We recently studied the ankle at school and, being a very common injury, one of our case studies involved an inversion ankle sprain. A common problem with inversion ankle sprains is an increased risk of re-spraining the same ankle (1). I became particularly interested in the topic of methods to reduce this risk. It appears that exercises involving the use of wobble boards and other unstable surfaces are quite popular in the treatment of inversion ankle sprains to minimize the risk of future sprains. My initial question was: are exercises done on a stable surface more effective than exercises done on an unstable surface for reducing the risk of a recurrent ankle sprain? Why or why not?
It’s something I first thought about when Ido Portal wrote a Facebook post about how training handstands on an Indo board may be fun, but would not transfer over to handstands on the ground due to the principle of specificity. Since most athletic activities, and even activities we do on a daily basis, are done on a stable surface (except, perhaps, if you live in a place with lots of snow and the snow collapses under your feet as you walk over! This has happened to me more than once this winter), does it make sense to train your ability to stay balanced on an unstable surface? Can that ability transfer over? What does the scientific evidence actually say?
Alas, I did not find any literature directly addressing my initial question so I strived to answer it from a physiological mechanisms point of view. However, as I looked into this more and discussed with my PBT group more, I discovered that there are many other questions that I need to answer first before I can answer this one! For example, someone brought up the point that in both cases, proprioceptors in the lower leg are being stimulated and that those nerves can’t distinguish between whether or not the stimulation is because of the body moving relative to the ground or the ground moving relative to the body. But are proprioceptors the only thing that is involved with balance? How does the role of the brain and motor control come into play? I have much more learning to do before I can answer this.
Also, I realized that answering these questions and many others in one blog post would take way too long so I am going to make a series of blog posts detailing my exploration into this topic.
Here’s the outline of what I’m going to cover over my next few posts:
First, I think that in order to know if stable or unstable surface training is more effective at reducing the risk of recurrent inversion ankle sprains, I need to understand why there is an increased risk in the first place.
Question 1: What are the differences between those who have recurring ankle sprains (functional ankle instability) and those who do not?
Question 2: Why do those differences exist?
Next, I want to know which methods currently used are effective.
Question 3: Which methods are effective at reducing the risk of recurrent ankle sprains in patients who have already had an ankle sprain?
The next question may be a long one…
Question 4: Why are the methods identified in Question 3 effective (i.e. mechanisms of action) and how do they affect the differences identified in Question 1? Also, as a note for myself, I want to look into nonspecific effects of treatment as well. I can understand that nonspecific effects can influence pain and other disease processes (i.e. viable physiological mechanisms), but would they have an influence on the risk of re-spraining your ankle? If so, how? What would be the physiological mechanisms behind that? And to answer this, I probably have to go back to Question 1/2.
Lastly, going back to my initial question,
Question 5: Which method is more effective at reducing the risk of recurrent inversion ankle sprains: balance exercises done a stable surface or an unstable surface? And why?
You might wonder, what is the purpose of asking these questions if we already have effective methods? Simply put, I think that it is important to ask so that we can continue to further refine our methods and make them more effective.
If anyone has resources that may help me answer these questions, feel free to pass them along :). And a special thanks to my PBT group and Jordan Miller for keeping me on my toes as I pondered these questions – I hope you guys continue to question my thinking as I dive in deeper with my next few posts!
1. Martin RL, Davenport TE, Paulseth S, Wukich DK, Godges JJ, Orthopaedic Section American Physical Therapy Association. Ankle stability and movement coordination impairments: ankle ligament sprains. J Orthop Sports Phys Ther. 2013 Sep;43(9):A1–40.