Swiss balls and unstable surfaces – variety, fashion or functional training?

Different kinds of balls (bosu, ovoball, Swiss) can be found in clubs and gyms. Because of low price – many people also have such equipment at home. Is it only fashion, or are such accessories essential for efficient workout of temporary sportsmen?

There is no clear-cut answer to this question. If you want to increase strength and muscle mass – majority of your workout should be done on a stable surface. Why? Because each kind of unstable surface (e.g. Swiss ball) makes you weaker. Among other effects, the loss of 8% of strength was observed during barbell press on a ball comparing to barbell press on a bench. That's not all – the work of goal muscles during this exercise on a ball was smaller (the biggest loss was in the area of chest – 19% and triceps – 31%), but also in e.g. Bulgarian squats the collateral muscles (hamstrings and obliques) worked much harder. Conclusion? Exercises done on a ball should be only complementary to the basic strength workout. In the aspect of safety, e.g. the options of barbell press and squats with load, are very dangerous when performed on unstable surface. It's easy to hurt yourself or get injured.

What does scientific research say about the work of muscles during exercising on a ball?

In one of the latest studies published in June 2015 [1], it was checked how unstable surfaces (e.g. hanging on TRX tapes) and balls activate muscles in the body. Eighteen elite swimmers at the age of 15.5 ± 2.3, with height of 163.3 ± 12.7 cm and weight 62.2 ± 11.9 kg took part in the experiment. The work of their muscles was measured with electromyography – the engagement of rectus abdominis, exterior obliques, erector spinae. The strength of any maximal contraction for particular muscle groups was measured (reference point). The work during statistic tension of abs and back was measured with Swiss ball (the position of plank) and withouth the ball. In the second attempt similar position was achieved thanks to the system of hanging tapes (similar to TRX). The suspension of the body caused harder work of rectus abdominis comparing to the attempt with Swiss ball or the plank exercise without the ball. But the result was not the same for obliques and spinal erectors.

Unfortunately, another study proves that for moderately active people even advanced exercises with the ball are not so efficient. The only exercise which caused the same effect as strength training was the bridge. However, as the scientists add, the difficulty and risk of more advanced workout on the balls is disproportional to the effects [2].

The next study [3] mentions the efficiency of the following exercises:

  • roll-out

  • pike

  • knee lift sitting on a ball

  • skier

  • extending hips to the right and left

  • push-ups with legs on the ball

  • “marching sitting”

Additionally, the efficiency of crunches and crunches to the knees was checked. The electrical activity of muscles during exercises was measured with sEMG and compared to the maximal contraction (isometric) of particular muscle group.

DESCRIPTION: One of the best exercises with a ball – roll-out:

The results of the experiment?

  • The best exercises are roll-out and pike (63% and 46% of maximal engagement of the upper part of rectus abdiminis),

  • lower part of rectus abdominis: 53% roll-out and 55% pike,

  • external obliques: 46% roll-out and 84% pike,

  • internal obliques: 46% roll-out and 56% pike.

The remaining exercises caused worse effects:

  • 7-53% for the upper part ofrectus abdominis

  • 7-44% for the lower part of rectus abdominis

  • 14-73% for the external obliques

  • 16-47% for the internal obliques

The second best exercise for abs: pike

The worst effects were during exercises, like “marching sitting”.

The biggest work of latissimus dorsi was in pike, skier, lifting knees sitting on a ball, moving hips supporting legs on the ball, extending hips to the right and left, and during push-ups (17-25%). The weakest work of this muscle group was during “marching sitting”, crunches and crunches to the knees (7-8%).

Rectus femori was best activated by extending hips to the left (35%), the least by crunches, roll-out and push-ups with legs on the ball. The muscles of lumbar spine were poorly activated in all the exercises (<10%).

The most important conclusion: rectus abdominis functions as a whole. Many people think that some exercises engage only the upper or only the lower part of this muscle. It's not true. According to the study, both, the upper and lower part of rectus abdominis worked as a whole with only slight difference in electrical activity.

Final conclusions:

  • balls can be a great tool to train abs, although you have to pay attention to the inefficient exercises promoted on the Internet (e.g. A6W, ABS),

  • press, squats and other classic strength exercises are worth doing mainly on stable surface – it's more efficient and safer than working out on a ball,

  • crunches and crunches to the knees can be ineffective tools of improving abs,

  • in one of the previous researches the best exercise for abs is the scissors – it's very similar to roll-up and pike – more at

Sources: 1. Electromyographic response of global abdominal stabilizers in response to stable- and unstable-base isometric exercise. 2. J Strength Cond Res. 2010 Jun;24(6):1537-45. doi: 10.1519/JSC.0b013e3181dc4440 Electromyographic analysis of upper body, lower body, and abdominal muscles during advanced Swiss ball exercises. 3. J Orthop Sports Phys Ther. 2010 May;40(5):265-76. doi: 10.2519/jospt.2010.3073. “Core muscle activation during Swiss ball and traditional abdominal exercises”.