The Real Science Behind Instability Training

As you scroll through Instagram you’ll come across a lot of “gym fail” videos, typically involving the fitness enthusiastic attempting to “one-up” the next guy by doing some sort of loaded barbell back squat on a large stability ball.

While core strength and endurance have their place in your workout, attempting crazy exercises on commercial instability products (e.g., Swiss balls, suspension trainers, BOSU® balls, etc.) is just begging for trouble!

The initial intent of these devices was to garner improvements in balance and stability for those newly coming back from injury. The idea behind these instability devices is that they offer different planes of movement (side-to-side, forward and backward, and even diagonally) during which smaller stabilizer muscles have to work harder in an attempt to control posture and stabilize the body. This increases the challenge of the exercise to the individual.

The usage of these products has expanded beyond the initial intent, with application into sports, functional movement training, and even in elderly populations for fall prevention. For the gym-goer, the decreased stability adds an additional challenge to the core and stabilizer muscles during traditional exercises. Plus, these devices allow them to break away from the monotony of machines and the same old routine.

Because of their increasing popularity, fitness companies have flooded the market with instability products. These companies make outrageous claims that the products will increase core muscle strength, endurance, and even weight loss, yet the research may tell a different story.

To sort through these claims, and to prevent the misguided use of the products, let’s dive into a few of the more common pieces of instability equipment and see what the science has to say.

Swiss Balls/Stability Balls

These are the large inflatable balls that we were told to replace our office chairs with to improve our sitting posture and strengthen the lower back and core musculature. Although those recommendations showed inconsistent results, their use in the gym has become abundant. It seems that personal trainers reach for the nearest Swiss ball any chance they get to increase “core strength/stability” by performing every resistance exercise imaginable on them. However, according to research, performing traditional exercises (i.e., crunches, dumbbell chest press, shoulder press, lateral raises, bicep curls, and tricep extensions) on a Swiss ball shows no increases in abdominal activity compared to sitting on a flat bench [1].

For the most part, Swiss Balls are used for abdominal exercises; however, you occasionally see someone substituting the flat bench with the Swiss ball during their bench press routine in order to increase the challenge to the core. While good in theory, research has shown that performing the bench press exercise on the Swiss ball results in no differences in strength, range of motion, or muscle activity within the primary muscles (i.e., pecs, shoulders, triceps) or core muscles (i.e., obliques) [2].

BOSU® Balls

BOSU® balls are the double-sided, inflatable instability devices that offer users either a flat or rounded base upon which to perform exercises.

Depending on the side used, the BOSU® ball can give individuals various levels of instability for various exercises. For example, with the dome-side down, the ball is capable of multi-directional movements; however, with the flat portion down, the BOSU® ball provides an immovable base and unstable top.

But what does the research say? One study found that when bodyweight sit-ups were performed with the BOSU ball placed under the lower back (flat side down), there was no change in rectus abdominis activity; however, oblique activity actually decreased by 22–24% [3]! Additionally, power output has been shown to be compromised when performing squats on a BOSU® ball [4]. This research tells us that using a BOSU® ball in your training program may not only be ineffective, it may even be counter-productive!

Suspension Trainers

If you are unfamiliar with suspension devices, they are the crazy contraptions that gyms-goers hang from in the far dark corners of the gym. Suspension devices stem from the Olympic Rings, but the devices employ easier-to-grip handles instead of rings.

While used in gymnastics over the last century, suspension training has only recently become a phenomenon in the fitness industry. Suspension trainers are versatile and capable of hundreds of different exercises while using your own bodyweight as resistance. They range in cost from $60 to around $200 and can easily be set up in your home, office, or taken with you on vacation. Quite a few studies have been done on these devices and have provided some encouraging results.

For instance, Snarr et al. [5,6] found that performing push-ups on a suspension device increased activation of the abdominals to a greater extent than standard push-ups. Even more surprising was that abdominal muscle activity during the suspension push-up was just as great when compared to a crunch! When the suspension devices were used for strictly abdominal exercises (i.e., planks, pikes), the abdominal muscular activity was greater than that of standard abdominal exercises [7,8].

