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 ¼ 19.2 6 0.9 years, height ¼ 1.66 6 0.5 m, mass ¼ 61.6 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 (À178 6 58) to 50% fatigue (À168 6 68) and to 100% fatigue (À148 6 48) (F 2,34 ¼ 5.112, P ¼ .004). Knee flexion at peak stance increased from prefatigue (À52.98 6 5.68) to 50% fatigue (À56.18 6 7.28) but decreased from 50% to 100% fatigue (À50.58 6 7.18) (F 2,34 ¼ 8.282, P ¼ 001). Knee-adduction moment at peak stance increased from prefatigue (0.49 6 0.23 Nm/kgm) to 50% fatigue (0.55 6 0.25 Nm/kgm) but decreased from 50% to 100% fatigue (0.37 6 0.24) (F 2,34 ¼ 3.755, P ¼ 03). Hip-flexion angle increased from prefatigue (45.48 6 10.98) to 50% fatigue (46.28 6 11.28) but decreased from 50% to 100% fatigue (40.98 6 11.38) (F 2,34 ¼ 6.542, P ¼ .004). Hip flexion at peak stance increased from prefatigue (49.88 6 9.98) to 50% fatigue (52.98 6 12.18) but decreased from 50% to 100% fatigue (46.38 6 12.98) (F 2,34 ¼ 8.639, P ¼ 001). Hip-abduction angle at initial contact decreased from prefatigue (À13.88 6 6.68) to 50% fatigue (À9.18 6 6.58) and to 100% fatigue (À7.88 6 6.58) (F 2,34 ¼ 11.228, P , .001). Hip-adduction moment decreased from prefatigue (0.14 6 0.13 Nm/kgm) to 50% fatigue (0.08 6 0.13 Nm/kgm) and to 100% fatigue (0.06 6 0.05 Nm/kg) (F 2,34 ¼ 5.767, P ¼ .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.Key Words: anterior cruciate ligament, knee, fatiguing, kinematics, kinetics Key PointsA progressive change in lower extremity mechanics occurred for knee-flexion angle, hip-abduction angle,...

The purpose of this study was to evaluate the effects of a functional agility fatigue protocol on lower extremity biomechanics between two unanticipated tasks (stop-jump and sidestep). The subjects consisted of fifteen female collegiate soccer athletes (19 ± 0.7 years, 1.67 ± 0.1 m, 61.7 ± 8 kg) free of lower extremity injury. Participants performed five trials of stop-jump and sidestep tasks. A functional short-term agility protocol was performed, and immediately following participants repeated the unanticipated running tasks. Lower extremity kinematic and kinetic values were obtained pre and post fatigue. Repeated measures analyses of variance were conducted for each dependent variable with an alpha level set at 0.05. Knee position post-fatigue had increased knee internal rotation (11.4 ± 7.5° vs. 7.9 ± 6.5° p = 0.011) than pre-fatigue, and a decreased knee flexion angle (−36.6 ± 6.2° vs.−40.0 ± 6.3°, p = 0.003), as well as hip position post-fatigue had decreased hip flexion angle (35.5 ± 8.7° vs. 43.2 ± 9.5°, p = 0.002). A quick functional fatigue protocol altered lower extremity mechanics of Division I collegiate soccer athletes during landing tasks. Proper mechanics should be emphasized from the beginning of practice/game to aid in potentially minimizing the effects of fatigue in lower extremity mechanics.

Resistance and plyometric training programs have demonstrated consistent improvements in running economy (RE) in trained and untrained adults in the absence of improvements in maximal oxygen consumption. The purpose of this study was to investigate the effect of a 10-week combined resistance-plyometric training program on the RE and V[Combining Dot Above]O2max in female soccer players. Fifteen Division 1A female soccer players (age 19.0 ± 0.7 years; height 1.67 ± 0.1 m; weight 61.7 ± 8.1 kg) performed a treadmill test for V[Combining Dot Above]O2max and RE at the end of a competitive season (PRE) and after a 10-week training program (POST). Isometric strength was measured in knee flexion and extension. Resistance training was conducted 2 d·wk on nonconsecutive days; plyometric training was conducted separately on different nonconsecutive days. Eleven subjects were included in the PRE-POST analysis (age 19.0 ± 0.8 years; height 1.67 ± 0.5 m; weight 59.9 ± 6.7 kg). Descriptive statistics were compared using analysis of variance with repeated measures with a Bonferroni adjustment, and significance was set at p < 0.05. A significant increase occurred after training in the V[Combining Dot Above]O2peak (10.5%; p = 0.008), time to fatigue (6.9%; p = 0.017), and interpolated maximal speed (3.6%; p = 0.016), despite there being a decrease in the maximal respiratory exchange ratio (2.9%; p = 0.001). There was no significant change in the RE at 9 km·h; however, there was a significant decrease in the percentage of the V[Combining Dot Above]O2peak at 9 km·h (-5.6%; p = 0.02). Maximal isometric strength of knee flexors and extensors did not change. The results suggest a plyometric-agility training program may increase the V[Combining Dot Above]O2peak in female soccer players; however, the effect on RE was equivocal.

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Previous studies have shown conflicting information regarding leg dominance as an etiological factor for the risk of anterior cruciate ligament (ACL) injuries. It remains unclear if lower extremity neuromechanical limb asymmetries exist in experienced athletes. The purpose of this study was to evaluate lower extremity neuromechanical effects of leg dominance in female collegiate soccer athletes during an unanticipated side-step cutting task. Twenty female collegiate soccer players completed an unanticipated side-step cutting task, using their dominant and non-dominant legs. Kinematic and kinetic data were collected to quantify joint angles and forces, with wireless electromyography (EMG) quantifying muscle activity. MANOVA's were conducted to determine the effect of leg dominance on hip and knee mechanics at and between pre-contact, initial contact, peak knee adduction moment, and peak stance periods. Dependent variables consisted of peak time occurrences, hip and knee rotations and moments, ground reaction force, EMG amplitudes, stance time, and approach velocity. No significant differences were found for any variables at or between the periods of interest. Collegiate female soccer athletes exhibit similar movement patterns between dominant and non-dominant legs while performing a side-step cutting task, suggesting that leg dominance does not adversely influence known biomechanical non-contact ACL risk factors.