Reviewed By: Evan Peterson PT, DPT
Ankle sprains are one of the most common injuries and occur in a variety of different settings. Whether it is a young athlete or an individual who rolls their ankle by missing a step, many will experience and ankle sprain at least once in their lifetimes. Chronic Ankle Instability or CAI is typically caused by repetitive lateral ankle sprains and can result in articular changes or degenerative osteoarthritis in the ankle. The ankle is an important joint for walking and balance and in order to perform both tasks well, a person must be able to utilize various neuromuscular strategies which include both feedback and feedforward control. In its simplest terms, feedback control is reactive whereas, feedforward control is proactive. Feedback control is our body’s ability to respond to a changing environment and feedforward control is our body’s ability to prepare for an environment we expect. It is proposed that those with CAI have deficits in both feedback and feedforward neuromuscular control. What this means for preventing reoccurring ankle injury is that a person with CAI may have difficulty adjusting their foot and ankle posture to create stability while attempting functional or recreational activities.
Yen et al. 2016 wanted to confirm their belief that people with CAI have impairments in their feedforward and feedback control during walking. Previously, they conducted a similar study testing feedback control of healthy subjects while walking. They found significant increase in ankle positioning (less inversion) while walking due to external loads.
Methods
The authors selected 12 students from Northeastern University who had no significant differences. The subjects filled out a Cumberland Ankle Instability Tool (CAIT) to determine the severity of their recurring ankle sprain. In this study, recurring ankle sprain was defined as at least 2 ankle sprains in the past 6 months. Control subjects scored highly on the CAIT and did not report ankle sprain in the past year. Ankle movement was captured via a motion capture system comprising of 6 cameras. Patients were asked to walk on a treadmill at a self-selected comfortable pace for 3 separate conditions. The first condition acted as a baseline, the second was the intervention phase in which sandbags were placed on the subject’s lateral metatarsal bones, forcing inversion, and the third condition had the bags removed.
Results
The baseline condition showed no significant difference between amount of inversion; however, the CAI group had a trend toward more inversion. During the intervention phase of the trial, both groups showed a change in the amount of eversion over a period of time. The group without CAI had increased eversion throughout the trial whereas the CAI group originally corrected to a more everted position but soon returned to baseline measures. After the weights were removed in the third condition, the increase in ankle eversion carried over in the control group. The CAI group showed a return to baseline suggesting no after effect from the external load.
Discussion
The results show that with external load both the control group and the group with CAI are able to respond to changes in their environment but the CAI group has difficulty doing so for a prolonged amount of time. The authors of this article were unable to identify a specific reason for this occurrence, but were able to formulate a few hypotheses. First is that the individuals were able to detect changes in the environment, but overtime became less sensitive to these changes. A less likely explanation is that the individuals with CAI have decreased everter muscle strength and endurance. These results suggest feedback control is somewhat diminished in those with CAI. The period in which the sandbags were removed was utilizing to assess a person’s ability to rely on feedforward control. The authors believe due to small changes in the after effect further studies should be conducted to determine the quality of feedforward control in those with CAI.
Physical Therapy First
At Physical Therapy First, our therapists are trained to develop exercises and assess a patient’s strategies when balancing or walking. Following ankle sprain or recurring ankle sprains it can be important to practice utilizing your feedback and feedforward controls in order to retrain your ankle and foot musculature for prevention of future ankle sprain. If you are struggling with an ankle that continues to roll with sports or with household tasks, please contact us and we will be happy to assist you.
Reference:
Feedback and Feedforward Control During Walking in Individuals With Chronic Ankle Instability (jospt.org)