What are disadvantages of using unstable surfaces? The inherent disadvantage of using unstable surfaces is that the ground moves under you. This only happens in a few sports. If the surface is too far away from the normal competition surface there is a risk of developing a skill set that makes them able to handle the very unstable surface but has no relationship to the actual activity. The danger is that overuse of the unstable surface will create artificial stability. Artificial stability is a stability that is adapted to the specific task required by the unstable surface, but is of questionable value in regards to transfer to actual performance. The stability gains need to transfer or it is time wasted. Beware of turning the use of unstable surfaces into circus tricks. A good example is standing on a physioball, except for a very few sports that is no carryover, it is a discrete skill that stands alone. There is no need to learn that to improve sports performance. That time would be better spent doing more sport appropriate activities.
A sound approach is to create instability through movement. Is the normal environment enough? Can we simply employ a few environmental modifiers? An environmental modifier is anything that creats an increased propriocpetive demand that elicts a response that is similar to that requires by the movements of the sport. So the questions you must ask are: What will transfer? What will not transfer? What will create a skill set that will not transfer?
There are three clear objectives for using unstable surfaces:
Injury Prevention – Scandinavian and Italian studies prove their value for prevention using unstable surfaces as part of warm-up.
Performance Enhancement– There is not much hard data in this area, the results are basically anecdotal.
Rehabilitation from an injury– This proceeds from very controlled closed skills to open reactive movements that indicate an ability to react and utilize the surface.
There is certainly significant overlap between the three; in essence it is a continuum.
How much should you use unstable surfaces once the sport demand has been assessed? It is best used as remedial work preceding warm-up in an injury prevention mode. For performance enhancement it should probably be placed within the body of the actual workout. It is probably most compatible with agility work or lower body strength training. Success or failure in most over ground sports is determined by how effectively the athletes are able to use the surface they compete and train on. The surface will give back energy or dampen force.
Where possible a good step is to take the shoe out of the equation. Perhaps the simplest way to manipulate the surface is the do some activities barefoot. Because of the abundance of proprioceptors in the bottom of the foot this affords the possibility for heightened sensory input. Explore the simple and obvious before going to the complex. Work barefoot will have a quick and obvious transfer.
The following are unstable surfaces that I have found effective:
Sand – Sand is a viable unstable surface to in both training and rehab. Just like any surface it has some limitations. The primary downside is that the softness of the sand significantly slows everything down. It dampens the elastic response, which is both a plus and a minus. It is a plus because it develops good concentric strength response. It is a minus because it negates elastic response, so it is not real life. That being said sand enables big angles and aggressive movements that allow the athlete to push the edge in terms of lateral movement.
High Jump and Pole Vault Pit – The depth of the pits dampens impact so it is a decision of how much do you want of this. This virtually eliminates any elastic response. The work on the pit is dominated by concentric muscle action. This is a good surface that can be used for canoe or kayak to simulate the training or competitive environment on dry land.
Trampoline – Very responsive, obviously bouncy which is good for body awareness and control. A trampoline is a good surface to work on landing and sticking the position to create stability.
Gymnastics Floor Exercise Floor – There is a very predictable response from the floor. A very springy surface. Good surface to work on barefoot.
Resilite Wrestling Mat – This surface is not as responsive as a floor exercise floor. Good for multidirectional activities because of the size of the mat. Another good surface for barefoot work.
Foam Pads – Smaller high-density foam pads are good for static balance activities. This represents a very controllable instability.
K boards – Good to great side-to-side instability. The pivot point of the board only allows movement in the frontal plane.
Wobble Boards – The pivot allows three hundred and sixty degrees of motion, so this creates a rotational instability.
BOSU – (This is not meant as an endorsement of the BOSU.) Using the flat side allow three hundred and sixty degrees of motion as well as a tipping effect. The degree of instability is determined by the inflation level of the BOSU.
Leather Medicine Balls – These are great to step on and off or one onto another in a stepping stones patterns. They are very effective when combined with a several BOSU’s. Excellent tool for ankle and knee stability.
Balance Beams – The edges of the beam should be beveled to create a bit of instability. This allows movements forward back and side to side. Also good apparatus to use for single leg squats.
Remember not all surfaces or apparatus are appropriate for all situations. A good craftsman knows how to effectively use the tools in the toolbox; a hammer cannot replace a screwdriver. These surfaces and apparatus are analogous to the skilled craftsman’s tools for the coach and therapist. Use them sensibly, more is certainly not better, be very specific. It is beneficial to introduce a play element- this will allow the athlete to playfully explore the dimensions of movement required by different surfaces.