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Context: Risk of anterior cruciate ligament (ACL) injuries in young female athletes increases with age, appearing to peak during maturation. Changes in hip muscle strength and range of motion (ROM) during this time may contribute to altered dynamic movement patterns that are known to increase risk of ACL injuries. Understanding the longitudinal changes in hip strength and ROM is needed to develop appropriate interventions to reduce the risk of ACL injuries. Objective: To examine the longitudinal changes in hip strength and ROM in female youth soccer players. Design: Longitudinal descriptive study. Setting: Field setting. Participants: 14 female youth soccer athletes (14.1 ± 1.1 y, 165.8 ± 5.3 cm, 57.5 ± 9.9 kg) volunteered as part of a multiyear risk factor screening project. Main Outcome Measures: Clinical measures of hip strength and ROM were collected annually over 3 consecutive years. Passive hip internal rotation (IR), external rotation (ER), abduction (ABD), and adduction (ADD) ROM were measured with a digital inclinometer. Isometric hip ABD and extension (EXT) strength were evaluated using a hand-held dynamometer. Separate repeated-measures ANOVAs compared hip strength and ROM values across 3 consecutive years (P < .05). Results: As youth female soccer players increased in age, there were no changes in normalized hip ABD (P = .830) or EXT strength (P = .062) across 3 consecutive years. Longitudinal changes in hip ROM were observed with increases in hip IR (P = .001) and ABD (P < .001), while hip ADD (P = .009) and ER (P < .001) decreased. Conclusions: Anatomical changes at the hip occur as youth female soccer players increase in age. While there are no changes in hip strength, there is an increase in hip IR and ABD ROM with a concomitant decrease in hip ER and ADD ROM. The resulting asymmetries in hip ROM may decrease the activation and force producing capabilities of the hip muscles during dynamic activities, contributing to altered lower extremity mechanics known to increase the risk of ACL injuries. [ABSTRACT FROM AUTHOR]

Context: Epidemiological data demonstrate the need for lower-extremity injury-prevention training. Neuromuscularcontrol (NMC) programs are immediately effective at minimizing lower-extremity injury risk and improving sport-related performance measures. Research investigating lasting effects after an injury-prevention program is limited. Objective: To determine whether dynamic balance, landing mechanics, and hamstring and quadriceps strength could be improved after a 6-wk NMC intervention and maintained for a season. Design: Prospective case series. Setting: Controlled laboratory. Participants: 11 Division I women's basketball players (age 19.40 ± 1.35 y, height 178.05 ± 7.52 cm, mass 72.86 ± 10.70 kg). Interventions: Subjects underwent testing 3 times, completing the Star Excursion Balance Test (SEBT), Landing Error Scoring System (LESS), and isometric strength testing for the hamstrings and quadriceps muscles. Pretest and posttest 1 occurred immediately before and after the intervention, respectively, and posttest 2 at the end of the competitive season, 9 mo after posttest 1. Subjects participated in eighteen 30-min plyometric and NMC-training sessions over a 6-wk period. Main Outcome Measures: The normalized SEBT composite score, normalized peak isometric hamstrings:quadriceps (H:Q) ratio, and the LESS total score. Results: The mean composite reach significantly improved over time (F2,10 = 6.96, P = .005) where both posttest scores were significantly higher than pretest (70.41% ± 4.08%) (posttest 1 73.48% ± 4.19%, t10 = -3.11, P = .011) and posttest 2 (74.2% ± 4.77%, t10 = -3.78, P = .004). LESS scores significantly improved over time (F2,10 = 6.29, P = .009). The pretest LESS score (7.30 ± 3.40) was higher than posttest 1 (4.9 ± 1.20, t10 = 2.71, P = .024) and posttest 2 (5.44 ± 1.83, t10 = 2.58, P = .030). There were no statistically significant differences (P > .05) over time for the H:Q ratio when averaging both legs (F2,10 = 0.83, P = .45). Conclusions: A 6-wk NMC program improved landing mechanics and dynamic balance over a 9-mo period in women's basketball players. NMC adaptations can be retained without an in-season maintenance program. [ABSTRACT FROM AUTHOR]

