Prediction of Dynamic Postural Stability During Single-Leg Jump Landings by Ankle and Knee Flexibility and Strength.

CONTEXT: Dynamic postural stability is important for injury prevention, but little is known about how lower-extremity musculoskeletal characteristics (range of motion [ROM] and strength) contribute to dynamic postural stability. Knowing which modifiable physical characteristics predict dynamic postural stability can help direct rehabilitation and injury-prevention programs. OBJECTIVE: To determine if trunk, hip, knee, and ankle flexibility and strength variables are significant predictors of dynamic postural stability during single-leg jump landings. DESIGN: Cross-sectional study. SETTING: Laboratory. PARTICIPANTS: 94 male soldiers (age 28.2 ± 6.2 y, height 176.5 ± 2.6 cm, weight 83.7 ± 26.0 kg). INTERVENTION: None. MAIN OUTCOME MEASURES: Ankle-dorsiflexion and plantar-flexion ROM were assessed with a goniometer. Trunk, hip, knee, and ankle strength were assessed with an isokinetic dynamometer or handheld dynamometer. The Dynamic Postural Stability Index (DPSI) was used to quantify postural stability. Simple linear and backward stepwise-regression analyses were used to identify which physical characteristic variables were significant predictors of DPSI. RESULTS: Simple linear-regression analysis revealed that individually, no variables were significant predictors of the DPSI. Stepwise backward-regression analysis revealed that ankle-dorsiflexion flexibility, ankle-inversion and -eversion strength, and knee-flexion and -extension strength were significant predictors of the DPSI (R2 = .19, P = .0016, adjusted R2 = .15). CONCLUSION: Ankle-dorsiflexion ROM, ankle-inversion and -eversion strength, and knee-flexion and -extension strength were identified as significant predictors of dynamic postural stability, explaining a small amount of the variance in the DPSI.

Musculoskeletal, biomechanical, and physiological gender differences in the US military.

UNLABELLED: The repeal of the Direct Ground Combat Assignment Rule has renewed focus on examining performance capabilities of female military personnel and their ability to occupy previously restricted military occupational specialties. Previous research has revealed female Soldiers suffer a greater proportion of musculoskeletal injuries compared to males, including a significantly higher proportion of lower extremity, knee, and overuse injuries. Potential differences may also exist in musculoskeletal, biomechanical, and physiological characteristics between male and female Soldiers requiring implementation of gender-specific training in order to mitigate injury risk and enhance performance. PURPOSE: To examine differences in musculoskeletal, biomechanical, and physiological characteristics in male and female Soldiers. METHODS: A total of 406 101st Airborne Division (Air Assault) Soldiers (348 male; 58 female) participated. Subjects underwent testing for flexibility, isokinetic and isometric strength (percent body weight), single-leg balance, lower body biomechanics during a stop jump and drop landing, body composition, anaerobic power/capacity, and aerobic capacity. Independent t tests assessed between-group comparisons. RESULTS: Women demonstrated significantly greater flexibility (P<.01-P<.001) and better balance (P≤.001) than men. Men demonstrated significantly greater strength (P≤.001), aerobic capacity (47.5±7.6 vs 40.3±5.4 ml/kg/min, P<.001), anaerobic power (13.3±2.1 vs 9.5±1.7 W/kg, P<.001), and anaerobic capacity (7.8±1.0 vs 6.1±0.8 W/kg, P<.001) and lower body fat (20.1±7.5 vs 26.7±5.7 (%BF), P<.001). Women demonstrated significantly greater hip flexion and knee valgus at initial contact during both the stop jump and drop landing tasks and greater knee flexion at initial contact during the drop landing task (P<.05-P<.001). CONCLUSIONS: Gender differences exist in biomechanical, musculoskeletal, and physiological characteristics. Sex-specific interventions may aid in improving such characteristics to optimize physical readiness and decrease the injury risk during gender-neutral training, and decreasing between-sex variability in performance characteristics may result in enhanced overall unit readiness. Identification of sex-specific differences in injury patterns and characteristics should facilitate adjustments in training in order for both sexes to meet the gender-neutral occupational demands for physically demanding military occupational specialties.