By failing to prepare, you are preparing your anterior cruciate ligament to fail

Abstract

There is strong evidence linking an athlete's movement technique during sidestepping with anterior cruciate ligament (ACL) injury risk. However, it is unclear how these injurious postures are influenced by prior movement. We aim to describe preparatory trunk and thigh kinematics at toe‐off of the penultimate‐step and flight‐phase angular momenta, and explore their associations with frontal‐plane risk factors during unplanned sidestepping maneuvers. We analyzed kinematic and kinetic data of 33 male Australian Football players performing unplanned sidestepping tasks (103 trials). Linear mixed models tested for reliable associations between ACL injury risk during weight acceptance of the execution‐step, with preparatory kinematics and angular momenta of the trunk and thigh during the penultimate‐step. Multi‐planar flight‐phase trunk momenta along with hip abduction angle at penultimate‐step toe‐off were significantly associated with peak knee valgus moments during the execution‐step (R2 = .21, P < .01). Execution‐step trunk lateral flexion was significantly predicted by frontal and sagittal‐plane preparatory trunk positioning at toe‐off of the penultimate‐step (R2 = .44, P < .01). Multi‐planar flight‐phase trunk momenta as well as multi‐planar trunk and hip positioning at penultimate‐step toe‐off were associated with hip abduction during the execution‐step (R2 = .53, P < .01). Preparatory positioning of the trunk and hip, along with flight‐phase trunk momentum adjusting this positioning are linked to known ACL injury risk factors. We recommend that during the penultimate‐step athletes maintain an upright trunk, as well as minimize frontal‐plane trunk momentum and transverse‐plane trunk momentum toward the sidestep direction to reduce risk of ACL injury during unplanned sidesteps.

Fatigue Induced by Repeated Changes of Direction in Élite Female Football (Soccer) Players: Impact on Lower Limb Biomechanics and Implications for ACL Injury Prevention

“…In addition, the higher CoM approach speed influences body momentum and thus the loads absorbed during the CoD. As the average shuttle speed had to be maintained constant, we hypothesize this might be due to a reduced braking contribution in the penultimate step ( Jones et al, 2016a ; David et al, 2018 ; Dos’Santos et al, 2020 ; Staynor et al, 2020 ). A plausible motivation of lower knee and hip flexion could be that fatigued muscles ([La – ] b > 11 mmol/L) might have become progressively less effective in dissipating impact forces through eccentric action, thus transmitting load to passive structures ( Alentorn-Geli et al, 2009 ; Cortes et al, 2013 ; Weiss and Whatman, 2015 ; Zago et al, 2019 ).…”

“…However, our initial hypothesis by which fatigue induced by repeated CoDs over a short timescale (minutes) can potentially generate hazardous alterations in lower limbs biomechanics was supported in a subset of the assessed cohort. For those players, the identified changes at initial contact were reported to increase the risk of ACL injury ( Weiss and Whatman, 2015 ; Staynor et al, 2020 ), dangerously bringing an athlete closer to the so called “position of no return” ( Hilibrand et al, 2015 ). While this was not a univocal effect, we believe that it cannot be ignored: testing in fatigued conditions should be considered for screening purposes and to properly evaluate an athlete’s neuromuscular control ( Smeets et al, 2020 ; Verschueren et al, 2020 ).…”

“…Positive (negative) correlation means that the angle increased (decreased) throughout the exercise, toward the direction indicated by the "±" symbols; for example, a negative correlation in hip flexion angle indicates a progressive reduction of the hip flexion angle during the test. Staynor et al, 2020). A plausible motivation of lower knee and hip flexion could be that fatigued muscles ([La − ] b > 11 mmol/L) might have become progressively less effective in dissipating impact forces through eccentric action, thus transmitting load to passive structures (Alentorn-Geli et al, 2009;Cortes et al, 2013;Weiss and Whatman, 2015;Zago et al, 2019).…”

Is There a Sex Difference in Trunk Neuromuscular Control among Recreational Athletes during Cutting Maneuvers?

“…Trunk kinematics and neuromuscular control were influenced by the cutting angle. More specifically, directed co-contraction ratios were only altered during the pre-activation phase, which underlines the importance of the preparatory phase during cutting maneuvers (Dos'Santos et al, 2019;Mornieux et al, 2014;Staynor et al, 2020). Although trunk flexion increased at the sharper cutting angle, the reduced co-contraction prior to foot contact for trunk flexors during 60° compared to 30° COD might indicate that participants tried to avoid leaning forward too much.…”

The effect of planning time on penultimate and ultimate step kinematics and subsequent knee moments during sidestepping

“…Previous research has shown that when there is increased rotation and lateral flexion of the trunk away from the sidestepping direction, at ultimate step IFC, the GRF vector is directed more lateral to the knee joint center, and the COM trajectory initially progresses toward the stance foot before the body changes direction 10 . Staynor et al 34 suggest that when frontal plane trunk momentum is directed toward the stance limb in the ultimate step, a wider stance foot placement (as represented in this study by hip abduction angle) is likely necessary to successfully execute a sidestep 34 . A wider mediolateral foot placement, as seen in upSS, has the potential to increase the frontal plane moment arm of the GRF, increasing the capacity of the GRF to generate externally applied knee valgus moment 35 .…”