Measures of Functional Performance and Their Association With Hip and Thigh Strength

Context: Insufficient hip and thigh strength may increase an athlete\u27s susceptibility to injury. However, screening for strength deficits using isometric and isokinetic instrumentation may not be practical in all clinical scenarios. Objective: To determine if functional performance tests are valid indicators of hip and thigh strength. Design: Descriptive laboratory study. Setting: Research laboratory. Patients or Other Participants: Sixty-two recreationally athletic men (n = 30, age = 21.07 years, height = 173.84 cm, mass = 81.47 kg) and women (n = 32, age = 21.03 years, height = 168.77 cm, mass = 68.22 kg) participants were recruited. Intervention(s): During session 1, we measured isometric peak force and rate of force development for 8 lower extremity muscle groups, followed by an isometric endurance test. During session 2, participants performed functional performance tests. Main Outcome Measure(s): Peak force, rate of force development, fatigue index, hop distance (or height), work (joules), and number of hops performed during the 30-second lateral-hop test were assessed. The r values were squared to calculate r 2. We used Pearson correlations to evaluate the associations between functional performance and strength. Results: In men, the strongest relationship was observed between triple-hop work and hip-adductor peak force (r2 = 50, P ≤ .001). Triple-hop work also was related to hip-adductor (r2 = 38, P ≤ .01) and hip-flexor (r2 = 37, P ≤ .01) rate of force development. For women, the strongest relationships were between single-legged vertical-jump work and knee-flexor peak force (r2 = 0.44, P ≤ .01) and single-legged vertical-jump height and knee-flexor peak force (r2 = 0.42, P ≤ .01). Single-legged vertical-jump height also was related to knee-flexor rate of force development (r2 = 0.49, P ≤ .001). The 30-second lateral-hop test did not account for a significant portion of the variance in strength endurance. Conclusions: Hop tests alone did not provide clinicians with enough information to make evidence-based decisions about lower extremity strength in isolated muscle groups

Changes in Lower Extremity Biomechanics Due to a Short-Term Fatigue Protocol

Context: Noncontact anterior cruciate ligament injury has been reported to occur during the later stages of a game when fatigue is most likely present. Few researchers have focused on progressive changes in lower extremity biomechanics that occur throughout fatiguing. Objective: To evaluate the effects of a sequential fatigue protocol on lower extremity biomechanics during a sidestep-cutting task (SS). Design: Controlled laboratory study. Setting: Laboratory. Patients or Other Participants: Eighteen uninjured female collegiate soccer players (age 19.2 ± 0.9 years, height = 1.66 ± 0.5 m, mass 61.6 ± 5.1 kg) volunteered. Intervention(s): The independent variable was fatigue level, with 3 levels (prefatigue, 50% fatigue, and 100% fatigue). Using 3-dimensional motion capture, we assessed lower extremity biomechanics during the SS. Participants alternated between a fatigue protocol that solicited different muscle groups and mimicked actual sport situations and unanticipated SS trials. The process was repeated until fatigue was attained. Main Outcome Measure(s): Dependent variables were hip- and knee-flexion and abduction angles and internal moments measured at initial contact and peak stance and defined as measures obtained between 0% and 50% of stance phase. Results: Knee-flexion angle decreased from prefatigue (-17 degrees ± 5 degrees) to 50% fatigue (-16 degrees ± 6 degrees) and to 100% fatigue (-14 degrees ± 4 degrees) (F2,34 = 5.112, P = .004). Knee flexion at peak stance increased from prefatigue (-52.9 degrees ± 5.6 degrees) to 50% fatigue (-56.1 degrees ± 7.2 degrees) but decreased from 50% to 100% fatigue (-50.5 degrees ± 7.1 degrees) (F2,34 = 8.282, P = 001). Knee-adduction moment at peak stance increased from prefatigue (0.49 ± 0.23 Nm/kgm) to 50% fatigue (0.55 ± 0.25 Nm/kgm) but decreased from 50% to 100% fatigue (0.37 ± 0.24) (F 2,34 = 3.755, P = 03). Hip-flexion angle increased from prefatigue (45.4 degrees ± 10.9 degrees) to 50% fatigue (46.2 degrees ± 11.2 degrees) but decreased from 50% to 100% fatigue (40.9 degrees ± 11.3 degrees) (F2,34 = 6.542, P= .004). Hip flexion at peak stance increased from prefatigue (49.8 degrees ± 9.9 degrees) to 50% fatigue (52.9 degrees ± 12.1 degrees) but decreased from 50% to 100% fatigue (46.3 degrees ± 12.9 degrees) (F 2,34 = 8.639, P = 001). Hip-abduction angle at initial contact decreased from prefatigue (-13.8 degrees ± 6.6 degrees) to 50% fatigue (-9.1 degrees ± 6.5 degrees) and to 100% fatigue (-7.8 degrees ± 6.5 degrees) (F2,34 = 11.228, P = .001). Hip-adduction moment decreased from prefatigue (0.14 ± 0.13 Nm/kgm) to 50% fatigue (0.08 ± 0.13 Nm/kgm) and to 100% fatigue (0.06 ± 0.05 Nm/ kg) (F2,34 = 5.767, P = .007). Conclusions: The detrimental effects of fatigue on sagittal and frontal mechanics of the hip and knee were visible at 50% of the participants\u27 maximal fatigue and became more marked at 100% fatigue. Anterior cruciate ligament injury-prevention programs should emphasize feedback on proper mechanics throughout an entire practice and not only at the beginning of practice