Unstable surfaces such as exercise balls, foam pads, and balance boards have been used in both rehabilitation and fitness exercise programs. These balance devices are often combined with resistance exercises; however, some researchers have suggested that using resistance with instability exercise (also known as “Instability Resistance Training”) requires some modification in exercise prescription.
While force output was found to decrease, Behm and Colado found that studies on electromyographic (EMG) output while exercising on unstable surfaces increases an average of 47%. They also reviewed the effects of balance training alone (without concomitant resistance training) on balance, proprioception, and function, finding an average of 100% improvement in balance and a 31% average improvement in functional performance. In addition, they reported that studies incorporating instability resistance training improved performance an average of 22%.
Behm and Sanchez made an interesting observation: “instability-trained subjects could exert greater forces when experiencing an unstable environment.” This suggests that in environmental situations such as a slippery floor or a muddy athletic field, instability resistance-trained individuals may have an improved ability to respond to perturbations and reduce injury risk.
While their paper was not a meta-analysis, Behm and Colado suggest that a balance training program is a safe “first step” in rehabilitation because it can still improve strength and muscle activation when pain, inflammation, and stiffness are present. At the other end of the spectrum, athletes need significant strength and power which may not be attainable during instability resistance training.
If the goal of resistance training is to improve strength and power output, unstable surfaces should not be used concomitantly with resistance. Instability resistance training incorporating unstable surfaces may be best utilized in rehabilitation and preventive exercise programs. Behm and Sanchez recommend using a moderate level of instability during instability resistance training because force output is decreased but EMG activation is not substantially affected. They suggest this moderate level would “allow the combination of lower external forces to be placed on recuperating muscles albeit with a relatively higher degree of activation.” Furthermore, instability resistance training may “play a strategic role in the prevention and treatment of low back pain.”
Finally, Behm and Colado suggest instability resistance training provides many additional benefits to improving motor control, which may also be important in rehabilitation and injury prevention:
- Higher trunk muscle activation
- Activation of feed-forward and feedback systems for postural adjustments
- Promoting agonist-antagonist co-contractions with shortened latencies for rapid stiffening and protection of joints
In summary, unstable surfaces such as Thera-Band Exercise Balls, Stability Trainers, and balance boards can be used with or without resistance for a variety of benefits including rehabilitation, fall prevention, and performance enhancement.
REFERENCE: Behm D, Colado JC. The effectiveness of resistance training using unstable surfaces and devices for rehabilitation. 2012. Int J Sports Phys Ther. 7(2):226-241.