College Soccer Student-Athletes Demonstrate Differences in Self-Reported Athlete Health When Grouped by Match Volume.

CONTEXT: Physical changes following activity are well documented, but there is limited information about self-reported outcomes around competitive matches. High training volumes and poor recovery could predispose athletes to overuse injury. The purpose of this study was to identify the changes in daily athlete health measures before, during, and after the day of each match in high- and low-volume groups. DESIGN: Prospective cohort. METHODS: Fifty-five soccer athletes (age: 19.8 [1.2] y, 26 males, 29 females) provided daily measures of readiness, physical fatigue, mental stress, sleep quality, and soreness intensity match days, days 1 (D01) and 2 (D02) following matches, and standard practice days. Participants were grouped into high volume and low volume, based off the minutes played during the season. RESULTS: Soreness increased, readiness decreased, and fatigue increased on D01 compared with match days (P < .008) in the high-volume group. Between groups, the high-volume group demonstrated higher soreness on D01 and D02, lower readiness on D01 and D02, and lower fatigue on D01, compared with the low-volume group (P < .008). CONCLUSIONS: Soccer athletes demonstrate significant changes in self-reported athlete health variables around competitive matches. These changes are similar to physical outcomes, potentially indicating that the athlete health variables may be used to track athlete recovery from competition, potentially limiting the impact of overuse injuries.

Demographic Factors and Instantaneous Lower Extremity Injury Occurrence in a National Collegiate Athletic Association Division I Population.

CONTEXT: Temporal prediction of the lower extremity (LE) injury risk will benefit clinicians by allowing them to better leverage limited resources and target those athletes most at risk. OBJECTIVE: To characterize the instantaneous risk of LE injury by demographic factors of sex, sport, body mass index (BMI), and injury history. DESIGN: Descriptive epidemiologic study. SETTING: National Collegiate Athletic Association Division I athletic program. PATIENTS OR OTHER PARTICIPANTS: A total of 278 National Collegiate Athletic Association Division I varsity student-athletes (119 males, 159 females; age = 19.07 ± 1.21 years, height = 175.48 ± 11.06 cm, mass = 72.24 ± 12.87 kg). MAIN OUTCOME MEASURE(S): Injuries to the LE were tracked for 237 ± 235 consecutive days. Sex-stratified univariate Cox regression models were used to investigate the association between time to first LE injury and sport, BMI, and LE injury history. The instantaneous LE injury risk was defined as the injury risk at any given point in time after the baseline measurement. Relative risk ratios and Kaplan-Meier curves were generated. Variables identified in the univariate analysis were included in a multivariate Cox regression model. RESULTS: Female athletes displayed similar instantaneous LE injury risk to male athletes (hazard ratio [HR] = 1.29; 95% CI= 0.91, 1.83; P = .16). Overweight athletes (BMI >25 kg/m2) had similar instantaneous LE injury risk compared with athletes with a BMI of <25 kg/m2 (HR = 1.23; 95% CI = 0.84, 1.82; P = .29). Athletes with previous LE injuries were not more likely to sustain subsequent LE injury than athletes with no previous injury (HR = 1.09; 95% CI = 0.76, 1.54; P = .64). Basketball (HR = 3.12; 95% CI = 1.51, 6.44; P = .002) and soccer (HR = 2.78; 95% CI = 1.46, 5.31; P = .002) athletes had a higher risk of LE injury than cross-country athletes. In the multivariate model, instantaneous LE injury risk was greater in female than in male athletes (HR = 1.55; 95% CI = 1.00, 2.39; P = .05), and it was greater in male athletes with a BMI of >25 kg/m2 than that in all other athletes (HR = 0.44; 95% CI = 0.19, 1.00; P = .05), but these findings were not significantly different. CONCLUSIONS: In a collegiate athlete population, previous LE injury was not a contributor to the risk of future LE injury, whereas being female or being male with a BMI of >25 kg/m2 resulted in an increased risk of LE injury. Clinicians can use these data to extrapolate the LE injury risk occurrence to specific populations.

Examining the effects of femoral anteversion and passive hip rotation on ACL injury and knee biomechanics: a systematic review and meta-analysis.

