A growing trend in the fitness industry is the use of unstable surfaces during resistance training. Walk through any local gym or personal training studio and you will see BOSU domes (both sides up), air disks, and balance boards. Some fitness professionals claim that unstable surface training increases balance, proprioception (ability for the body to know where it is and how it is moving), and core stability.
At first glance, it is easy to see why the majority of the population would believe such claims. If you can balance on an unstable surface, why wouldn’t you be able to balance better on a stable surface? If your core is constantly contracting to maintain your center of mass, why wouldn’t your core stability improve? While these claims seem valid, current research does not support these conclusions.
Let’s start by exploring the claim of increased balance. There are few, if any, studies to date that show that the type of increased balance and core stability developed through exercises performed on unstable surfaces transfers to stable surfaces. Therefore, while performing exercises on unstable surfaces may increase an individual’s ability to perform the exercises on that specific surface, it does not necessarily transfer to stable surfaces (ground, grass, court, and even ice). Optimal balance is gained by performing a given task on the surface on which it will be performed in everyday life. Many researchers also believe that performing exercises or sport skills on unstable surfaces could DECREASE the ability to perform the same tasks on a stable surface. As individuals begin to master movement patterns (swinging a bat, bench pressing, squatting, etc.), specific communication pathways between the brain and muscle are created for each movement pattern. When performing the same movement pattern on an unstable surface, it is possible that the individual could interfere with the original pattern created in a stable environment. In addition, since the unstable surface is not specific to the movement being practiced (different surface), the time spent in an unstable environment could have been better spent mastering the movement pattern in a stable environment.
Another popular claim made by proponents of unstable surface training is an increase in core stabilization. As with balance, any core stabilization that is possibly enhanced by activity on an unstable surface has NOT been shown to transfer to stable surfaces. In addition, the ability to provide progressive overload (gradual increases in stress that force adaptation to deal with the stress) is hindered. As an individual increases strength levels, the only way progressive overload can be achieved is either by a further decrease in the surface stability or an increase in resistance. Could you imagine doing a 95 lb. overhead press in Fitness Solutions on a half ball? Most research even shows that performing resistance training exercises on stable surfaces requires MORE core activation and stabilization than performing the SAME exercise on an unstable surface. When performing an exercise on an unstable surface, the weight has to be reduced to such an extent that less overall activation of core musculature occurs. Instead of doing your squat and press with 95 pounds, you would have to do it with 50 pounds while standing on a BOSU ball.
One population that unstable surface training is extremely popular with is athletes. The same issues discussed earlier arise when training athletes on an unstable surface. There is not a significant transfer of skill when you move from performing sport skills (swinging a bat) on unstable surfaces to solid ground. In addition, the time spent performing sport skills on unstable surfaces could be better spent enhancing the same skill on solid ground. Another disadvantage of performing athletic skills on unstable surfaces is the resulting reduction in strength. This reduction in strength is caused by co-contraction of opposing muscles on either side of a joint. For example, when performing a calf raise, the calf muscle is doing the work, while the muscle on your shin is opposing it. When performing a calf raise, you want maximal activation of your calf and minimal activation of your shin muscle. If your shin muscle is significantly active it will reduce the strength you are able to produce with your calf muscle. Simply put, when you perform a calf raise on an unstable surface, you basically confuse the muscles, resulting in less strength (less strength = less speed, less jump height, etc.). This reduction in strength is extremely detrimental to athletic performance.
Based on current research, the use of unstable surfaces outside of a rehabilitative setting (physical therapy) is not recommended. Exercise performed on unstable surfaces does not transfer well to stable surfaces (our everyday life) nor do the risks outweigh any beneficial adaptation. In addition, some experts believe there may be a reduction in stable surface performance for the same exercise. When developing training programs for clients, fitness practitioners must incorporate the principles of exercise science into a program that will allow their clients to reach their goals. Unless your goal is performing in the circus, or doing a great job balancing on top of a ball, don’t waste your time training on unstable surfaces!