Force-plate derived predictors of lateral jump performance in NCAA Division-I men's basketball players.

A lateral jump assessment may provide unique benefits in sports such as basketball that require multidirectional performance optimization. This study aimed to examine selected force-plate derived metrics as predictors of lateral jump task distance in men's basketball players. Twenty-two NCAA Division-I men's basketball players (19.4 ± 1.3 years, 95.0 ± 12.5 kg, 196.5 ± 8.1 cm) each performed six single leg lateral jumps while standing on a force plate (1200 Hz, Kistler Instrument Corp). The lateral jump task involved the subject beginning by standing on the force plate and jumping sideways off one foot and then landing on the floor with the opposite foot. Three-dimensional ground reaction force curves were used to identify the eccentric and concentric phases of the jump and variables were computed each from the lateral (y), vertical (z), and resultant (r) force traces. Peak ground reaction force (pGRF), ground reaction force angle (θr), eccentric braking rate of force development (ECC-RFD), average concentric force (CON-AVG), total jump duration, eccentric phase duration, and eccentric to total time ratio were evaluated for predictive ability. Three regression models were able to significantly (p<0.05) predict jump distance: (1) pGRFy, pGRFz, and θr (p<0.001, R2 = 0.273), (2) Relative pGRFy, Relative pGRFz, and θr ((p<0.001, R2 = 0.214), and (3) Relative CON-AVGy and Relative pGRFr (p<0.001, R2 = 0.552). While several force plate-derived metrics were identified as significant predictors, a model with Relative CON-AVGy and Relative pGRFr explained a greater variability in performance (R2 = 0.55) compared to the other variables which were low, yet also significant. These results suggest that lateral ground reaction forces can be used to evaluate lateral jump performance with the use of three-dimensional force plates. The identified predictors can be used as a starting point for performance monitoring, as basketball training interventions can be directed at specific improvements in the identified metrics.

Isometric Knee Strength is Greater in Individuals Who Score Higher on Psychological Readiness to Return to Sport After Primary Anterior Cruciate Ligament Reconstruction.

Background: Anterior cruciate ligament (ACL) injury is extremely common among athletes. Rate of second ACL injury due to surgical graft rupture or contralateral limb ACL injury is approximately 15-32%. Psychological readiness to return to sport (RTS) may be an important predictor of successful RTS outcomes. Psychological readiness can be quantified using the ACL Return to Sport after Injury (ACL-RSI) questionnaire, with higher scores demonstrating greater psychological readiness. Purpose: The purpose of this study was to investigate differences in functional performance and psychological readiness to return to sport among athletes who have undergone primary ACL reconstruction (ACLR). Study Design: Descriptive cohort study. Methods: Eighteen athletes who had undergone primary ACLR were tested at time of RTS clearance. The cohort was divided into two groups, high score (HS) and low score (LS), based on median ACL-RSI score, and performance on static and dynamic postural stability testing, lower extremity isokinetic and isometric strength testing, and single leg hop testing was compared between the groups using an independent samples t-test. Results: The median ACL-RSI score was 74.17. The average ACL-RSI score was 83.1±6.2 for the HS group and 61.8±8.0 for the LS group. High scorers on the ACL-RSI performed significantly better on isometric knee flexion as measured via handheld dynamometry (22.61% ±6.01 vs. 12.12% ±4.88, p=0.001) than the low score group. Conclusion: The findings suggest that increased knee flexion strength may be important for psychological readiness to RTS after primary ACLR. Further research is indicated to explore this relationship, however, a continued emphasis on improving hamstring strength may be appropriate during rehabilitation following ACLR to positively impact psychological readiness for RTS. Level of Evidence: III.

Females have Lower Knee Strength and Vertical Ground Reaction Forces During Landing than Males Following Anterior Cruciate Ligament Reconstruction at the Time of Return to Sport.

