Is resistance training on unstable surfaces effective?

Instability training, or exercising while on unstable surfaces, has become both popular and controversial. Performing resistance training on unstable surfaces such as exercise balls, balance boards, stability disks, and foam pads has been shown to reduce force output, but increase activation of “core” muscles of the trunk (Behm and Anderson 2006). No studies, however, have directly compared training outcomes on stable and unstable surfaces.

In a paper published in the Journal of Strength and Conditioning Research, researchers performed a 7 week study of resistance training exercises in 2 groups: one using unstable surfaces and the other on stable surfaces. The researchers hypothesized that the instability resistance training group would demonstrate significantly greater gains in functional testing after the program.

Forty, college-aged, healthy untrained subjects volunteered for the study. Subjects performed squats and vertical jumps, as well as 3 machine-resisted upper body exercises:  lat pull down, butterfly, and bench press. Both groups performed upper body exercises at 70% of 1RM. The stable surface training group performed squats at 75% 1RM, and the instability group performed squats at 50% 1RM while balancing on wobble boards, stability discs, or a BOSU ball. The instability group also performed 4 trunk stabilization exercises on an exercise ball. Subjects were tested for leg extension strength, static and dynamic balance, sit-ups, long jump, hop test for time, shuttle run, and sprint.

After the 7 week training program, both groups improved in strength, balance, and function. There was no significant difference between the groups with the exception that the instability group had better performance on sit-up and hop tests.

While this study found that instability training was as effective as traditional stable training, it was interesting that the instability group had similar results even while training the lower extremities at 1/3 less resistance compared to the stable group. The authors suggested that resistance training on unstable surfaces keeps muscle activation high, even at reduced loads, because the muscles have greater stabilizing functions. The authors also noted that opponents of resistance training on unstable surfaces argue that instability devices are not necessary because balance challenges in daily life are sufficient; therefore, additional challenge is not needed. The authors also pointed out that experienced resistance-trained individuals may not experience the same benefits as the untrained subjects in this study.

In conclusion, the authors noted that resistance training on both stable and unstable surfaces can benefit inexperienced exercisers. To get the benefits of both types of training, Thera-Band® stability trainers, stability discs, exercise balls, and balance boards should be incorporated in resistance training programs.  The authors also suggest reducing the resistance and increasing the repetitions compared to stable surface exercises when performing training on unstable surfaces.

REFERENCE: Kibele A, Behm DG.Seven weeks of instability and traditional resistance training effects on strength, balance and functional performance. J Strength Cond Res. 2009 Dec;23(9):2443-50.

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