Unstable surface training has become a popular concept in fitness training. Vibration platforms and bosu boards are becoming mainstays in commercial gyms as they try to entice their customers with varied forms of training based entertainment. Is it all a waste of your time though?
Initially, it is important to look at the background of where these methods of training have emerged. Unstable surface training has progressed in to the “training” environment due to the greater role that physiotherapy and rehabilitation has played in the industry over the last 10 years. To understand further it is important to look at training fundamentals as well as how these methods apply to injured and non-injured trainees.
The body as a whole is a series of joints working through the ankle, knee, hip, back and shoulder. Each of these needs an adequate supply of mobility and stability/ strength. If we have comprimised stability at one of these areas it can cause injury- not necessarily though where there is a lack of stability but at a different point in the body. For example, poor hip stability is associated with knee pain. If mobility is lacking in a certain joint again pain may be felt in another area of the body, for example a forward rounded shoulder posture indicates poor mobility in the upper back (thoracic region) and can cause issue with mobility at the shoulder joint.
The concept of unstable surface training indicates that more muscle mass will be recruited if unbalanced. Is this the case though? Two things recruit muscle mass, speed of movement and load. Unstable surface training comprimises both of these as you cannot either move as quickly as possible or indeed safetly load maximally. Muscular recruitment is task dependant and therefore only relevant to the movement being performed.
Unstable surface training for the lower body is more relevant to a rehabilitation based environment. Indeed it has no real carryover for those looking to enhance performance if uninjured (Cressey, E.M. et al. J Strength Cond Res. 2007 May;21(2):561-7). When we provide an unbalanced environment for example a lunge or step up on a vibration plate or a single leg squat on a bosu a number of things will happen. Firstly, the body will aim to maintain stability, the mechanism for this is that the body will start to tighten up. Is this a good thing? It is interesting that most vibration trainers start pointing at the torso area when discussing the benefits of this type of training when really the ankle will tighten up first and shut down mobility to maintain balance. As discussed before if mobility is shut down at a joint then it can casue undesirable movements from joints further up the body to maintain balance. Usually this will be at the knee which is an area of massive stability (it is a hinge joint after all so does not like excessive rotation- which unstable surface training can encourage). If you consider how force is applied to the human body from a day to day perspective, very rarely does the ground move beneath us. Indeed we have to be able to move across varied terrain (for example, cross country running). This though is not through a full range of motion at the ankle, hip or knee. Indeed the forces are reactionary in nature, short lived and through a limited range. Most forces will act on the human body above the floor either by collision or by changes in loading or centre of gravity- consider falling over and trying to stop it happening- you tighten up from the top down rather than the bottom up.
When is this training relevant though? Well looking to improve proprioception in the lower body is vital- escpecially on return from an ankle injury. Building eccentric strength and the ability to absorb force are fundamental qualities of a rehab programme intially before returning to more advanced forms of training. After this the focus moves towards the transferance of force and power generation ultimately in a multidirectional format. Methods of unstable balance training could be argued as a valid as entry point for rehabilitation. Once the ability to control load has been assessed to be suffcient to perform more advanced training under increased training loads then unstable surfaces lose their priority in the hierarchy of needs. The evidence for these methodologies though is stil not resounding even in rehab situation indeed some studies have even shown an increase in injury risk post unstable surface training intervention (Soderman, K. et al., Knee Surg Sports Traumatol Arthrosc. 8(6):356-63. 2000).
For the upper body there is an improved arguement. Due to the nature of the shoulder joints need for stability and the relevance of how forces act on our extremeties being able to react to unstable loading can be beneficial. This is not saying that one legged/ one arm vibration plate shoulder press is the way to go. More that unstable loading for the shoulder joint can be a challenge which encourages force production and torso stability without comprimising the role of the shoulder joint and it’s range of motion. This would not be a priority exercise in a programme but performing press ups (weighted vest for load) with the hands on the unstable surface may be relevant for scapular and torso control as an assistance exercise or indeed dynamic core drill.
How does this apply to the average exerciser or indeed even the elite athlete? It’s pretty much the same. Most people need enhanced strength- this is not gained by balancing as it comprimises load and speed of movement. Strength and it’s varied componenets such as power and endurance are the fundamental capability we are looking to develop as well as the ability to move and perform exercise in a posturally correct way. Enhancing the quality of movement is key and this is done by balancing mobility and strength in tandem usually against resistance which includes your body weight.
So why the prevalance of unstable surface training in the fitness industry? These concepts are relevant for some people, the injured and the completely detrained. If someone is new to training then unstable surface training may help them improve- but doing anything will help them improve from a strength perspective, escpecially if it is delivered in a structured format. If they increase participation then from a “health” perspective it is probably better then doing nothing. This form of training provides “entertainment” away from other more traditional exercises- however as you can see it is a regression in training rather than a progression as although changes in exercise complexity may make you feel like you are working harder in truth you may be comprimising your progress.