The Pros and Cons of Training on Unstable Surfaces

 

Training on unstable surfaces owes most of its development to rehabilitation, where it originated.  There are many unstable training surfaces including physioballs, foam pads, inflated rubber disks, and Bosu’s.  These surfaces are used on the training floors of most gyms. 

The idea behind unstable training is that inconsistent motion stimulates sensory apparatus in the muscles and joints leading to increased sensory input and increased muscle activation.  In addition, these movements cause muscles on both sides of the joint to co-contract.  Co-contraction occurs to some extent during virtually all movement.   When we significantly increase co-contraction, the result is increased joint stability.

Increased co-contractions from unstable training can be very useful in the treatment of ankle instability and lumbar spine injury.  However, when we use a concept originally developed for rehabilitation, we need to carefully evaluate how and when to use this approach in healthy or athletic populations.

For example, many trainers have clients perform shoulder presses while sitting on a physioball or standing on Bosu to increase core muscle activation.  However, this does not produce the desired result.  Studies show that doing shoulder presses on an unstable surface does NOT increase core muscle activation versus the same exercise done on a stable bench.

The reason for this result is that balanced vertical forces in alignment with the spine do not increase core muscle activity – regardless of instability of the surface the exercise is performed on!  The use of asymmetrical loading, such as doing a one-sided shoulder press, does increase core activation.  However, this core activation is not increased further by being on an unstable surface.

Horizontal limb movements also increase core activation, but there is not a lot of evidence that adding an unstable surface increases this benefit.

When it comes to lumbar (low back) stabilization, research shows that exercises done on unstable surfaces like Bosu Balls in a horizontal position (face up or face down) does increase core muscle activity.  Exercises like crunches, bridges, and push-ups on an unstable surface will result in increased core activation. 

Unstable Surfaces are NOT good for Strength and Power Development

When it comes to absolute force production performing exercises such as bench press or squats on an unstable surface, force production significantly decreases and does not assist in the development of absolute strength.  So when training for increased strength, performing exercises on stable surfaces is a better choice.  

This same thing is true when working on increasing sprinting speed because training on a highly unstable surface increases ground contact time and decreases force production, inhibiting acceleration.  However, doing specific drills on a firm surface that provides slight rebound as PART of a sprint program can produce benefits. 

The other consideration when using unstable surfaces like a Bosu is that lifting mechanics are significantly altered.  Researchers have suggested that training on highly unstable surfaces can actually increase the risk of knee injuries in certain populations!  Not to mention the risk of injuries also increases from hopping, jumping, and leaping on and off of unstable surfaces!

How to Properly Use Unstable Training 

For healthy and athletic populations research suggests that a combination of unstable and stable training will provide the best results.  This brings up two questions:

            Which should come first: stable or unstable?

            What level of instability should be used with each particular person?

The answer to the first question is dictated by the rules of proper progression.  The three primary phases of stabilization training include: 

·       “Static” Stabilization (foundational)

·        “Dynamic” Stabilization (strength/endurance)

·        “Ultra-Dynamic” Stabilization (power)

 Within each phase:

·       Start with bilateral strength development (meaning both legs and/or both arms) in stable environments because it is safer and will increase strength more.  

·       Next progress to stable single limb challenges in a stable environment

·       Then progress towards hopping and jumping skills in a stable environment

·       Then apply that new strength and power to tasks involving postural control on unstable surfaces.  

When it comes to how much instability to use with each person, the answer will depend on the goal of the exercise and the ability of the individual.  Ideally you will use different levels of instability according to the goal of the exercise and the ability of the individual!