The effect of ankle bracing and range of motion on landing biomechanics in young netballers
Introduction Lower extremity injury is common in netball. Reduced ankle dorsiflexion range of motion has been linked to a number of these injuries although the biomechanical reasons for the association are as yet unclear. Ankle injury is particularly common in netball and netballers are encouraged to wear ankle braces to reduce the risk of ankle injury. These braces have the potential to predispose athletes to injury further up the kinetic chain as research has shown braces can restrict ankle dorsiflexion range of motion. The aims of this thesis were to investigate in young netballers: 1) The effect of restricted ankle dorsiflexion range of motion on landing biomechanics and 2) The effect of ankle bracing on landing biomechanics.
Methods Landing biomechanics were investigated during a drop jump, drop land, and a netball-specific task involving a pass and a one-to-two landing style (unilateral initial landing with the second foot quickly brought down ahead of the first). Dependent variables included leg, knee and ankle stiffness, knee/ankle stiffness ratio, knee and ankle sagittal excursion, peak vertical ground reaction force (vGRF), time-to-peak vertical ground reaction force (TTP), and loading rate (LR) during landing. These variables were investigated using 3D motion capture and force plates. To investigate the association between dorsiflexion range of motion and landing biomechanics participants were divided into high and low dorsiflexion groups and results compared between groups. A within-subject design was used to investigate the effect of lace-up ankle braces with participants performing all tasks with and without braces.
Results Ankle stiffness was moderately higher in the low DF group on the left during the drop land (ES=0.84) and in the lead limb during the netball jump (ES=0.87). The low DF group also had moderate reduction in ankle excursion on the left during the drop jump (ES=-0.55) and in the trailing ankle during the netball jump (ES=-0.97). Additionally they showed a large increase in knee excursion on the left during the drop jump (ES=1.91) and in the trailing limb during the netball jump (ES=1.85).
In the brace condition there was a small increase in bilateral leg stiffness during the drop land (ES=0.21, 0.22), a small increase in bilateral ankle stiffness during the drop jump (ES=0.37, 0.29), a small to moderate increase in bilateral ankle stiffness during the drop land (ES=0.40, 0.60), and small reductions in the knee/ankle stiffness ratio in all three tasks (ES=-0.22 to -0.45). Additionally, in the brace condition there were small decreases in bilateral ankle sagittal excursion during the drop jump (ES=-0.35,-0.53) and drop land (ES=-0.23,-46) and in the lead limb during the netball jump (ES=-0.36). Finally, in the brace condition there was a small reduction in knee excursion bilaterally during the drop jump (ES=-0.36,-0.40) and in the lead limb during netball task (ES=-0.59), and a small increase in lead limb TTP during the netball jump (ES=0.41).
Conclusion Young netballers with low DF ROM may exhibit greater ankle stiffness, less ankle sagittal excursion and more sagittal knee excursion during landing than netballers with greater range. Lace-up ankle braces may result in greater leg and joint stiffness and reduced joint excursion during landing but do not appear to affect landing forces. These biomechanical changes may predispose young netballers to lower extremity injury and should be considered in the training and long term use of ankle braces in this group.