

Background: Humeral retrotorsion has been investigated in relation to shoulder range of motion (ROM) in healthy baseball players. Currently, there is limited information on the osseous anatomy and development of ulnar collateral ligament (UCL) tears. Purpose: To determine the relationship between humeral retrotorsion and shoulder ROM in baseball players with a UCL tear. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Fifty-four baseball players (mean age, 18.5 ± 2.0 years) with a UCL tear volunteered for this study. Participants were measured bilaterally for shoulder internal (IR) and external rotation (ER) ROM and humeral retrotorsion. Differences between sides (involved to uninvolved) were used to calculate the glenohumeral internal rotation deficit (GIRD), external rotation ROM difference (ERDiff), total rotational motion difference (TRM), and humeral retrotorsion difference (HTDiff). A multivariate regression analysis was performed with GIRD, ERDiff, and TRM regressing on HTDiff. Univariate analysis was performed to further evaluate the effect of the predictors on each outcome separately. To control for the effect of age, weight, duration of symptoms, and years of experience, the variables were included as covariates. An a priori level was set at P < .05. Results: There was a statistically significant relationship between the GIRD, ERDiff, and TRM results compared with HTDiff (P = .003). Independent analysis revealed a statistically significant relationship between GIRD and HTDiff (P = .004) and between ERDiff and HTDiff (P = .003) but no significant relationship between TRM and HTDiff (P = .999). After adjusting for age, weight, duration of symptoms, years of experience, dominant arm, and position, a significant relationship was found between GIRD and HTDiff (P = .05) and between ERDiff and HTDiff (P = .01). No significant relationship was found between TRM and HTDiff (P = .54). Adjusted univariate regression analysis determined that HTDiff explains approximately 16% of the variance in GIRD (r 2 = 0.158) and approximately 24% of the variance in ERDiff (r 2 = 0.237). Conclusion: In baseball players with a UCL tear, approximately 16% of the variance in GIRD and 24% of the variance in ERDiff can be attributed to differences found in humeral retrotorsion between sides. This indicates that humeral retroversion contributes significantly to GIRD and increased ER ROM in baseball players. Recognition of differences in humeral retrotorsion between the dominant and nondominant upper extremities may help explain some but not all of the changes in shoulder ROM commonly seen in baseball players.

Energy Absorption Contribution and Strength in Female Athletes at Return to Sport After Anterior Cruciate Ligament Reconstruction: Comparison With Healthy Controls:

Background: Female patients are more likely to suffer a second anterior cruciate ligament (ACL) injury after ACL reconstruction (ACLR) and return to sport (RTS) compared with healthy female controls. Few studies have examined the energy absorption contribution (EAC) that could lead to this subsequent injury. Hypothesis: The ACLR group would demonstrate an altered EAC between joints (hip, knee, and ankle) but no difference in quadriceps, hip abduction, or hip external rotation (ER) strength at the time of RTS. Study Design: Cross-sectional study; Level of evidence, 3. Methods: A total of 34 female participants (ACLR: n = 17; control: n = 17) were enrolled in the study and matched for age and activity level. Jump landing performance for the initial 50 milliseconds of landing of a lateral-vertical jump was assessed using a 10-camera 3-dimensional motion capture system and 2 force plates. Isokinetic quadriceps strength was measured using a Biodex machine, and hip abduction and ER isometric strength were measured using a handheld dynamometer. All values were normalized to the participant’s height and weight. A 1-way multivariate analysis of variance was used to assess between-group differences in the EAC at the hip, knee, and ankle. Two 1-way analyses of variance were used to independently examine quadriceps, hip abduction, and hip ER strength between the groups. Results: Significant differences in the EAC were found between the groups for the involved hip (P = .002), uninvolved hip (P = .005), and involved ankle (P = .023). There were no between-group differences in the EAC for the involved or uninvolved knee or the uninvolved ankle. Patients who underwent ACLR demonstrated significantly decreased quadriceps strength on the involved limb (P = .02) and decreased hip ER strength on both the involved (P = .005) and uninvolved limbs (P = .002). No significant strength differences were found between the groups for the uninvolved quadriceps or for involved or uninvolved hip abduction. Conclusion: At RTS, patients who underwent ACLR utilized a greater hip EAC bilaterally and a decreased involved ankle EAC during a lateral-vertical jump. Furthermore, quadriceps strength on the involved limb and hip ER strength of bilateral lower extremities remained decreased. This could place greater stress on the ACL graft and ultimately lead to an increased injury risk.

