The Influence of Interlimb Differences on Anterior Cruciate Ligament Injury Risk Factors in Female Collegiate Soccer Athletes

Female collegiate soccer athletes suffer anterior cruciate ligament (ACL) injuries at a rate of 0.31 per 1000 athlete-exposures, with 67% of injuries expected to be from a non-contact mechanism. As well, previous studies have demonstrated dissimilarity in non-contact ACL injuries relative to dominant and non-dominant legs; with the non-dominant leg being the involved side in 48-67% of reported incidents. The aim of this study was to examine lower extremity neuromechanics relative to leg dominance during an unanticipated sidestep cutting task, with differing states of fatigue and training. Twenty female collegiate soccer players performed three valid trials for both the dominant and non-dominant leg of an unanticipated sidestep cutting task. Three-dimensional kinematics and kinetics were recorded. Participants performed tasks during pre-and post-fatigue states, and partook in a injury prevention intervention, repeating the testing procedure at the cessation. To assess differences in neuromechanical parameters, for experiment I, a multivariate analyses of variance was conducted to assess the effect of leg dominance, and experiments II and III conducted repeated measures analyses of variance to assess the effects of fatigue and training (p\u3c0.05). For experiment I, no significant differences were found between dominant and non-dominant legs, but each leg displayed a unique time occurrence for peak electromyographic activity prior to contact. Experiment II, no differences were found for leg dominance, but fatigue demonstrated significant decreases in gluteus medius activation during pre-contact (pp=0.002). At post-fatigue, there was a significant change in hip flexion at initial contact, and hip and knee flexion at peak knee adduction moment and peak stance

A Functional Agility Short-Term Fatigue Protocol Changes Lower Extremity Mechanics

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 degrees vs. 7.9 ± 6.5 degrees p = 0.011) than pre-fatigue, and a decreased knee flexion angle (-36.6 ± 6.2 degrees vs. -40.0 ± 6.3 degrees, p = 0.003), as well as hip position post-fatigue had decreased hip flexion angle (35.5 ± 8.7 degrees vs. 43.2 ± 9.5 degrees, 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

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

A Feedback Inclusive Neuromuscular Training Program Alters Frontal Plane Kinematics

-Anterior cruciate ligament (ACL) neuromuscular training programs have demonstrated beneficial effects in reducing ACL injuries, yet further evaluation of their effects on biomechanical measures across a sports team season is required to elucidate the specific factors that are modifiable. The purpose of this study was to evaluate the effects of a 10-week off-season neuromuscular training program on lower extremity kinematics. Twelve Division I female soccer players (age: 19.2 ± 0.8 years, height: 1.67 ± 0.1 m, weight: 60.2 ± 6.5 kg) performed unanticipated dynamic trials of a running stop-jump task pretraining and posttraining. Data collection was performed using an 8-camera Vicon system (Los Angeles, CA, USA) and 2 Bertec (Columbus, OH, USA) force plates. The 10-week training program consisted of resistance training 2 times per week and field training, consisting of plyometric, agility, and speed drills, 2 times per week. Repeated measures analyses of variance (ANOVAs) were used to assess the differences between pretraining and posttraining kinetics and kinematics of the hip, knee, and ankle at initial contact (IC), peak knee flexion (PKF), and peak stance. Repeated measures ANOVAs were also used to assess isometric strength differences pretraining and posttraining. The alpha level was set at 0.05 a priori. The training program demonstrated significant increases in left hip extension, left and right hip flexion, and right hip adduction isometric strength. At IC, knee abduction angle moved from an abducted to an adducted position (-1.48 ± 3.65 degrees to 1.46 ± 3.86 degrees, p = 0.007), and hip abduction angle increased (-6.05 +/- 4.63 degrees to -10.34 ± 6.83 degrees, p = 0.007). Hip abduction angle at PKF increased (-2.23 ± 3.40 degrees to 6.01 ± 3.82 degrees, p = 0.002). The maximum knee extension moment achieved at peak stance increased from pretraining to posttraining (2.02 ± 0.32 to 2.38 ± 0.75 N.m.kg-1, p = 0.027). The neuromuscular training program demonstrated a potential positive effect in altering mechanics that influence the risk of incurring an ACL injury

Effects of Drop Height on Drop Jump Performance

Background: Drop jumps (DJ) are commonly implemented in plyometric training programs in an attempt to enhance jump performance. However, it is unknown how different drop heights (DH) affect reactive strength index (RSI), jump height (JH) and ground contact time (GCT). Objectives: The purpose of this study was to assess the effect of various DHs on RSI, JH, and GCT. Methods: Twenty volunteers with a history of plyometric training (Males = 13, Females = 7; age: 22.80 ± 2.69 yr, height: 175.65 ± 11.81 cm, mass: 78.32 ± 13.50 kg) performed DJs from 30 cm (DJ30), 45 cm (DJ45), 60 cm (DJ60), 76 cm (DJ76), and 91 cm (DJ91) and a countermovement jump (0 cm). A 16-camera Vicon system was used to track reflective markers to calculate JH; a Kistler force plate was used to record GCT. RSI was calculated by dividing JH by GCT. RSI and GCT were compared using a 2x5 (sex x DH) mixed factor repeated measures ANOVA, while JH was compared using a 2x6 (sex x DH) repeated measures ANOVA. Results: There were no interactions, but there was a main effect for sex for both JH (M>F) and GCT (F>M). JH demonstrated no main effect for DH: DJ30 (0.49 ± 0.11 m), DJ45 (0.50 ± 0.11 m), DJ60 (0.49 ± 0.12 m), DJ76 (0.50 ± 0.11 m), and DJ91 (0.48 ± 0.12 m). However, GCT showed a main effect where DJ30 (0.36 ± 0.10 s), DJ45 (0.36 ± 0.12 s), and DJ60 (0.37 ± 0.10 s) were not significantly different but were less than DJ76 (0.40 ± 0.12 s) and DJ91 (0.42 ± 0.12 s). Conclusions: Increasing DH beyond 60 cm increased GCT but did not affect JH, resulting in decreased RSI. Therefore, practitioners designing plyometric training programs that implement DJs may utilize DHs up to 60 cm, thereby minimizing GCT without compromising JH