Purpose: There is a high rate of second anterior cruciate ligament (ACL) injury (ipsilateral graft or contralateral ACL) upon return-to-sport (RTS) following ACL reconstruction (ACLR). While a significant amount of epidemiological data exists demonstrating sex differences as risk factors for primary ACL injury, less is known about sex differences as potential risk factors for second ACL injury. The purpose of this study is to determine if there are sex-specific differences in potential risk factors for second ACL injury at the time of clearance for RTS. Methods: Ten male and eight female athletes (age: 20.8 years ±6.3, height: 173.2 cm ±10.1, mass: 76.6 kg ±18.3) participated in the study following ACLR at time of RTS (mean 10.2 months). Performance in lower extremity isokinetic and isometric strength testing, static and dynamic postural stability testing, and a single leg stop-jump task was compared between the sexes. Results: Normalized for body weight, males had significantly greater isokinetic knee flexion (141±14.1 Nm/kg vs. 78±27.4 Nm/kg, p=0.001) and extension strength (216±45.5 Nm/kg vs. 159±53.9 Nm/kg, p=0.013) as well as isometric flexion (21.1±6.87% body weight vs. 12.5±5.57% body weight, p=0.013) and extension (41.1±7.34% body weight vs. 27.3±11.0% body weight, p=0.016) strength compared to females. In the single-leg stop jump task, males had a greater maximum vertical ground reaction force during landing (332±85.5% vs. 259±27.4% body weight, p=0.027) compared to females. Conclusions: Based on these results, there are significant differences between sexes following ACLR at the time of RTS. Lower knee flexion and extension strength may be a potential risk factor for second ACL injury among females. Alternatively, the increased maximum vertical force observed in males may be a potential risk factor of second ACL injury in males. Although these results should be interpreted with some caution, they support that rehabilitation programs in the post-ACLR population should be individualized based on the sex of the individual. Level of Evidence: Level 3.

Clinical Measures of Adolescent Softball Players With and Without Upper-Extremity Pain: A Preliminary Study.

CONTEXT: Upper-extremity (UE) pain is a concern among softball adolescent athletes. However, research on preseason screening of demographic characteristics and clinical measures among those with and without UE pain among adolescent softball athletes is underreported. This study sought to present functional outcomes and clinical measures of shoulder and hip complex flexibility, range of motion (ROM), and strength in adolescent softball athletes with and without UE pain. DESIGN: Cross-sectional study. METHODS: Sixty-seven athletes were assessed at the start of the spring season. The Kerlan-Jobe Orthopedic Clinic Shoulder and Elbow Questionnaire was administered to determine UE function. UE measurements included shoulder ROM, flexibility, and strength; lower-extremity measurements included hip ROM and strength. These variables were reported for players with and without UE pain as mean and SD. Independent samples t tests were performed to analyze differences between the groups. RESULTS: Thirteen (19.4%) athletes reported UE pain during preseason screening. Mean Kerlan-Jobe Orthopedic Clinic Shoulder and Elbow Questionnaire score among athletes with UE pain was 58.0 (17.6) compared with 97.1 (6.9) for athletes reporting no UE pain (P < .001). Athletes with UE pain presented with significantly less dominant side external rotation ROM (UE pain: 106.5 [10.4], no UE pain: 114.6 [11.3]) and total ROM (UE pain: 163.7 [14.5], no UE Pain: 174.8 [14.3]). CONCLUSION: These findings inform clinicians on function and preseason clinical measures in adolescent softball athletes who present with or without UE pain. Athletes with UE pain demonstrated lower outcome scores indicating likely impact on overall UE function. These athletes also appeared to demonstrate UE ROM differences compared with athletes without UE pain. Further research is needed to investigate larger sample sizes and positional differences at baseline and throughout the season to determine if clinical measures used in the current study are risk factors for pain and injury.

Altered lower extremity biomechanics following anterior cruciate ligament reconstruction during single-leg and double-leg stop-jump tasks: A bilateral total support moment analysis.

