The effect of plantarflexion angle on landing mechanics using a within-subjects real-time feedback protocol

Rowley, Michael
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University of Delaware
The mechanics of landing play an important role in the ground reaction forces, joint forces, and joint moments thought to lead to injury in sport. The ankle joint’s role in shock absorption has been researched in many studies. Within-subject and between subjects studies have found that landing with higher amounts of plantarflexion (PF) results in lower peak ground reaction forces (GRFs).⁹,¹⁸ There has not yet been a study that compares drop landings within-subjects along a quantitative continuum of PF angles. Subjects were asked to land at a self-selected ankle angle for three trials. Next, using a custom-written real-time feedback program, subjects adjusted their ankles to an instructed angle – between 0° (dorsiflexed) and 50° (plantarflexed) degrees – and dropped onto two force platforms. For increasing PF, peak GRF and peak loading rate decreased significantly. The peak support moment, defined as the sum of the extensor moments in the ankle, knee, and hip²³, also decreased with increasing PF angle. In dorsiflexed landings, the hip and knee were in a more flexed position at landing, and in plantarflexed landings, they were more extended at landing. The hip’s contribution to peak total support moment decreased between dorsiflexed landings to 30° plantarflexed landings while the ankle and knee contributions increased between 0° to 30° landings. There appears to be no optimal PF angle to reduce peak GRF and loading rate, but there may be an optimum where joint contributions converge and the hip moment contribution is minimized.