Core stability training on unstable devices

In many fitness centers people perform core stabilityBosu core stability training training to strengthen the so-called ‘core’ on unstable surfaces. Well known examples of these are the Bosu Balance Trainer, Bosu Ball (Both Sides Up) and the Swiss Ball. The core is usually defined as the region of the body which is made up by the abdominal wall, pelvic floor, the lower back and the diafragm. This region plays an important role in stabilizing the spine during movements and is therefore crucial in sports performance. In addition, a large percentage of low back pain cases are caused by badly functioning core muscles. The idea behind training on an instable surface is that more muscles are active to stabilize the body during any given movement compared with performing the same movement on a stable surface. This would result in improving intermuscular coordination and therfore reduce complaints caused by weak or badly cooperating muscles. Moreover it could result in better training results and in many sport activities improve performance. This article aims to review the scientific evidence for core stability training on unstable surfaces as a means to treat low back pain and as functional training to enhance sports performance.

Core stability training in fitness training

Instability trainers such as the Bosu BalanceCore muscles trainer and Swiss Ball are often used to strengthen the abdominal muscles (m. rectus abdominis,  m. obliquus externus and internus and the m. abdominis transversis) and the muscles of the lower back (m. erector spinae). This is often done with the same sort of exercises most peope use to strengthen their core without the aid of an instability trainer such as the crunch or back extension. According to a study by Vera-Garcia et al. (2000) which measured EMG activity of the abdominal muscles during crunches on a Swiss Ball and compared these with a regular crunch on the floor. During the crunch on the Swss Ball, the m. rectus abdominis was two times more active compared with the regular crunch. The m. obliquus externus even was four times more active to aid in stabilizing the movement. These results are in correspondence with studies performed by Petrofsky et al. (2007) and Behm et al. (2005), who concluude that exercises performed on an instability trainer are more effective in strengthening te core muscles than exercises on a stable surface. In light of the results in the studies above, it can be concluded that training the core muscles on an instable surface such as a Swiss Ball or Bosu Ball activates the muscles more strongly than on a stable surface and is therefore more effective.

Core stability training in low back pain therapy

One of the most common causes for low back pain lies in the coordination of the muscles that stabilize the spine. It would therefore seem logical that exercises that aim to improve this muscle coordination would be effective in reducing low back pain. According to a pilot study performed by Marshall & Murphy (2006), exercises perfromed on a Swiss Ball an effective method to treat low back pain. Carpes et al. (2008) found that it was effective to reduce low back pain and, in addition, it also improves walking patern and balance. Although both these studies were performed without a control group, the patients in both studies were suffering from low back pain for at least one year and on average 4,8 years. Therefore it is unlikely that the reduction in pain would be a result of a healing process instead of the exercises on an instability trainer. Another study performed by Marshall & Murphy (2008) did include a control group and it found that exercises on a Swiss Ball under supervision of a fysio therapist were more effective in treating low back pain than exercises performed on a stable surface. Put together, these studies support the use of training the core muscles on an instable surface to positively affect the course of lwo back pain.

Core stability training as functional training to increase performance in sports

Instability trainers pose a greater challenge for the neuromuscular system to execute movements correctly and therefore this form of training would be effective in enhancing sports performance. According to a study performed by Okada et al. (2011) there is no clear correlation between the ability to stabilize the spine and the quality of functional movements or sports performance. This is supported by a study by Wagner (2010) which could not find a relation between strength of the core muscles and sports performance in female soccer players. Their explanation is that when a sufficient level of stabilisation is reached, a larger force will not contribute any further to sports performance. Moreover, all these studies state that, in order to improve sports performance, training should simulate the sport as much as possible, because of the specificity of training effects.

Conclusions

Strengthening the core musculature with core stability training can effectively be performed on instable surfaces such as a Bosu Balance Trainer or a Swiss Ball. In addition it is effective in treating low back pain. However, its’ uses in improving sports performance are limited. When the core musculature is strong enough, no further improvements in sports performance will occur as a result of further increasing core musculature strength. It is more effective to choose for more sport specific or functional exercises to achieve further improvement.

References:

-Behm, D.G., Leonard, A.M., Young, W.B., Bonsey, W.A.,MacKinnon, S.N. Trunk muscle electromyographic activity with unstable and unilateral exercises. Journal of Strength and Conditioning Research, 2005a, 19, 1, 193–201.

-Carpes, F.P., Reinehr, F.B., Mota, C.B. Effects of a program for trunk strength and stability on pain, low back and pelvis kinematics, and body baance: A pilot study. Journal of Bodywork and Movement Therapies, 2008, 12, 22-30.

-Marshall, P.W., Murphy, B.A. Evaluation of functional and neuromuscular changes after exercise rehabilitation for low back pain using a Swiss ball: a pilot study. Journal of Manipulative Physiologic Therapeutics, 2006, 29, 7, 550-560.

-Marshall, P.W., Murphy, B.A. Muscle Activation Changes After Exercise Rehabilitation for Chronic Low Back Pain. Archives of Physical Medicine and Rehabilitation, 2008, 89, 7, 1305-1313.

-Okada, T., Huxel, K.C., Nesser, T.W. Relationship Between Core Stability, Functional Movement, and Performance. Journal of Strength and Conditioning research, 2011, 25, 1, 252-261.

-Petrofsky, J.S., Batt, J., Davis, N., Lohman, E., Laymon, E., De Leon, G.E., Roark, H., tran, t.M., Ayson, E.G., Vigeland, K.M., payken, C.E. Core Muscle Activity During Exercise on a Mini Stability Ball Compared With Abdominal Crunches on the Floor and on a Swiss Ball. The Journal of Applied Research, 2007, 7, 3, 255-277.

-Vera-Garcia, F.J., Grenier, S.G., McGill, S.M. Abdominal Muscle Response During Curl-ups on Both Stable and Labile Surfaces. Physical Therapy, 2000, 80, 6, 564-569.

-Wagner, J.S. Convergent validity Between Field Tests of Isometric Core Strength, Functional Core Strength, and Sport Performance Variables in Female Soccer Players. Boise State University 2010.