BACKGROUND: Injury to the anterior cruciate ligament (ACL) can lead to long-lasting biomechanical alterations that put individuals at risk of a second ACL injury. Examining the total support moment may reveal between- and within-limb compensatory strategies. METHODS: Twenty-six participants who were cleared to return to sport following ACL reconstruction were recruited. Each participant completed the single-leg and double-leg stop jump tasks. These tasks were analyzed using force plates and a 3D motion analysis system. The total support moment was calculated by summing the internal moments of the hip, knee and ankle at peak vertical ground reaction force. FINDINGS: Internal knee extensor moment was lower in the involved limb compared to the uninvolved for both tasks (17.6%, P = 0.022; 18.4%, P = 0.008). No significant between-limb differences were found for the total support moment. The involved limb exhibited an 18.2% decrease in knee joint contribution (P = 0.01) and a 21.6% increase in ankle joint contribution (P = 0.016) to the total support moment compared to the uninvolved limb in the single-leg stop jump task. INTERPRETATION: Compensation for the involved knee is likely due to altered biomechanics that redistributes load to the uninvolved knee or to adjacent joints of the same limb. A partial shift in joint contribution from the knee to the ankle during the single-leg stop jump task demonstrates a tendency to decrease load to the knee. Further studies are needed to investigate how these adaptations impact the prevalence of subsequent injury and poor joint health.

The Relationship Between Hip Strength and Postural Stability in Collegiate Athletes Who Participate in Lower Extremity Dominant Sports.

BACKGROUND: Lower extremity (LE) injuries are common across many sports. Both core strength (including hip strength) deficits and poor postural stability have been linked to lower extremity (LE) injury. The relationship between these two characteristics is unknown. PURPOSE: To explore the relationships between hip strength, static postural stability, and dynamic postural stability. STUDY DESIGN: Descriptive Cross-Sectional Study. METHODS: 162 Division I student-athletes (111 males and 51 females) participated in this study. Isometric hip strength was measured using a hand-held dynamometer and both single-leg static (eyes open EO and eyes closed EC) and dynamic postural stability were assessed with a force plate. Pairwise correlations were calculated to examine the relationship between the hip strength variables and the postural stability scores for all subjects and separately for males and females. RESULTS: There were no significant correlations between hip strength and dynamic postural stability for any of the pairwise correlations. Significant, albeit minimal, correlations between EO and EC static postural stability and each of the hip strength variables for all subjects and male subjects (correlation coefficients ranged from -0.19 to -0.34). However, there were only two significant correlations between hip strength and EC static postural stability (hip internal/external rotation) and one for hip strength and EO postural stability (hip internal rotation) found for female subjects (correlation coefficients ranged from -0.28 to -0.31). CONCLUSION: There was no relationship between isometric hip strength and dynamic postural stability; whereas, there were some relationships between the strength measures and static postural stability. These significant, but minimal correlations were observed in more of the comparisons within the male cohort potentially demonstrating a sex difference. LEVEL OF EVIDENCE: 3b.

Upper Extremity Musculoskeletal Characteristics and the Kerlan-Jobe Orthopaedic Clinic Questionnaire Score in Collegiate Baseball Athletes.