While most research has shown favorable results, research involving pulling movements, such as pull-ups or the inverted row, have shown no increases in muscle activity when using suspension devices [9,10].

Wobble Boards/Balance Boards

Wobble boards/Balance boards are most often used in rehab settings but often can be seen in personal training studios. Made of hardwood or plastic with a rounded bottom, these platforms offer an unstable surface in which most exercises involving standing on them.

While most research utilizing wobble boards exists in the physical therapy realm, a few studies have been performed using traditional resistance training movements. For example, the aim of one study was to see how muscle activity changed when highly-conditioned individuals performed two tasks on the wobble boards: standing and bodyweight squats. When the individuals simply stood on the boards, most of the muscles in the legs and some core musculature actually increased in activation [11]. However, when the subjects began performing squats, the only muscles that showed increased activity were the lower abs and calf muscles.

Multiple Devices

Although results of multiple studies have shown that using an instability device may increase core muscle activity, adding more devices does not equate to even more muscle activity output. For instance, Byrne et al. [1] showed that while planks performed with the arms in a suspension device increased activity of the abdominals and obliques, there was no difference when a suspension device was added to the feet.

Now that we have examined some of the research out there, we can see that the results are very inconclusive. It sounds like a late-night infomercial, but “Individual results may vary” rings completely true when dealing with instability training. Individuals experience and correct their posture differently when placed upon unstable surfaces so those with poor core strength and balance may see greater results than others.

While instability has its place in your workout, it doesn’t need to be used with all of your compound lifts. If you are looking for a challenge or even a little bit of fun, then by all means, grab the nearest instability device; just don’t expect substantial gains in strength or power.

References:
[1] Lehman GJ, Gordon T, Langley J, et al. Replacing a Swiss ball for an exercise bench causes variable changes in trunk muscle activity during upper limb strength exercises. Dyn Med. 2005;4:6.
[2] Goodman, CA, Pearce, AJ, Nicholes, CJ, et al. No difference in 1RM strength and muscle activation during the barbell chest press on a stable and unstable surface. J Strength Cond Res. 2008; 22(1):88–94.
[3] Saeterbakken AH, Andersen V, Jansson J, et al. Effects of BOSU ball (s) during sit-ups with body weight and added resistance on core muscle activation. J Strength Cond Res. 2014;28(12):3515–3522.
[4] Zemková E, Jelen M, Kováciková Z, et al. Power outputs in the concentric phase of resistance exercises performed in the interval mode on stable and unstable surfaces. J Strength Cond Res. 2012;26(12):3230–3236.
[5] Snarr RL, Esco MR, Witte EV, et al. Electromyographic activity of rectus abdominis during a suspension push-up compared to traditional exercises. J Exerc Physiol online. 2013;16(3):1–8.
[6] Snarr RL, Esco MR. Electromyographic comparison of traditional and suspension push-ups. J Hum Kinetics. 2013;39:75–83.
[7] Snarr RL, Esco MR. Electromyographical comparison of plank variations performed with and without instability devices. J Strength Cond Res. 2014;28(11):3298–3305.
[8] Snarr RL, Hallmark AV, Nickerson BS, et al. Electromyographical analysis of pike variations with and without instability devices. J Strength Cond Res. 2016;30(12):3436–3442.
[9] Snarr RL, Esco MR. Comparison of electromyographic activity when performing an inverted row with and without a suspension device. J Exerc Physiol online. 2013.16(6):51–58.
[10] Snarr RL, Hallmark AV, Casey JC, et al. Electromyographical comparison of a traditional, suspension device, and towel pull-up. J Hum Kinetics. 2017;58:5–13.
[11] Wahl MJ & Behm DG. Not all instability training devices enhance muscle activation in highly resistance-trained individuals. J Strength Cond Res. 2008;22(4):1360–1370.
[12] Byrne JM, Bishop NS Caines AM, et al.. Effect of using a suspension training system on muscle activation during the performance of a front plank exercise. J Strength Cond Res. 2014; 28(11):3049–3055.