I review this paper in my Research Review this week, although the study itself doesn’t prescribe interventions – we have been using Posterior chain strength in all our rehabilitation programs over the past 24 months with great effect – Compound lifts where possible – certainly not isometric or body weight holds or mobility work!
Female athletes are more likely to suffer a noncontact anterior cruciate ligament (ACL) injury during sports compared with male. Studies suggest that females exhibit movement and loading patterns that place them at a greater risk for ACL injury. Some of these patterns, such as greater peak external knee abduction moments and peak abduction angles, prospectively predict ACL injury risk in female athletes. Despite the considerable amount of evidence that implicate movement and loading patterns as part of the noncontact ACL injury mechanism, it is not well understood how other aspects such as central processing, environment, and physical abilities influence biomechanical patterns during movement tasks.
Experimental paradigms that use unanticipated tasks to study lower extremity kinematics and kinetics may provide better insight into movement and loading patterns that athletes would encounter during competition. When compared with anticipated tasks, lower extremity biomechanics during unanticipated tasks are consistent with kinematic and kinetic profiles known to increase the risk of ACL injury. The use of unanticipated landing paradigms may therefore offer better insights into possible “worst-case scenarios” of lower extremity movement and loading patterns that one could expect to experience during a practice or game situation.
In addition, it is important to gain an understanding of the influence of trainable physical abilities (e.g., muscular strength) on the lower extremity biomechanics during movement tasks, especially those tasks that are performed under time-critical situations. Although existing studies provide collective support for the hypothesis that hip muscle strength affects the dynamic control of the lower extremity during athletic movement tasks, it is currently not known to what extent hip strength affects dynamic kinematic and kinetic control during unanticipated single-leg landing and cutting tasks.
The purpose of this study was to determine the influence of hip muscle strength on lower extremity kinematics and kinetics during unanticipated single-leg landing task.
Twenty-three healthy female National Collegiate Athletic Association division I soccer players (19.4 ± 0.8 years, 167.9 ± 5.0 cm, 61.0 ± 4.0 kg) were recruited for this study.
Maximal isometric hip abduction and external rotation torque were measured using a hand-held dynamometer and used as the independent variables for the study. The measurements were expressed as muscle torque (force x femoral length) and normalized to body weight.
Subjects were asked to perform 3 different types of unanticipated single-leg landing tasks that consisted of either a: (a) single-leg land and hold (b) single-leg land and side cut, or (c) single-leg land and forward run. All single-leg landing tasks required subjects to jump off the box and land on the force plate with 1 leg and stabilize their body during the landing without touching the opposite foot to the ground or taking a step. Each subject performed between 3–5 successful trials of each unanticipated single-leg landing and cutting task. The tasks were performed randomly with the use of a custom program that was interfaced with a pressure switch mat placed on the top of the box. Once participants broke contact with the switch mat after jumping off, the program displayed a red light (single-leg land), right arrow (land and side cut), or forward arrow (land and forward run) on a large TV screen in front of the subject.
A 14-camera motion analysis system was used to record kinematic data at a rate of 120 Hz. Kinetic data were collected with an AMTI force plate at 960 Hz. The 3-dimensional positions of 23 retroreflective markers were recorded during each task.
An inverse dynamics approach was used to calculate the net internal joint moments using the ground reaction force data and segmental kinematic data. The variables of interest were the 3-dimensional hip and knee joint angle excursions and peak joint moments during the landing phase of each unanticipated task.
Statistical correlation coefficients were then used to determine the associations between the independent variables (i.e., hip abduction and external rotation torque) and the dependent variables (i.e., hip and knee excursion and peak hip and knee internal joint moments in all planes).
Significant correlations were found between hip external rotator strength and transverse plane joint moments at the hip and knee. Specifically, hip external rotator strength was significantly correlated with the peak hip external rotation moment (r = 0.47; p = 0.021) and peak knee internal rotation moment(r = 0.41; p = 0.048). Frontal plane hip excursion (r = 0.49; p = 0.017) and transverse plane knee excursion (r = 20.56; p = 0.004) were also significantly associated with hip external rotator strength. A statistical trend was also present for the correlation between hip external rotator strength and peak hip abduction moment (r = 0.39; p = 0.06). Hip abductor strength was not significantly correlated with any other biomechanical variables.
The results partially support the hypothesis that greater hip strength would be associated with better lower extremity kinematic and kinetics during unanticipated single-leg landing and cutting tasks. Therefore, practitioners should consider implementing hip muscle strengthening into training programs for athletes who participate in sports that require landing and cutting.
Malloy PJ et al. (2016) Hip external rotator strength is associated with better dynamic control of the lower extremity during landing tasks. J Strength Conditioning Res 30, 282–291.