Background and Rationale

The decision of when patients should return to activity following anterior cruciate ligament reconstruction (ACLR) is a complex process and there is a lack of consistency in the criteria used to inform return to activity recommendations. Postural control is an important factor to acknowledge for ACLR patients throughout their recovery. Postural control consists of postural orientation and postural stability, and emerges from the interaction between individuals, tasks, and the surrounding environment.1 All motor tasks require postural control.

Postural stability is processed unconsciously; however, assessments of postural stability often focus on the conscious control of posture, as opposed to the automatic (unconscious) response of the body to maintain its upright posture during athletic activities.2 To address these limitations, dual task paradigms are usually employed to better assess the automatic nature of postural stability.3 Dual task assessments commonly involve maintaining an upright posture (single task) while employing a second task (motor, visual, or cognitive).

Postural stability can be assessed both statically and dynamically, although dynamic postural stability may be more suitable to assess following ACLR, as the majority of non-contact ACL injuries occur during landing or cutting movements.4 Several studies have investigated participant postural control with added cognitive tasks.2,3,5,6 However, our recent scoping review highlighted limited work concerning the assessment of dynamic postural stability with dual tasks in post-ACLR patients.7 This evidence gap impairs clinician and patient decision-making, as it is unknown how postural stability in the affected limb of post-ACLR patients may differ from their unaffected side during a dynamic athletic task, and how postural stability in post-ACLR patients might be altered when completing an athletic task with an added cognitive task. Additionally, there is a paucity of research examining how postural stability in post-ACLR patients compares to a cohort of healthy participants in both single and dual-task conditions. Our sub-protocol will address the identified limitations of previous literature using different jump tasks.

Hypothesis

We hypothesize that post-ACLR individuals will demonstrate differences in dynamic postural stability as compared to healthy individuals, as measured by time to stabilization (TTS), center of pressure (CoP) displacement, CoP length of path, CoP velocity, and the dynamic postural stability index (DPSI). Due to reported differences in cortical activity immediately after landing in individuals with and without ACLR,8 we hypothesize that the addition of a cognitive task (Stroop test) to a motor task (countermovement jump) will further challenge dynamic postural stability. The addition of the added task to the countermovement jump will affect dynamic postural stability (i.e., increase TTS), but, to a lesser degree in the healthy participants as compared to the participants who have undergone ACLR.