Participants at three months post-operative anterior cruciate ligament reconstruction (ACL-R) demonstrate differences in lower extremity energy absorption contribution and quadriceps strength compared to healthy controls

BACKGROUND The purpose of this study was to compare hip and knee energy absorption contribution (EAC) during a double limb squat (DLS) and quadriceps strength in patients three months post-operative ACL-R versus matched healthy controls. METHODS Twenty-four ACL-R participants (Age = 15.5 ± 1.3 yrs; Ht = 1.66 ± .07 m; Mass = 66.3 ± 15.5 kg) were compared to 24 age, sex, limb, and activity-matched healthy controls (Age = 15.5 ± 1.2 yrs; Ht = 1.65 ± .08 m; Mass = 59.0 ± 9.8 kg). Lower extremity biomechanical data was collected at three months post-operative ACL-R during five consecutive DLS. EAC was calculated during DLS descent. Isokinetic quadriceps strength was collected at 60°/s. Normalized quadriceps peak torque (QUADS) was averaged across five trials. Independent t-tests examined differences in group hip and knee EAC during each task. Separate Pearson product-moment correlations examined the relationship between QUADS and hip and knee EAC during the DLS. RESULTS ACL-R demonstrated greater injured limb hip EAC (46.4 ± 16.0) than Healthy (31.7 ± 11.0) during a DLS (p = 0.001). ACL-R demonstrated less injured limb knee EAC (42.7 ± 14.6) than Healthy (60.6 ± 8.9) during DLS (p < 0.001). No differences were seen between uninjured limb hip (ACL-R = 0.0 ± 14.2; Healthy = 33.4 ± 9.1, p = 0.629) or knee (ACL-R = 56.9 ± 15.6; Healthy = 59.1 ± 9.8, p = 0.561) EAC and matched limbs. ACL-R injured limb QUADS was decreased compared to Healthy (ACL-R = 1.1 ± 0.5; Healthy = 2.0 ± 0.5, p < 0.001). No differences were seen in QUADS on the uninjured and matched limbs (ACL-R = 2.0 ± 0.6; Healthy = 1.9 ± 0.5, p = 0.894). There was a weak, negative correlation between injured limb QUADS and hip EAC (r = -0.471, p = 0.001) and moderate, positive correlation between injured limb QUADS and knee EAC (r = 0.615, p < 0.001). CONCLUSIONS ACL-R participants demonstrate different eccentric loading strategies during a DLS at three months postoperative compared to matched healthy controls.

Correlation among Y Balance Test-Lower Quarter Composite Scores, Hip Musculoskeletal Characteristics, and Pitching Kinematics in NCAA Division I Baseball Pitchers

Context: Numerous studies have reported kinematic data on baseball pitchers using three-dimensional (3D) motion analysis, but no studies to date have correlated this data with clinical outcome measures. Objective: To examine the relationship among Y-Balance Test-Lower Quarter (YBT-LQ) composite scores, musculoskeletal characteristics of the hip, and pitching kinematics in National Collegiate Athletic Association (NCAA) Division I baseball pitchers. Design: Cross-sectional. Setting: 3D motion analysis laboratory. Participants: Nineteen healthy male college baseball pitchers. Main Outcome Measures: Internal and external hip passive range of motion, hip abduction strength, YBT-LQ composite scores, and kinematic variables of the pitching motion. Results: Stride length demonstrated a moderate positive correlation with dominant limb YBT-LQ composite score (r = .524, P = .02) and nondominant limb YBT-LQ composite score (r = .550, P = .01), and a weak positive correlation with normalized time to maximal humerus velocity (r = .458, P = .04). Stride length had a moderate negative correlation with normalized time to maximal thorax velocity (r = -.522, P = .02) and dominant hip total rotational motion (TRM; r = -.660, P = .002), and had a strong negative correlation with normalized time from stride foot contact to maximal knee flexion (r = -.722, P < .001). Dominant limb YBT-LQ composite score had a weak negative correlation with hip abduction strength difference (r = -.459, P = .04) and normalized time to maximal thorax velocity (r = -.468, P = .04). Nondominant limb YBT-LQ composite score demonstrated a weak negative correlation with normalized time to maximal thorax velocity (r = -.450, P = .05) and had a moderate negative correlation with dominant hip TRM (r = -.668, P = .001). There were no other significant relationships between the remaining variables. Conclusions: YBT-LQ is a clinical measure that can be used to correlate with hip musculoskeletal characteristics and pitching kinematics in NCAA Division I pitchers.