To use stable or unstable exercises, that’s the question

Unstable surface training (UST), also referred to as stability training (ST), has gained tremendous popularity in the last several years. Unfortunately, for the average person just trying to improve themselves physically, the popularity of stability training has exploded into the mainstream. Why do I think this explosion in popularity is unfortunate? Because, like any industry, the fitness industry is full of people trying to make a buck anyway they can.


The fitness industry preys upon people’s insecurities; the fitness industry is always looking for something new because of the ease at which they can hook consumers with an “easier”, “faster” way to look better. UST is not popular because it is more efficacious than traditional training, but because of a tremendous media campaign. They know there’s huge money in marketing a piece of equipment and/or workout program, especially when it’s backed by pseudo-scientific studies.

Some UST device advertiser’s claim their product is the key to achieving a strong, fit, balanced, functional body. They claim that no longer does one need to lift weights, push them self to get stronger, or even go to a gym. Just use an advertised device, like the Bosu ball, with a few dumbbells or just body weight, and viola! You will magically become fit. They are preying on people’s ignorance, and in many cases, inherent laziness.

Truth be told, UST has only proven its usefulness in the rehab setting and only with respect to ankle stability to any degree. There is no research to support the efficacy of UST in healthy people over traditional training. Several studies report that training on an unstable surface offers no increase in the electromyography (EMG) of the muscles involved in core training and no increase in athletic performance.

UST exercises have been shown to adversely affect movement velocity and range of motion when performing traditional ground based exercises like the squat. Hence the ability to exert force, power or move at high velocity is hampered during UST. This is simply because the loads needed to perform the exercises are too light to produce a significant adaptive response. These results are not conducive to building strength, muscle or explosiveness.

The truth and nothing but

UST has moved from being used almost exclusively in rehabilitation to becoming common place among persons who call themselves personal trainers and strength coaches. One can’t go to a gym and not see somebody training on a Bosu ball, stability ball, wobble board or foam pad. It’s so popular, entire books have been written on this type of training using these circus props. But do not be fooled by its popularity.

Be very wary when you see or hear a study referenced in a commercial, article or book. Chances are they are extrapolating information, and drawing false conclusions in order to add credence to their product. Take a little time, find the study that an ad is referring to, and read it.

Before the internet

Consumers need to scrutinize everything from doctors to lawn care personnel. If you’re going to spend your hard earned money, make sure it’s worth it; this includes purchasing fitness products of any kind.

Before the internet, it was easy for manufacturers of fitness products to use studies to back their claims with very little examination by consumers. This is because, in order to research the claims of a product, one had to invest a good amount of time and effort going to the nearest library. The average person just didn’t have the time to do this. With the advent of the internet, this has all changed.

What used to take hours now takes the average person seconds by using Google, Bing, Yahoo and other search engines. A wealth of information is at your fingertips. However, just because you find the information doesn’t mean it will be of any value. Studies can be very hard to understand if you have no knowledge of the vocabulary used or how to read them.

It’s not my intention through this article to teach Research 101. However, I would like to offer a few tips so you can start to educate yourself about the claims others make. Who knows, you may even find reading some of the references from an article or advertisement to be interesting.

Since this is an article about UST, let’s start off by reviewing a few studies concerning this topic. You’ll see how studies can be used to add credence to a product or article, even though in reality they fall short. The extrapolation of information from studies to be used to sell a product is not only unethical, it’s all too common.

One study I have seen referenced in articles in order to substantiate the use of UST in traditional strength training routines was performed by researchers from Occidental College in Los Angeles, California. They compared the EMG activity between a stability ball crunch and a traditional crunch. Forty-one healthy subjects with an average age of 20 participated. Two variations of the stability ball crunch were performed. One with the ball located between the bottom of the scapulas and one with the ball at the level of the lower lumbar region. All subjects were instructed on how to perform the exercises correctly. The results showed the stability ball crunch, with the ball in the lower lumbar region, had higher EMG activity than that of the traditional crunch. On the surface, this study seems to back the validity of unstable training.

According to the authors, “it was not the purpose of this study to determine how best to perform a crunch motion to maximize its effectiveness but rather, given similar speed and range of motion across crunch movements, to determine how modifying ball position with respect to the spine effects muscle activity while performing a crunch motion.”

As with many fitness and strength training studies, there are many holes in this one for the media to use the results outside of what the study was intended to show. First, the study doesn’t mention whether the subjects were trained or untrained, so I’m going to assume they are untrained. This is unfortunately all too common. An untrained individual simply has not developed the ability to generate force to the extent of somebody who is trained. Hence, these results are only transferable, if at all, to the untrained or injured; the results should not be used to justify UST in traditional strength training programs.

Second, and most importantly, the load used for claims outside of what the study was intended for was too low. Each exercise was performed for 8 – 10 repetitions using no resistance. The only variable in difficulty was the unstable surface, and it has never been proven that unstable surface training, with increasing loads or not, increases strength. In order for a study to have any value in establishing differences in efficacy between exercises, the sets need to be performed to failure using trained subjects.

A second study that I’ve seen many authors and educators take the liberty of misapplying the findings of was performed by researchers from Canada. Eight subjects performed four different curl-up (crunch) exercises; one was performed on a stable surface and the other three on unstable surfaces. The EMG activity was recorded for all exercises.

As with many studies comparing muscle activity of exercises on stable and unstable surfaces, the exercises performed on unstable surfaces outperformed the muscle activity of the stable surface crunch. Although the authors conclude the interpretation of the data in their study is limited because the subjects were relatively physically fit, and the tasks were designed to be non-fatiguing, this study is used by others to establish the efficacy of UST for enhancing sports performance.

As with the first study, the two major holes in applying this study to tradition strength training programs are the loads used and the use of untrained individuals. Another concern I have is the number of participants. The more participants a study has, the more power it has to detect effects. Eight participants is dismally low, even for the study’s purpose.

Getting to the core of stability

The core is the area between the hips and the lower chest; it can be considered the connection between the upper and lower extremities. A stable core provides a pathway for the extremities to transfer force between them. For instance, a baseball pitcher generates force in his legs and hips, which transfers through his core to his throwing arm. It’s like a complex catapult. If the pitcher has a weak core, the force generated by his lower body will be somewhat lost before reaching his pitching arm.

Many strength coaches, trainers, etc. surmise that UST allows one to improve their performance under more stable conditions like exercises and sports. This is not backed up at all by science or empirical data. A program centered on “functional,” unstable surfaces is just silly.

The main function of the core is spinal stability. The spine is at its strongest and least susceptible to injury in a neutral position, especially during movement, e.g., sports and weight training. However, the question is what type of training is most efficient at training the core to provide stability to the spine? And the answer is programs that center around basic, traditional lifts with 100% intensity, e.g., barbell squat, deadlifts and various types of presses. This type of training is the correct stimulus to elicit an adaptive response to the core. Performing squats on a Bosu ball isn’t going to do jack shit compared to balls to the wall barbell squats in the way of functionality or sports performance.

Bottom line: if you’re creating a weight training program, use unstable surface training sparingly. If you’re looking to gain increased performance, (e.g., speed, strength, explosiveness) don’t try don’t expect much using circus props like wobble boards or Bosu ball balls. Too many coaches and trainers are doing a disservice to their athletes by de-emphasizing traditional weight training and going overboard with functional BS.