PURPOSE: Greater femoral internal rotation (via anteversion or passive hip ROM) is associated with knee biomechanics thought to contribute to anterior cruciate ligament (ACL) injury, but it is unknown if femoral internal rotation contributes to actual ACL injury occurrence. The objective of this systematic review and meta-analysis was to quantify the extent to which femoral anteversion and hip range of motion (ROM) influence knee biomechanics consistent with ACL injury and actual ACL injury occurrence. METHODS: Using PRISMA guidelines, PubMed, CINAHL, SportDiscus, and Scopus databases were searched. Inclusion criteria were available passive hip ROM or femoral anteversion measure, ACL injury OR biomechanical analysis of functional task. Two reviewers independently reviewed titles, abstracts, and full texts when warranted. Included studies were submitted to Downs & Black Quality Assessment Tool. Meta-analyses were conducted for comparisons including at least two studies. RESULTS: Twenty-three studies were included (11 injury outcome, 12 biomechanical outcome). Decreased internal rotation ROM was significantly associated with history of ACL injury (MD -5.02°; 95% CI [-8.77°--1.27°]; p = 0.01; n = 10). There was no significant effect between passive external rotation and ACL injury (MD -2.62°; 95% CI [-5.66°-- 0.41°]; p = 0.09; n = 9) Participants displaying greater frontal plane knee projection angle had greater passive external rotation (MD 4.77°; 95% CI [1.17° - 8.37°]; p = 0.01; n = 3). There was no significant effect between femoral anteversion and ACL injury (MD -0.46°; 95% CI [-2.23°-1.31°]; p = 0.61; n = 2). No within-sex differences were observed between injured and uninjured males and females (p range = 0.09 - 0.63). CONCLUSION: Though individuals with injured ACLs have statistically less passive internal and external rotation, the observed heterogeneity precludes generalizability. There is no evidence that femoral anteversion influences biomechanics or ACL injury. Well-designed studies using reliable methods are needed to investigate biomechanical patterns associated with more extreme ROM values within each sex, and their prospective associations with ACL injury. LEVEL OF EVIDENCE: IV.

Ankle Dorsiflexion Affects Hip and Knee Biomechanics During Landing.

BACKGROUND: Restricted ankle dorsiflexion range of motion (DFROM) has been linked to lower extremity biomechanics that place an athlete at higher risk for injury. Whether reduced DFROM during dynamic movements is due to restrictions in joint motion or underutilization of available ankle DFROM motion is unclear. HYPOTHESIS: We hypothesized that both lesser total ankle DFROM and underutilization of available motion would lead to high-risk biomechanics (ie, greater knee abduction, reduced knee flexion). STUDY DESIGN: Cross-sectional study. LEVEL OF EVIDENCE: Level 3. METHODS: Nineteen active female athletes (age, 20.0 ± 1.3 years; height, 1.61 ± 0.06 m; mass, 67.0 ± 10.7 kg) participated. Maximal ankle DFROM (clinical measure of ankle DFROM [DF-CLIN]) was measured in a weightbearing position with the knee flexed. Lower extremity biomechanics were measured during a drop vertical jump with 3-dimensional motion and force plate analysis. The percent of available DFROM used during landing (DF-%USED) was calculated as the peak DFROM observed during landing divided by DF-CLIN. Univariate linear regressions were performed to identify whether DF-CLIN or DF-%USED predicted knee and hip biomechanics commonly associated with injury risk. RESULTS: For every 1.0° less of DF-CLIN, there was a 1.0° decrease in hip flexion excursion (r2 = 0.21, P = 0.05), 1.2° decrease in peak knee flexion angles (r2 = 0.37, P = 0.01), 0.9° decrease in knee flexion excursion (r2 = 0.40, P = 0.004), 0.002 N·m·N-1·cm-1 decrease in hip extensor work (r2 = 0.28, P = 0.02), and 0.001 N·m·N-1·cm-1 decrease in knee extensor work (r2 = 0.21, P = 0.05). For every 10% less of DF-%USED, there was a 3.2° increase in peak knee abduction angles (r2 = 0.26, P = 0.03) and 0.01 N·m·N-1·cm-1 lesser knee extensor work (r2 = 0.25, P = 0.03). CONCLUSION: Lower levels of both ankle DFROM and DF-%USED are associated with biomechanics that are considered to be associated with a higher risk of sustaining injury. CLINICAL RELEVANCE: While total ankle DFROM can predict some aberrant movement patterns, underutilization of available ankle DFROM can also lead to higher risk movement strategies. In addition to joint specific mobility training, clinicians should incorporate biomechanical interventions and technique feedback to promote the utilization of available motion.

