Objective: To examine the effects of fatigue on landing biomechanics in single-leg drop landings. Design: Quasi-experimental. Setting: Controlled research laboratory. Participants: Twenty-four healthy individuals (12 women and 12 men). Interventions: Participants performed 3 single-leg drop landings from a height of 0.36 m before and after a fatiguing protocol. Main Outcome Measures: Sagittal ankle flexion, sagittal knee flexion, and frontal knee valgus angles (degrees) at initial ground contact; vertical ground reaction forces (N); and time to stabilization (TTS) were compared between sexes and before (pre) and after (post) the fatiguing protocol. Results: After fatigue, participants landed with greater knee flexion [P = 0.001; pre 142.58 (14.35) degrees; post 136.12 (14.48) degrees] and ankle plantar flexion [P = 0.012; pre 79.04 (6.96) degrees; post 80.78 (6.13) degrees], and higher peak vertical ground reaction forces (P = 0.002; pre 2202.5 (536.29) N to post 2537.86 (469.66) N] but did not show changes in frontal knee angles [P = 0.815; pre, 7.94 (3.74) degrees; post, 8.08 (4.33) degrees]. Participants had higher anterior-posterior TTS [P = 0.021; pre 1.73 (0.53) seconds to post 1.93 (0.53) seconds] and vertical TTS [P = 0.002; pre 0.65 (0.24) seconds to post 0.93 (0.37) seconds] with a significant interaction noted in medial-lateral TTS [P = 0.043; pre 1.49 (0.64) seconds to post 1.61 (0.67) seconds]. No significant sex differences existed across any of the examined variables. Conclusions: When landing after fatigue, participants had greater knee and ankle flexion angles at initial contact, had greater peak ground reaction forces, and required longer times to stabilize the body after landing, regardless of sex. Overall, fatigue clearly affects lower body biomechanics during single-leg landings. Whether these changes actually increase injury risk during activity warrants further investigation.

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° ± 5°) to 50% fatigue (−16° ± 6°) and to 100% fatigue (−14° ± 4°) (F2,34 = 5.112, P = .004). Knee flexion at peak stance increased from prefatigue (−52.9° ± 5.6°) to 50% fatigue (−56.1° ± 7.2°) but decreased from 50% to 100% fatigue (−50.5° ± 7.1°) (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) (F2,34 = 3.755, P = 03). Hip-flexion angle increased from prefatigue (45.4° ± 10.9°) to 50% fatigue (46.2° ± 11.2°) but decreased from 50% to 100% fatigue (40.9° ± 11.3°) (F2,34 = 6.542, P = .004). Hip flexion at peak stance increased from prefatigue (49.8° ± 9.9°) to 50% fatigue (52.9° ± 12.1°) but decreased from 50% to 100% fatigue (46.3° ± 12.9°) (F2,34 = 8.639, P = 001). Hip-abduction angle at initial contact decreased from prefatigue (−13.8° ± 6.6°) to 50% fatigue (−9.1° ± 6.5°) and to 100% fatigue (−7.8° ± 6.5°) (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' 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.

Purpose: Female dancers have lower anterior cruciate ligament (ACL) injury rates compared with physically active women. Enhanced balance can decrease musculoskeletal injury risk. Dancers are proposed to have superior balance compared with physically active nondancers, and this may reduce their risk for ACL injury. However, whether female dancers actually have better balance than active nondancers is unclear. Method: Thirty-three women (15 dancers, 18 nondancers) performed the Balance Error Scoring System (BESS; error scores), the Star Excursion Balance Test (SEBT; percent leg length), and the Modified Bass Test of Dynamic Balance (BASS; maximum score = 100). Results: Dancers had fewer errors on the BESS than did nondancers (p < .001, 12.0 ± 6.9 vs. 25.3 ± 9.1). Dancers also had greater SEBT reach distances in the medial (right, p = .03, 90.4 ± 4.2% vs. 86.5 ± 5.5%; left, p = .04, 90.7 ± 4.5% vs. 86.7 ± 5.9%) and posteromedial directions (right, p = .01, 92.6 ± 5.6% vs. 87.0 ± 6.4%; left, p = .01, 93.9 ± 6.3% vs. 87.9 ± 6.3%), but not in the anteromedial direction (right, p = .23, 84.5 ± 4.4% vs. 86.2 ± 3.5%; left, p = .51, 86.4 ± 3.5% vs. 85.5 ± 4.0%). BASS scores were similar between groups (p = .58, 90.6 ± 5.5 vs. 91.7 ± 56). Conclusions: The novel findings of the study are that dancers had greater balance than did nondancers in some but not all tests. Although dancing may improve balance as compared with not dancing, it is not better than physical activity in improving balance. Thus, balance comparisons between dancers and nondancers may not fully explain why female dancers exhibit low ACL injury rates compared with physically active women. Other factors (e.g., anticipated/unanticipated movement demands) should be examined to understand the ACL injury disparity between dancers and physically active women.

Ings have a single landing, whereas drop jumps include a subsequent jump after initial landing. With the expected ground impact, instant and landing surface suggested to modulate landing neuromechanics, muscle activity, and kinetics should be the same in both tasks when landing from the same height onto the same surface. Although previous researchers have noted some differences between these tasks across separate studies, little research has compared these tasks in the same study. Thus, we examined whether a subsequent movement after initial landing alters muscle activity and kinetics between drop landings and jumps. Fifteen women performed 10 drop landings and drop jumps each from 45 cm. Muscle onsets and integrated muscle activation amplitudes 150 milliseconds before (preactivity) and after landing (postactivity) in the medial and lateral quadriceps, hamstrings, and lateral gastrocnemius and peak and time-to-peak vertical ground reaction forces were examined across tasks (p ≤ 0.05). When performing drop jumps, subjects demonstrated later (p = 0.02) gastrocnemius and lesser lateral gastrocnemius (p = 0.002) and medial quadriceps (p = 0.02) preactivity followed by increased postactivity in all muscles (p = 0.006), with higher peak vertical ground reaction forces (p = 0.04) but no differences in times to these peaks (p = 0.60) than drop landings. The later gastrocnemius activation, higher gastrocnemius and quadriceps postlanding amplitudes, and higher ground reaction forces in drop jumps may allow subjects to propel the body vertically after the initial landing vs. simply absorbing impact in drop landings. Our results indicate that in addition to landing surface and height, anticipation of a subsequent task changes landing neuromechanics. Generalizations of results from landing-only studies should not be made with landing followed-by-subsequent-activity studies. Landing exercises should be incorporated based on sport-specific demands....