There are many instances in daily life and sport in which force must be exerted when an individual performing the task is in an unstable condition. Stability balls (also called Swiss Balls) are used as a platform for training to provide an unstable environment for force production. Here you will get the basics.
The increased stress associated with instability has been postulated to promote greater neuromuscular adaptations, such as decreased co-contractions, improved coordination and proprioception (sensation of joint movement and joint position), and confidence in performing a skill. High muscle activation with less stress on joints and muscles is especially beneficial for general musculoskeletal health and rehabilitation.
Stability ball training also has a strong relevance for athletes. To understand the benefits of stability ball training, one must understand that the body functions together as a unit. While some muscles contract to produce movement, others contract to help balance the body and stabilize the spine. Still, other muscles will kick in each time the body recognizes a shift in position, to correct a loss of balance. The body is a linked system that works together to coordinate athletic actions like throwing a ball, when squatting and bending over.
Instability decreases the externally-measured force output and strength of a muscle while maintaining high muscle activation. Thus, for exercises performed on a stability ball versus on a stable surface, while there is a decrease in strength (less weight can be lifted), there is no significant difference in overall EMG activity between the stable and unstable protocols (1). The high muscle activation of limbs and trunk when unstable can be attributed to the increased stabilization requirements. The decreased strength (force output) for exercises performed on a unstable device can be attributed to the decreased balance on the ball, which forces assistive limb muscles to play a greater role in joint stability and in performing the exercises on the ball (1).
Stability ball training is perfect for children. Balls are not only playful; stability ball training at an early age helps develop coordination and body awareness, and sets the stage for future success in athleticism. Stability balls are also easy to travel with and perfect for a hotel room workout since they don’t take up much space.
When implementing a resistance training program for musculoskeletal health, rehabilitation or sports performance, 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 (2).
While stability ball training can benefit everybody who does not suffer from any injuries, obese individuals are more challenged by movement and have less balance and coordination. They can do better by starting out training with weight stack machines and cardiovascular training, and then successfully implement stability ball training into their routine. Also, people who are just starting out to exercise need to build up at base strength level (especially spinal stability) before they can accept exercises that will challenge the core. Also, individuals with recent/acute injuries or chronic low back pain should be careful with stability ball exercises, and consult with a physical therapist.
To wrap up, stability ball training is useful for all non-injured populations, of all ages, because it can be easily adapted to meet a variety of needs and goals (it is the how, when and how much the stability exercises are used in a training program that vary depending on the needs and goals of the individuals).
1. Anderson KG, Behm DG. Maintenance of EMG activity and loss of force output with instability. J Strength Cond Res. Aug 2004;18(3):637-640.
2. Behm DG, Anderson KG. The role of instability with resistance training. J Strength Cond Res. Aug 2006;20(3):716-722.