// Training on unstable surfaces - the missing link

by Douglas Brooks

I heavily favour training on labile (movable or unstable) surfaces such as BOSU® Balance Trainers, stability balls, foam rollers and balance boards. But I also believe that training on unstable surfaces is only one part of a results-oriented and complete training approach.

Subscribing to either the functional training enthusiast’s point of view (pro-unstable surface training) OR the traditionalist’s view (less convinced of it’s benefits) doesn’t allow for a balanced view of training. As an industry, we should seek to represent a full understanding of what both types of training can and cannot accomplish.

If a single approach is chosen to the exclusion of another, and both are framed within a scientific parameter and deemed ‘useful’ at the least, training ‘one way’ would represent an incomplete training approach that doesn’t cover all facets of need. As researchers and fitness professionals we must acknowledge that a traditional approach to improved performance is simply different when compared to training on unstable surfaces. Both genres of training have something substantial to contribute to training outcome, whether it pertains to high level sport performance, back rehabilitation, or real-life movement challenges and responses.

Functional training controversy: science versus science?

It seems that two sides have evolved with regards to whether or not functional training can have an impact on performance. It is important to remember that everyone has performance goals, ranging from world class athletes to frail, older adults. Experts on both sides are in agreement that proprioceptive training is valuable for rehabilitation. Ongoing research into unstable training surfaces, and integrated training approaches, points to additional training benefits in favour of these methods (Gamble 2007; Chieu, ed. 2007; Behm and Anderson 2006; Brown, ed. 2002, 2005; Myer et al., 2005; Anderson and Behm 2004; Willardson 2004).

How can two sides which both base their claim on science be at such odds? One of the difficulties as it relates to objective test data is for researchers to determine how to measure balance and performance improvements in people who have normal balance capability. Additionally, many of the issues will come down to semantics and how we define training results as they relate to performance.

This topic will be greatly affected (and limited) by current testing methods and interest in this type of training. Fitness professionals and consumers are trying to sort through the seemingly contradictory information and it is placing a burden on the scientific community to provide answers and guidelines with regard to what this type of training can and cannot accomplish. Fortunately, this scenario will accelerate discussion, research and learning.

Ultimately, for an understanding of the subject to move forward, both sides will have to move from all-or-none positions and acknowledge the value of traditional approaches to training, as well as identify exactly how functional and integrated movement approaches contribute to improved performance. This would encourage future research that will be able to more precisely define the outcome when one trains on unstable surfaces and its impact on performance improvement (Gamble 2007; Behm and Anderson 2006; Brown, ed. 2002, 2005; Myer et al., 2005; Anderson and Behm 2004; Willardson 2004; IDEA 2003).

In fact, Myer (2005) and his colleagues concluded that the results of their study ‘support the hypothesis that the combination of multiple-injury prevention-training components into a comprehensive program improves measures of performance and movement biomechanics’. The study used some unstable training surfaces, including the BOSU® Balance Trainer. Behm and Anderson (2006) conclude ‘both stable and unstable exercises should be included to ensure an emphasis on both higher force (stable) and balance (unstable) stressors to the neuromuscular system’. The take home message is that we must stop drawing only on past research to support a bias or status quo, which of course, would only support traditional approaches for performance improvement.

It is obvious that functional or proprioceptive training programs work. Functional balance and integrated (linked) training teaching methodology, whether performed on stable or unstable surfaces, should be built on an understanding of the ‘why, when and how’ behind exercise choice, implementation and progression. Rather than taking a haphazard approach to designing functional training programs, or not fully understanding why this type of training is being offered, it is therefore important to identify what is being accomplished with functional training workouts. It is also important to understand why and how personal trainer network functional training dovetails with, and complements, other science-based aspects of a general fitness and performance training hierarchy. Obviously, more research is
needed in this emerging field.

Strategies for balance training focus on increasing sensory input in a variety of training environments with different proprioceptive challenges that include; stable or unstable surface, visual affect, contact points, movement ROM, speed of movement and external stimulus (Blahnik, Brooks and Brooks 2006; Blackburn et al. 2000).

Ultimately, central nervous system training will improve motor skills, kinesthetic awareness, balance and ultimately, muscle responses that maintain stability. Maximal force/strength/power output is generally nOT the goal, whereas integrated, linked movement capability and force output reflective of real life requirements and many sports, is the focus. Integrated or linked training, independent of the type of surface
you train on, bridges the gap with traditional strength training. The training focus shifts from 1) training primary to secondary fitness characteristics; 2) isolation-based training to movement-based training; 3) unidirectional to multidirectional movements; 4) defined / restricted ROM to variable ROM; 5) muscle-based to neural-based timing and reactivity training (Clark and Twist, 2005).

Training progression is a moving target based largely on the principles of cross training and periodisation, as well as related goals and an individual’s current fitness level. Though there is not a wealth of information to scientifically support a black and white approach to training on unstable surfaces, nor is their enough research to support unequivocally that the approach is futile and off target. There is an obvious place for traditional and integrated balance approaches in the health/fitness, rehabilitation and sport performance worlds. Setting up a pre-biased war of words and opinion (‘for’ vs. ‘against’) is counter productive and leads us from a common ground of understanding with regard to when, or when not, to use this, or any type of specific training for that matter.