Context: Components of gluteal neuromuscular function, such as strength and corticospinal excitability, could potentially influence alterations in lower extremity biomechanics during jump landing. Objective: To determine the relationship between gluteal muscle strength, gluteal corticospinal excitability, and jump-landing biomechanics in healthy women. Setting: University laboratory. Design: Descriptive laboratory study. Participants: 37 healthy women (21.08 ± 2.15 y, 164.8 ± 5.9 cm, 65.4 ± 12.0 kg). Interventions: Bilateral gluteal strength was assessed through maximal voluntary isometric contractions (MVIC) using an isokinetic dynamometer. Strength was tested in the open chain in prone and side-lying positions for the gluteus maximus and gluteus medius muscles, respectively. Transcranial magnetic stimulation was used to elicit measures of corticospinal excitability. Participants then performed 3 trials of jump landing from a 30-cm box to a distance of 50% of their height, with an immediate rebound to a maximal vertical jump. Each jump-landing trial was video recorded (2-D) and later scored for errors. Main Outcome Measures: MVICs normalized to body mass were used to assess strength in the gluteal muscles of the dominant and nondominant limbs. Corticospinal excitability was assessed by means of active motor threshold (AMT) and motor-evoked potentials (MEP) elicited at 120% of AMT. The Landing Error Scoring System (LESS) was used to evaluate jump-landing biomechanics. Results: A moderate, positive correlation was found between dominant gluteus maximus MEP and LESS scores (r = .562, P = .029). No other significant correlations were observed for MVIC, AMT, or MEP for the gluteus maximus and gluteus medius, regardless of limb. Conclusions: The findings suggest a moderate relationship between dominant gluteus maximus corticospinal excitability and a clinical measure of jump-landing biomechanics. Further research is required to substantiate the findings and expand our understanding of the central nervous system's role in athletic movement. [ABSTRACT FROM AUTHOR]

Context: Arthroscopic partial meniscectomy (APM) after meniscal tear has been widely accepted and associated with quick return to activity. Unfortunately, meniscectomy is associated with risk for knee osteoarthritis, which may be attributed to postsurgical quadriceps weakness. This has important implications, as the quadriceps play a prominent role in knee stabilization and energy attenuation in the lower extremity. Objective: To determine the magnitude of interlimb quadriceps strength deficits in people with unilateral APM by systematically reviewing the current literature. Evidence Acquisition: The Web of Knowledge databases were searched on September 22, 2010, using terms meniscus OR meniscectomy AND quadriceps strength OR quadriceps weakness. Included articles were written in English, reporting means and SDs of isokinetic peak torque at 60° and 180°/s for both limbs. Evidence Synthesis: Four articles were included in the final analysis. Effect sizes and 95% confidence intervals (CI) were calculated between limbs for periods less than 1 mo, 1-3 mo, 3-6 mo, and more than 6 mo. Conclusion: Homogeneous effect sizes indicate quadriceps weakness in the involved limb. Effects were strong at less than 1 mo (d = -1.01 to -1.62), while weak to strong effects were found for 1-3 mo (d = -0.40 to -8.04) and 3-6 mo (d = -0.40 to -5.11). Weak effects were found at more than 6 mo (d = -0.30 to -0.37). Definitive effects with a CI not crossing zero were found in 65% of the data. Although APM patients return to function within weeks after surgery, prolonged quadriceps strength deficits may increase the risk of knee-joint degeneration. Furthermore, evidence of bilateral dysfunction after unilateral injury may suggest that neuromuscular deficits post-APM are greater than the interlimb differences found in this review. Further research should be conducted to determine the nature of strength deficits and the best methods for restoring strength after APM. [ABSTRACT FROM AUTHOR]

PURPOSE: This study aimed to investigate the influence of chronic ankle instability (CAI) on lower extremity joint energy dissipation patterns during a stop-jump task. METHODS: Nineteen participants with self-reported CAI and 19 healthy control participants volunteered. Participants performed five double-leg vertical stop-jump tasks onto a force plate. Lower extremity kinetics and kinematics were examined with an electromagnetic tracking system interfaced with a nonconductive force plate. Lower extremity joint energy dissipations were calculated for the hip, knee, and ankle in the sagittal plane during 50, 100, 150, and 200 ms after initial contact with the force plate. Energy dissipation values were normalized to the product of body mass and height [J·(N·m)]. Individual joint contribution to total lower extremity energy dissipation by the ankle, knee, and hip was reported as the percentage of energy dissipation by each joint over the total energy dissipation of all three joints. Independent t-tests and standard mean differences were conducted to assess differences in each dependent variable between the CAI and the control groups. Significance was set a priori at P < 0.05. RESULTS: The CAI group demonstrated significantly less percentage of knee energy dissipation (P = 0.04) and higher percentage of ankle energy dissipation (P = 0.035) of the total energy dissipation during the 100 ms immediately after initial contact compared with the control group. CONCLUSIONS: We found altered energy dissipation patterns at the knee and ankle during a stop-jump task in the CAI group. These findings may provide insight into kinetic alterations that may be associated with CAI. Future research should consider this information as it may be used to develop more effective interventions to target these potentially modifiable energy dissipation patterns in those with CAI. [ABSTRACT FROM AUTHOR]