Yen SC, Corkery M, Donohoe A, Grogan M, Wu YN. Feedback and feedforward control during walking in individuals with chronic ankle instability. J Orthop Sport Phys Ther. 2016. Vol 46 Issue 9, 775-783 DOI: 10.2519/jospt.2016.6403
How many of you have had an ankle sprain? Maybe you’ve had more than one? One reason for the chronic nature of ankle sprains may be related to altered feedback and feedforward mechanisms after the initial injury.
85% of ankle sprains are inversion injuries, meaning the injury occurred on the outside of the ankle with the foot rolled inwards. Afterwards, it is possible for an individual to develop chronic ankle instability (CAI), which is defined as “repetitive bouts of lateral ankle instability resulting in numerous ankle sprains” (Yen et al.)
Why does this happen? The researchers of the study above believe that the feedback and feedforward mechanisms for motor control become altered, causing increased likelihood of individuals to sprain their ankle again. This was shown in this study by monitoring the differences between individuals with and without chronic ankle sprains when an external weight (a small sandbag) was placed on top of the subject’s foot while walking. Those with chronic ankle sprains showed different responses in ankle position during the adaptation (initial) and post adaptation (subsequent) periods after the weight was placed on the foot. The chronic ankle sprain group quickly reverted back to their normal walking pattern after the weight was placed on their foot, possibly making them more susceptible to another sprain. The control group did not revert their walking pattern back to normal once the weight was placed on their foot, instead keeping their foot everted or turned out to accommodate the weight. This suggests a change in the feedback control in the chronic ankle instability group. Additionally after the weight was removed, the chronic ankle instability group did not maintain the altered positioning of the ankle to match the control group. This suggests altered feedforward control.
What contributes to feedback and feedforward motor control? Proprioception or the body’s awareness in space contributes to motor control. Those with chronic ankle instability often have poor awareness of the position of their ankle and the motion occurring at their ankle.
What does this mean for you? Individuals who have had one ankle sprain may have altered proprioception during normal activities and sport, making them more susceptible for a second sprain.
What can you do to prevent another sprain? You can work with a physical therapist on improving your ankle proprioception through dynamic and static balance exercises, progressively challenging your ankle as your proprioception improves.