Finally, it is important, not so much to cite numerous studies on proprioceptive training, rehabilitation and sport performance improvement, but to attempt to foster a community of professionals who are open to and willing to define what training on unstable surfaces brings to the conditioning, rehabilitation and sport performance arenas.

A new mind-set and outlook must be fostered to further and objectively look at ‘balance training’ research on unstable surfaces. To think that training on a lifting platform using free weights and running agility drills on stable surfaces would cover all life and sport applications is ludicrous. Equally absurd, would be to state that functional/balance / proprioceptive training on unstable surfaces would entirely replace these traditional approaches and would stand alone in its ability to accomplish all training needs.

like it or not, based on both plentiful research and anecdotal evidence, unstable surface training is here to stay. The results are trickling in quickly, and to say the least, they’re promising and support training on unstable surfaces as part of a multi-disciplinary approach that can completely and effectively prepare a body for any number of ‘performance’ training goals. In your search for truth as you evaluate various training methodologies, ask yourself, ‘Can the training process be enhanced? If so, ‘game on!’

Balance training research

An entire body of scientific literature stands behind balance and stability training, postural stability and the body’s ability to maintain centre of mass or gravity. The benefits of training controlled instability on unstable surfaces are many, and as it relates to postural stability, has become increasingly recognised in the realm of sport and rehabilitation (Anderson, Gregory 2005; Blahnik, Brooks and Brooks 2006). An irony of past balance research is that researchers have found it difficult to measure or show balance improvements in individuals who have ‘normal’ balance. However, that does not mean that improvements do not occur. limited research has been performed on unstable surfaces with healthy or highly conditioned athletes. Data (Behm et al. 2003, 2005) suggests that trunk stabiliser muscles are activated to a greater degree by unstable versus stable exercises and that unilateral resistance exercises cause greater muscle activity in the contra-lateral (opposite) side trunk stabilisers. Exercises that include an overhead shoulder press while seated on a stability ball and squat exercises performed on progressively more unstable surfaces, have demonstrated this increased muscle activation (Anderson and Behm 2005). Both McGill (2001, 2002, 2004) and Vera-Garcia (2000) showed increased muscle activity on an unstable surface when compared to a stable surface. It is important to remember that the goal of training on unstable surfaces is to increase muscle activity without necessarily increasing load. Recent studies have focused on integrated approaches to core training using stable and unstable surfaces and whether or not they are necessary (Gamble 2007; Chiu, ed. 2007).

Balance research and the older adult

Balance research has historically focused on older adult populations because this group is at an increased risk of fall related fractures. Because proprioceptive feedback capability is often reduced in active or diseased older adult populations, this group can show marked improvement in both balance and physical improvement even with non-specific, or non-balance focused conditioning approaches.

Research also shows that specific strength and/or balance exercises enhance stability and reduce the risk of falling, as well as increase overall physical performance (laStayo et al. 2003; Spirduso 1995; Judge et al. 1993).

Balance research in rehabilitation and injury prevention programs

Significant research has focused on injured and disabled populations. Restoring (rehabilitating) or maintaining (preventing) proprioception allows the body to maintain stability and body orientation during static and dynamic activities. During rehabilitation, proprioceptive programs are specifically tailored to each patient, and as is true for any functional rehabilitation program, should include balance training, closed-kinetic chain exercise (CCE) like leg presses, single leg balance, hops or jumps, back strengthening exercise and quadruped stabilisation (i.e., position on the hands and knees or ‘all-fours’ to stabilise the scapulae in a closed-kinetic chain position), as well as sport specific training and drills (Carmeli et al. 2003; McCurday and Conner 2003; Gauchard et al. 1993; Judge et al. 1993; laskowski et al. 1997).

It is believed that impaired ‘joint position sense’, when overlooked in a rehabilitation program, may be a leading cause for recurrent injuries. On the other hand, proprioceptive and balance training have been shown to significantly reduce the incidence of anterior cruciate ligament (ACl) injury in soccer players (laskowski et al., 1997, pg. 97). The goal of proprioceptive training during rehabilitation is to maximise protection from injury and restore one hundred per cent, or optimal, function (laskowski, et al., 1997). From this perspective, it would make perfect sense that this type of functional and balance training would be a necessary part of any training or rehabilitation program, and be appropriate for all types of people, regardless of program goals.

Rehabilitation and injury prevention oriented programs can be designed to challenge, enhance and improve the proprioceptive system. By affecting (training) various central nervous system pathways and reflex arcs, ‘prophylactic’ (protective) proprioception training programs may protect against injury (Caraffa et al., reported in laskowski et al., 1997).

Static and dynamic joint stability

A major category of proprioceptive or functional training is balance training. An example of training the proprioceptive system and joint stability in a mostly static way includes one-legged standing balance exercises. The ability of appropriately activated muscles to stabilise a joint during more complex movement defines dynamic joint stability (laskowski, 1997, pg. 98). Progressive and dynamic challenges, for example, hopping from one Balance Trainer dome to another on one leg, jumping vertically and landing on the dome or performing pushups on the platform side of the Balance Trainer while simultaneously keeping the platform level, changes the nature of the required joint stability to ‘dynamic’.

Douglas Brooks, MS
US fitness professional Douglas is the consulting exercise physiologist of product research and development for a number of fitness companies. He is the author of six books and shares his conditioning expertise with baseball players, motocross racers and downhill skiers, to name but a few. In 2007 Douglas was inducted into the USA National Fitness Hall of Fame.