A friend of mine asked me to look over his training routine a while ago so I met up with him at his gym and walked through the drills he was doing. His main goal was what I call "image building". He wanted to look good. Muscled. Ripped. Toned.
One of the drills that was suggested by a trainer was a dumbbell chest press while lying on a swiss ball. He knocked out about 15 reps using 35 lb dumbbells. I asked him why he used the swiss ball and he said his trainer told him that it would make him work harder and make the exercise more effective.
Does it? Do drills like a chest press or an overhead press become more effective if performed on a Swiss ball?
Swiss balls made their way into rehab a long time ago. They create perturbation by being an unstable surface. The idea was to challenge balance, proprioception, and spinal muscle endurance. And they work well for those things.
Stuart McGill, a spine researcher form Canada, has measured the work loads of the spine during various exercises. His research shows that just sitting on a swiss ball increases the muscle activation of the lower back substantially. He argues that the use of a swiss ball as an office chair should be used carefully in people who have chronic low back pain because their stabilizer muscles will fatigue rapidly.
Along the way, therapists and trainers let their creative side run wild with the use of the swiss ball and began doing all sorts of exercise on it. I've even seen people perform squats standing on a swiss ball.
But, Wall and Behm demonstrated in their research using swiss balls as an unstable surface while performing various exercises that the unstable surface reduces the muscle activation of prime movers. In other words, your body spends more energy and recruits other muscles trying to stay on the ball and reduces the amount of muscle activation used in the main movement.
To improve muscle size and tone you have to overload the muscle. That means a progressive increase in training loads and speeds. A swiss ball will limit how much you can increase the load and speed simply due to the unstable nature of it. And, at some point, the instability raises the risk of injury as you try to overload the muscle with increasing levels of resistance.
Bottom line - if your goal is to increase strength, improve muscle tone, and look better, swiss balls are not the best choice.
Swiss balls and iron don't mix well.
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Wahl, M. J. and D. G. Behm (2008). "Not all instability training devices enhance muscle activation in highly resistance-trained individuals." J Strength Cond Res 22(4): 1360-70.
