Biomechanical Profiles When Towing a Sled and Wearing a Weighted Vest Once Cleared for Sports Post–ACL Reconstruction

Abstract

Background:

Though rehabilitation attempts to correct “stiff knee gait” and control for dynamic limb valgus after anterior cruciate ligament reconstruction (ACLR), impaired biomechanics often persist when an individual is cleared to return to sport (RTS). Reduced knee extension moments (KEMs) and knee flexion angles (KFAs) often continue. While at the hip, increased hip adduction angles (HADDAs) and hip internal rotation angles (HIRAs) often persist in spite of dynamic hip stabilization exercises. Sled towing and weighted vest tasks increase KEM and hip extension moments (HEMs) in healthy individuals, yet biomechanical profiles during these tasks after ACLR are unknown.

Hypothesis:

Weighted gait will increase KEM, HEM, hip abduction moments (HABDMs), and hip external rotation moments (HERMs) and will not increase unwanted biomechanics (limb asymmetries, HIRA, HADDA) compared with normal gait.

Study Design:

Controlled laboratory study.

Level of Evidence:

Level 4.

Methods:

Fourteen men and 24 women who were 5 to 12 months after ACLR, had no concomitant ligament injuries, and were cleared to RTS were recruited. Sexes were evaluated independently given the sex-specific incidence to ACL injury, reinjury, and gait responses to certain interventions. Joint moment impulses and peak angles over the first 25% of stance were compared between limbs and across tasks (eg, unweighted gait, sled 50% body weight [BW], and vest 50% BW).

Results:

Men showed that weighted gait increased KEM, HEM, HERM, HADBM (vest only), HADDA, HIRA (sled only), and KFA. Asymmetrical KEM and KFA existed across tasks. Women showed that weighted gait increased KEM, HEM, HERM, HADBM (vest only), HFA (sled only), HADDA, and KFA. Asymmetrical KEM, HEM, HIRA, and KFA (sled only) existed across tasks.

Conclusion:

Weighted gait generally increased joint moments. Unwanted biomechanics were unique for each weighted gait task.

Clinical Relevance:

Though joint moments increased, both tasks created unwanted biomechanics after ACLR. Persistent hip (women only) and KEM asymmetries across tasks when cleared to RTS are concerning given the relationship among these biomechanics and decreased functional performance.