Female Athletes With Varying Levels of Vertical Stiffness Display Kinematic and Kinetic Differences During Single-Leg Hopping.

Vertical stiffness may contribute to lower-extremity injury risk; however, it is unknown whether athletes with different stiffness levels display differences in biomechanics. This study compared differences in biomechanics between female athletes (n = 99) with varying stiffness levels during a repetitive, single-leg, vertical hopping task. Vertical stiffness was calculated as the ratio of peak vertical ground-reaction force to maximum center-of-mass displacement. Tertiles were established using stiffness values, and separate 1-way ANOVAs were used to evaluate between-group differences. Stance times decreased, and flight times, ground-reaction force, and stiffness increased, from the low- to high-stiffness group (P < .050). The high-stiffness group displayed: (1) greater lateral trunk flexion (P = .009) and lesser hip adduction (P = .022) at initial ground contact compared to the low- and moderate-stiffness groups, respectively; (2) lesser peak hip adduction compared to the low-stiffness group (P = .040); (3) lesser lateral trunk-flexion (P = .046) and knee-flexion (P = .010) excursion compared to the moderate- and low-stiffness groups, respectively; and (4) greater peak hip-flexion (P = .001), ankle-dorsiflexion (P = .002), and ankle-eversion (P = .038) moments compared to the low-stiffness group. A wide range of variability in stiffness exists within a relatively homogenous population. Athletes with varying stiffness levels display biomechanical differences that may help identify the potential mechanism(s) by which stiffness contributes to injury risk.

Bilateral quadriceps and hamstrings muscle volume asymmetries in healthy individuals.

Determining the magnitude of quadriceps and hamstring muscle volume asymmetries in healthy individuals is a critical first step toward interpreting asymmetries as compensatory or abnormal in pathological populations. The purpose of this study was to determine the magnitude of whole and individual muscle volume asymmetries, quantified as right-left volume differences, for the quadriceps and hamstring muscles in a young and healthy population. Twenty-one healthy individuals participated: Eleven females age = 22.6 ± 2.9 years and 10 males age = 23.2 ± 3.4 years. Whole muscle group and individual muscle volume asymmetries were quantified within the context of absolute measurement error using a 95% Limits of Agreement approach. Mean muscle asymmetries ranged from -3.0 to 6.0% for all individual and whole muscle groups. Whole muscle group 95% limits of agreements represented ±11.4% and ±8.8% volume asymmetries for the hamstrings and quadriceps, respectively. Individual muscle asymmetry 95% limits of agreements ranged from ∼ ± 11-13% for the vastii muscles while the biceps femoris short-head (±33.5%), long-head (±20.9%), and the rectus femoris (±21.4%) displayed the highest relative individual asymmetries. Individual muscle asymmetries exceeded absolute measurement error in 70% of all cases, with 26% of all cases exceeding 10% asymmetry. Although whole muscle group asymmetries appear to be near the 10% assumed clinical threshold of normality, the greater magnitude of individual muscle asymmetries highlights the subject- and muscle-specific variability in volume asymmetry. Future research is warranted to determine if volume asymmetry thresholds exist that discriminate between healthy and pathological populations. Statement of Clinical Significance: Muscle volume asymmetries displayed in healthy individuals provide a reference for interpreting asymmetries in pathological populations. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:963-970, 2018.

Relationships of hamstring muscle volumes to lateral tibial slope.

