Lower Extremity Muscle Contributions to ACL Loading in Healthy and ACL-Reconstructed Females

Females are 16 times greater to sustain a second ACL injury compared to their healthy female counterparts. Many of these females return to play their respective sport after an ACL-reconstruction (ACLR). However, little is known about the influence fatigue in sport has on lower extremity mechanics of ACLR females. The purpose of this study was to investigate the influence muscular fatigue may have on lower extremity mechanics in healthy and ACLR females. It was hypothesized that 1) healthy control and ACLR females would demonstrate different hip, knee, and ankle mechanics, regardless of fatigue, 2) fatigue would influence hip, knee, and ankle mechanics, regardless of previous surgical intervention and 3) there would be an interaction between fatigue and previous surgical intervention. Seven healthy and four ACLR recreationally active females completed five anticipated land-and-cutting trials to the right pre- and post- a fatigue protocol. Three-dimensional lower extremity kinematic and kinetic variables were measured using a motion capture system and force plate. One-dimensional statistical non-parametric mapping were used to assess changes in lower extremity mechanics between healthy control and ACLR females over the entire stance phase. The only group ´ fatigue interaction found was hip flexion angle. Significant group main effects included hip flexion, abduction, and rotation angles. Significant fatigue main effects included hip flexion and knee abduction angles, as well as hip rotation moment. Hip and knee mechanics appear to be influenced by both fatigue and prior ACL surgery. However, hip mechanics seemed to be the most affected by prior ACL surgery, with fatigue being second. Therefore, future research is warranted to investigate the relationship between hip mechanics and ACLR

Effects of Pitch Repetition On Knee Joint Kinetics in Collegiate Baseball Pitchers

Current baseball pitching research has focused primarily on pitcher upper extremity kinematics and kinetics. However, pitching is a full body motion where the stride leg forms a closed kinetic chain that stabilizes the pitcher as they land down the pitching mound and serves as an anchor for the pitcher to pivot around. This single-leg landing motion can occur up to 100 times per game. As such, pitchers may be susceptible to stride knee musculoskeletal injury risk. According to current statistics, 17% of pitcher injuries occur in the lower extremities. Therefore, the purpose of this study was to assess the effects of pitch repetition on 3D stride knee angles and moments in collegiate baseball pitchers. 3D stride knee angles and moments were measured during the first and last inning pitched in a simulated pitching outing. No significant change occurred in 3D stride knee angles and moments from the first inning pitched to the last inning pitched. Our findings suggest that pitch repetition may not affect 3D stride knee angles and moments, therefore may not be a primary mechanism for knee joint injury

Task but not arm restriction influences lower extremity joint mechanics during bilateral landings

Box and jump landing tasks are commonly used to study lower extremity injury mechanisms, such as anterior cruciate ligament (ACL) injuries. Arm restriction during these tasks is typically determined via researcher preference. Therefore, the purpose of this study was to compare three-dimensional lower extremity kinematics and kinetics during bilateral box and jump landings, and to determine the effects of arm restriction. Twenty-eight participants (14 males, 14 females) completed three bilateral landings tasks: box landings with arms unrestricted (BLA), box landings with arms restricted against the trunk (BLNA) and jump landings (JL). Right leg joint kinematics and kinetics were collected and compared between landing tasks. No statistically significant differences were found between BLA and BLNA, therefore arm restriction did not appear to influence lower extremity variables during bilateral box landings. However, specific injury-related variables, such as peak knee adduction moment differed between box and jump landings (BLNA: 0.31 ± 0.3 Nm/(kg·m)); JL: 0.45 ± 0.3 Nm/(kg·m); p = 0.020). Our results suggest that based on study purpose, careful consideration is needed when determining what bilateral landing task to choose during data collection

Lower extremity muscle contributions to ACL loading during a stop-jump task

Landing is considered a high-risk movement, especially landings from a stop-jump task, as they are often associated with lower extremity injuries, such as anterior cruciate ligament injuries (ACL). Females demonstrate lower extremity landing mechanics that often place them at a larger risk of injury compared to their male counterparts. While efforts have been made to understand lower extremity mechanics during stop-jump landings, little is known regarding the musculature function during these tasks and how they may influence ACL loading. Understanding lower extremity muscle contributions to ACL loading (FACL) may give insight to improving injury prevention protocols. Ten healthy, recreationally active females completed five trials of an unanticipated stop-jump task. Right leg kinematics, kinetics, and electromyography data were collected with three-dimensional motion capture, force plates, and electromyography sensors, respectively. Modified musculoskeletal models were scaled based on participant-specific anthropometrics, and muscle forces were obtained using static optimization. An induced acceleration analysis combined with a previously established mathematical ACL loading model was used to calculate lower extremity muscle contribution to FACL. The vastus lateralis, vastus intermedius, vastus medials, biceps femoris long head, semimembranosus, and soleus were found to be the primary contributors to FACL, with the vastus lateralis being the largest contributor. These data suggest that muscles traditionally known as ACL unloaders may in certain conditions load the ACL. These results also suggest that future injury prevention protocols should target muscles specifically to mitigate the influence the vastus lateralis has on ACL loading