CONTEXT: Upper extremity (UE) musculoskeletal injuries are common in baseball athletes due to the increased demand placed on the UE. The link between risk factors for UE musculoskeletal injuries and baseball athletes' perceived UE function and pain, as measured by the Kerlan-Jobe Orthopaedic Clinic (KJOC) questionnaire, is unclear. OBJECTIVE: To (1) describe the musculoskeletal characteristics of the UE (posture, range of motion, flexibility, and isometric strength) in a population of baseball athletes and (2) determine the predictive capability of UE musculoskeletal characteristics for the KJOC score in these athletes. DESIGN: Cohort study. SETTING: Athletic training room. PATIENTS OR OTHER PARTICIPANTS: A total of 37 male National Collegiate Athletic Association Division I baseball athletes (age = 20.10 ± 1.27 years, height = 186.96 ± 7.64 cm, mass = 90.60 ± 10.69 kg). INTERVENTION(S): Athletes self-reported all shoulder musculoskeletal injuries and completed the KJOC questionnaire. Postural assessment consisted of forward head and shoulder posture. Flexibility tests characterized glenohumeral internal and external rotation, posterior shoulder tightness, and pectoralis minor length. Strength tests involved the lower and middle trapezius, rhomboid, glenohumeral internal and external rotation, pectoralis major, serratus anterior, supraspinatus, and upper trapezius. MAIN OUTCOME MEASURE(S): All 10 KJOC questions were summed for an overall score out of 100. Questions 1 through 5 were summed for a pain score; questions 6 through 10 were summed for a function score. All data were assessed for normality. A stepwise multiple regression model was fit to determine if the predictor variables assessed could predict the KJOC score. We set the α level a priori at .05. RESULTS: For the KJOC total score, a 1-year history of shoulder injury accounted for 7.80% of the variance in the KJOC total score (P = .07). For KJOC questions 1 through 5, a history of UE injury in the year before testing and posterior shoulder tightness accounted for 14.40% of the variance in the KJOC total score (P = .047). CONCLUSIONS: The link between a history of UE musculoskeletal injuries and the KJOC score highlights the need for continued focus on self-perceived pain and function after UE musculoskeletal injury.

The Warrior Model for Human Performance Optimization.

Special Operations Combat Personnel (SOCP) face significant challenges and occupational demands that put them at significant risk for musculoskeletal injury. Musculoskeletal injury leads to lost-duty days, medical disqualification, and compromises operational readiness and mission success. Optimizing human performance and developing injury prevention strategies can position SOCP for success, but human performance optimization is a complex process that demands the integration of multiple disciplines to address a broad range of capabilities necessary for this success. The Warrior Model for Human Performance Optimization outlines a step-by-step approach to human performance optimization embedded within a scientific, evidenced-based approach to injury prevention and performance optimization that includes a step to ensure specificity of training and interventions. This evidence-based approach can insure that SOCP capabilities match the demands of occupation enabling them to successfully execute their occupation tasks without risk of injury. While the focus of this review is on military personnel, the same principles have application to nonmilitary high-performance athletes.

Shoulder Range of Motion and Baseball Arm Injuries: A Systematic Review and Meta-Analysis.

OBJECTIVE: Arm injuries in baseball players are a common problem. The identification of modifiable risk factors, including range of motion (ROM), is essential for injury prevention. The purpose of this review was to assess the methodologic quality and level of evidence in the literature and to investigate the relationship between shoulder ROM and the risk of arm injuries in baseball players. DATA SOURCES: Relevant studies in PubMed, CINAHL, Embase, and SPORTDiscus published from inception to August 1, 2017. STUDY SELECTION: Only studies that encompassed healthy baseball cohorts who were assessed for shoulder ROM and prospectively evaluated for injuries throughout a baseball season or seasons were included. DATA EXTRACTION: Six articles met the search criteria. Only 3 studies were included in the meta-analysis due to disparate participant groups. DATA SYNTHESIS: The modified Downs and Black scale (0-15 points) was used to analyze methodologic quality. Study quality ranged from 11 to 14. Four studies received high-quality (≥12) and 2 studies received moderate-quality (≥10) scores. The overall pooled analysis demonstrated that absolute and internal-rotation deficits (-5.93 [95% confidence interval {CI} = -9.43, -2.43], P < .001 and 4.28 [0.71, 7.86], P = .02, respectively) and absolute total ROM (TROM; -6.19 [95% CI = -10.28, -2.10]; P = .003) were predictors of injury, and these data exhibited homogeneity (absolute IR P value = .77, I2 = 0%; IR deficit P value = .41, I2 = 0%; absolute TROM P value = .78, I2 = 0%). No significance was observed for absolute external rotation (-2.86 [95% CI = -6.56, 0.83], P = .13), which had data with high heterogeneity ( P = .003; I2 = 83%). A deficit in horizontal adduction was a predictor of injury (-8.32 [95% CI = -12.08, -4.56]; P < .001); these data were homogeneous but yielded a moderate heterogenic effect ( P = .16; I2 = 50%). CONCLUSIONS: High-quality evidence demonstrated that deficits in throwing-arm TROM and IR were associated with upper extremity injury in baseball players. Heterogeneity across studies for horizontal adduction suggested that this may be a modifiable risk factor for injury, but it requires further research.

