Changes in lower extremity biomechanics due to a short-term fatigue protocol

Abstract

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 sidestepcutting 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 hipand 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 (-178 ± 5°) to 50% fatigue (-168 ± 6°) and to 100% fatigue (-148 ± 4°) (F2,34 = 5.112, P = .004). Knee flexion at peak stance increased from prefatigue (-52.98 ± 5.6°) to 50% fatigue (-56.18 ± 7.2°) but decreased from 50% to 100% fatigue (-50.58 ± 7.1°) (F 2,34 = 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 (45.48 ± 10.9°) to 50% fatigue (46.28 ± 11.2°) but decreased from 50% to 100% fatigue (40.98 ± 11.3°) (F 2,34 = 6.542, P = .004). Hip flexion at peak stance increased from prefatigue (49.88 ± 9.9°) to 50% fatigue (52.98 ± 12.1°) but decreased from 50% to 100% fatigue (46.38 ± 12.9°) (F 2,34 = 8.639, P = 001). Hip-abduction angle at initial contact decreased from prefatigue (-13.88 ± 6.6°) to 50% fatigue (-9.18 ± 6.5°) and to 100% fatigue (-7.88 ± 6.5°) (F 2,34 = 11.228, P