Effects of Foot Progression Angle On Knee Mechanics During an Anticipated Cutting Task: A Statistical Parametric Mapping Approach

Cutting is considered a “high-risk” movement for anterior cruciate ligament (ACL) injuries. It has been established that sex differences exist during cutting, placing females at greater ACL injury risk. Foot progression angle (FPA) during landing has been shown to influence lower extremity mechanics, yet little is known how FPA influences mechanics during cutting. The purpose of this study was to compare two FPA conditions during cutting between males and females. Twenty-four males and females were tested using two FPA conditions: toe-in 15° (TI15) and toe-out 15° (TO15). Right knee joint kinematic and kinetic variables were measured using a motion capture system and force plate. Five successful trials were collected and compared between FPA conditions. One-dimensional statistical parametric mapping was used to assess changes in knee mechanics between males and females over the entire stance phase. The only sex × FPA effect found was knee flexion angle. Females cutting at TI15 had decreased knee flexion angle compared TO15 (p = 0.019). Significant sex main effects included knee abduction and rotation angles, and knee flexion and rotation moments. Significant FPA main effects included knee flexion, abduction and rotation angles. The results show cutting with a toe-in FPA of 15° is enough to induce changes in knee abduction angle while cutting with 15° toe-out FPA influenced knee flexion and rotation angles. These data suggest that different cutting FPAs may be influential on known ACL injury risk variables. However, more research is warranted on cutting FPA before FPA is targeted as part of ACL injury prevention protocols

Type of unanticipated stimulus affects lower extremity kinematics and kinetics during sidestepping

Including an unanticipated stimulus has significant impacts on lower extremity biomechanics during dynamic movements. It is unknown how a live, human defender affects lower extremity biomechanics. The purpose of this study was thus to determine the effects of two types of unanticipated stimuli (visual stimulus; defensive opponent) on lower extremity kinematics and kinetics in males and females during 45° sidestepping trials. Eight males and eight females completed two unanticipated stimuli sidestepping conditions. Numeric visual analog scales for reaction difficulty and movement realism were collected and analysed using a 2 × 2 mixed-model ANOVA. Three-dimensional hip, knee, and ankle kinematics and kinetics were measured during the stance phase of the sidestep and analysed using statistical parametric mapping. Participants reported greater difficulty and less realistic movements with the visual stimulus. Unanticipated stimulus main effects were observed for knee abduction angle, and hip extension and adduction, and knee extension and adduction moments. Sex main effects were observed for hip flexion, hip abduction, and ankle dorsiflexion angles, as well as hip abduction, ankle plantarflexion and ankle eversion moments and vertical ground reaction forces. Participants responded differently to two unanticipated stimuli. Careful consideration should be used when determining the type of unanticipated stimulus used

Comparing anterior cruciate ligament injury risk variables between unanticipated cutting and decelerating tasks

To examine the relationship between anterior cruciate ligament injury risk factors in unanticipated cutting and decelerating. Three-dimensional kinematics and ground reaction forces were collected on 11 females (22 [2] y, 1.67 [0.08] m, and 68.5 [9.8] kg) during 2 unanticipated tasks. Paired samples t tests were performed to compare dependent variables between tasks. Spearman rank correlation coefficients were calculated to analyze the relationship between peak internal knee adduction moment and peak anterior tibial shear force (ASF) during 2 unanticipated tasks. Significantly greater knee abduction angles, peak knee adduction moments, and peak ASFs were observed during cutting (P ≤ .05). A strong positive correlation existed between decelerating ASF and cutting ASF (ρ = .67), while correlations between decelerating knee adduction moment and cutting knee adduction moment and decelerating ASF and cutting knee adduction moment were not significant. In situations where time management is a necessity and only one task can be evaluated, it may be more appropriate to utilize an unanticipated cutting task rather than an unanticipated deceleration task because of the increased knee adduction moment and ASF. These data can help future clinicians in better designing more effective anterior cruciate ligament injury risk screening methods