BACKGROUND: Greater posterior-inferior directed slope of the lateral tibial plateau (LTS) has been demonstrated to be a prospective ACL injury risk factor. Trainable measures to overcome a greater LTS need to be identified for optimizing injury prevention protocols. It was hypothesized that Healthy individuals with greater LTS who have not sustained an ACL injury would have a larger lateral hamstring volume. METHODS: Eleven healthy females (mean +/- standard deviation) (1.63±0.07m, 62.0±8.9kg, 22.6±2.9years) & 10 healthy males (1.80±0.08m, 82.3±12.0kg, 23.2±3.4years) underwent magnetic resonance imaging of the left knee and thigh. LTS, semitendinosus muscle volume, and biceps femoris long head muscle volume were obtained from imaging data. RESULTS: After controlling for potential sex confounds (R2=.00; P=.862), lesser semitendinosus volume and greater biceps femoris-long head volume were indicative of greater LTS (R2∆=.30, P=.008). CONCLUSIONS: Healthy individuals with greater LTS have a muscular morphologic profile that includes a larger biceps femoris-long head volume. This may be indicative of a biomechanical strategy that relies more heavily on force generation of the lateral hamstring and is less reliant on force generation of the medial hamstring. LEVEL OF EVIDENCE: Level IV.

The Interday Measurement Consistency of and Relationships Between Hamstring and Leg Musculo-articular Stiffness.

Hamstring stiffness (K(HAM)) and leg stiffness (K(LEG)) are commonly examined relative to athletic performance and injury risk. Given these may be modifiable, it is important to understand day-to-day variations inherent in these measures before use in training studies. In addition, the extent to which K(HAM) and K(LEG) measure similar active stiffness characteristics has not been established. We investigated the interday measurement consistency of K(HAM) and K(LEG), and examined the extent to which K(LEG) predicted K(HAM) in 6 males and 9 females. K(HAM) was moderately consistent day-to-day (ICC(2,5) = .71; SEM = 76.3 N·m(-1)), and 95% limits of agreement (95% LOA) revealed a systematic bias with considerable absolute measurement error (95% LOA = 89.6 ± 224.8 N·m(-1)). Day-to-day differences in procedural factors explained 59.4% of the variance in day-to-day differences in K(HAM). Bilateral and unilateral K(LEG) was more consistent (ICC(2,3) range = .87-.94; SEM range = 1.0-2.91 kN·m(-1)) with lower absolute error (95% LOA bilateral= -2.0 ± 10.3; left leg = -0.36 ± 3.82; right leg = -1.05 ± 3.61 kN·m(-1)). K(LEG) explained 44% of the variance in K(HAM) (P < .01). Findings suggest that procedural factors must be carefully controlled to yield consistent and precise K(HAM) measures. The ease and consistency of K(LEG), and moderate correlation with K(HAM), may steer clinicians toward K(LEG) when measuring lower-extremity stiffness for screening studies and monitoring the effectiveness of training interventions over time.

Evaluation of the effectiveness of anterior cruciate ligament injury prevention programme training components: a systematic review and meta-analysis.

BACKGROUND: Anterior cruciate ligament (ACL) injury prevention programmes have shown mixed results, which may be due to differing emphasis on training components. The purpose of this study was to (1) quantify the overall and relative duration of each training component encompassed within these programmes and (2) examine the effect of these durations on ACL injury rates. METHODS: A systematic review was completed and meta-analyses performed on eligible studies to produce a pooled OR estimate of the effectiveness of these programmes. Meta-regression was used to detect any relationship that programme duration and the duration of individual training components had on ACL injury rates. RESULTS: 13 studies were included for review. Results of the meta-analyses revealed a significant reduction of injuries after preventative training programmes for all ACL injuries (pooled OR estimate of 0.612, 95% CI 0.44 to 0.85; p=0.004) and for non-contact ACL injuries (OR 0.351, 95% CI 0.23 to 0.54; p<0.001). Results of meta-regression analysis revealed that a greater duration of balance training was associated with a higher injury risk for ACL injury (p=0.04), while greater durations of static stretching was associated with a lower injury risk for non-contact ACL injuries (p=0.04). CONCLUSIONS: While ACL prevention programmes are successful in reducing the risk of ACL injury, the ideal combination and emphasis of training components within these programmes remains unclear. Evidence indicates that greater emphases on balance training and static stretching may be associated with an increase and decrease in injury risk, respectively.