The Relationship of Core Strength and Activation and Performance on Three Functional Movement Screens.

Johnson, CD, Whitehead, PN, Pletcher, ER, Faherty, MS, Lovalekar, MT, Eagle, SR, and Keenan, KA. The relationship of core strength and activation and performance on three functional movement screens. J Strength Cond Res 32(4): 1166-1173, 2018-Current measures of core stability used by clinicians and researchers suffer from several shortcomings. Three functional movement screens appear, at face-value, to be dependent on the ability to activate and control core musculature. These 3 screens may present a viable alternative to current measures of core stability. Thirty-nine subjects completed a deep squat, trunk stability push-up, and rotary stability screen. Scores on the 3 screens were summed to calculate a composite score (COMP). During the screens, muscle activity was collected to determine the length of time that the bilateral erector spinae, rectus abdominis, external oblique, and gluteus medius muscles were active. Strength was assessed for core muscles (trunk flexion and extension, trunk rotation, and hip abduction and adduction) and accessory muscles (knee flexion and extension and pectoralis major). Two ordinal logistic regression equations were calculated with COMP as the outcome variable, and: (a) core strength and accessory strength, (b) only core strength. The first model was significant in predicting COMP (p = 0.004) (Pearson's Chi-Square = 149.132, p = 0.435; Nagelkerke's R-Squared = 0.369). The second model was significant in predicting COMP (p = 0.001) (Pearson's Chi-Square = 148.837, p = 0.488; Nagelkerke's R-Squared = 0.362). The core muscles were found to be active for most screens, with percentages of "time active" for each muscle ranging from 54-86%. In conclusion, performance on the 3 screens is predicted by core strength, even when accounting for "accessory" strength variables. Furthermore, it seems the screens elicit wide-ranging activation of core muscles. Although more investigation is needed, these screens, collectively, seem to be a good assessment of core strength.

Point of Care Quantitative Assessment of Muscle Health in Older Individuals: An Investigation of Quantitative Muscle Ultrasound and Electrical Impedance Myography Techniques.

Background: Muscle health is recognized for its critical role in the functionality and well-being of older adults. Readily accessible, reliable, and inexpensive methods of measuring muscle health are needed to advance research and clinical care. Methods: In this prospective, blinded study, 27 patients underwent quantitative muscle ultrasound (QMUS), standard electrical impedance myography (sEIM), and handheld electrical impedance myography (hEIM) of the anterior thigh musculature by two independent examiners. Subjects also had dual-energy X-ray absorptiometry (DEXA) scans and standardized tests of physical function and strength. Data were analyzed for intra- and inter-rater reliability, along with correlations with DEXA and physical measures. Results: Measures of intra- and inter-rater reliability were excellent (>0.90) for all QMUS, sEIM, and hEIM parameters except intra-rater reliability of rectus femoris echointensity (0.87-0.89). There were moderate, inverse correlations between QMUS, sEIM, and hEIM parameters and measures of knee extensor strength. Moderate to strong correlations (0.57-0.81) were noted between investigational measures and DEXA-measured fat mass. Conclusions: QMUS, sEIM and hEIM were highly reliable in a controlled, same-day testing protocol. Multiple correlations with measures of strength and body composition were noted for each method. Point-of-care technologies may provide an alternative means of measuring health.