Comparison of ankle kinematics and ground reaction forces between prospectively injured and uninjured collegiate cross country runners

Biomechanical comparative studies on running-related injuries have included either currently or retrospectively injured runners. The purpose of this study was to prospectively compare ankle joint and ground reaction force variables between collegiate runners who developed injuries during the cross country season and those who did not. Running gait analyses using a motion capture system and force platform were conducted on 19 collegiate runners prior to the start of their cross country season. Ten runners sustained running-related injuries and 9 remained healthy during the course of the season. Strike index, peak loading rate of the vertical ground reaction force, dorsiflexion range of motion (ROM), eversion ROM, peak eversion angle, peak eversion velocity, and eversion duration from the start of the season were compared between injury groups. Ankle eversion ROM and peak eversion velocity were greater in uninjured runners while peak eversion angle was greater in injured runners. Greater ankle eversion ROM and eversion velocity with lower peak eversion angle may be beneficial in reducing injury risk in collegiate runners. The current data may only be applicable to collegiate cross country runners with similar training and racing schedules and threshold magnitudes of ankle kinematic variables to predict injury risk are still unknown

Effects of Foot Rotation on ACL Injury Risk Variables During Drop Landing

Purpose: Landing is considered a “high-risk” movement for anterior cruciate ligament (ACL) injuries. Foot progression angle (FPA) during landing has been shown to influence hip, knee, and ankle mechanics. The purpose of this study was to compare five FPA conditions during drop landings between males and females. Methods: Twenty males and females were tested using five FPA conditions: self-selected, toe-in 15°, toe-in 30°, toe-out 15°, and toe-out 30°. Right hip, knee, and ankle joint kinematics and kinetics were collected using a 12-camera motion capture system and two force plates. Five successful trials were collected and compared between FPA conditions. Results: The main effect for FPA condition was statistically different for initial contact hip flexion, hip abduction, hip internal rotation, knee flexion, knee abduction, knee external rotation, and ankle inversion angles compared to self-selected FPA at P \u3c 0.05. Peak hip extension, hip abduction, knee adduction, knee internal rotation, ankle plantar flexion, and ankle inversion moments were also found to be statistically significant (P \u3c 0.05). Overall, females experienced greater initial knee abduction angle (P = 0.028), hip abduction moment (P = 0.006), knee extension moment (P = 0.033), and knee internal rotation moment (P = 0.044), regardless of FPA condition. Males experienced greater initial contact hip abduction angle (P = 0.0017), regardless of FPA condition. Conclusion: The results suggest that landing with large toe-in FPA will increase the magnitude of ACL injury risk variables, and females demonstrated a greater magnitude in these variables compared to males. Injury prevention programs may seek to target FPA as part of training activities to avoid large FPA toe-in landings

The impact of different cross-training modalities on performance and injury-related variables in high school cross country runners

Paquette, MR, Peel, SA, Smith, RE, Temme, M, and Dwyer, JN. The impact of different cross-training modalities on performance and injury-related variables in high school cross country runners. J Strength Cond Res 32(6): 1745-1753, 2018-There are many different types of aerobic cross-training modalities currently available. It is important to consider the effects that these different modalities have on running performance and injury risks. The purpose of this study was to compare movement quality, running economy (RE) and performance, injury-related biomechanical variables, and hip muscle strength before and after training with different cross-training modalities in high school runners. Thirty-one high school male runners trained for 4 weeks in 1 of 3 cross-training modalities, in addition to a running-only (n = 9) group, for which training sessions replaced 2 easy runs per week: cycling (CYCLE; n = 6), indoor elliptical (n = 7), and outdoor elliptical bike (EBIKE; n = 9). Functional movement screen (FMS), RE, 3,000-m performance, hip kinematics, and hip muscle strength were assessed. Paired t-tests and Cohen\u27s d effect sizes were used to assess mean differences for each variable before and after training within each group. Elliptical bike training was the only modality that improved FMS scores (d = 1.36) and RE before and after training (d = 0.48). All groups showed improvements in 3,000-m performance, but large effects were found only for the CYCLE (d = 1.50) and EBIKE (d = 1.41) groups. Running-only (d = 1.25), CYCLE (d = 1.17), and EBIKE (d = 0.82) groups showed improvements in maximal hip extensor strength. Outdoor cycling and EBIKE cross-training may be the most effective cross-training modalities to incorporate in early season training to improve running performance in high school runners