Let’s get one thing straight: balancing on a BOSU ball is not a badge of athleticism. Yet, I constantly see people in the gym doing squats or biceps curls on unstable surfaces thinking they're improving ankle strength, core function, or stability.
It’s a well-intentioned but misguided strategy. So, what does the research actually say about unstable surface training?
What Is Unstable Surface Training (UST) Really Training?
Unstable surface training—using tools like BOSU balls, wobble boards, or foam pads—adds instability to exercises, forcing the body to work harder to stay balanced. This does a few things:
Increases neuromuscular coordination demands
Engages the vestibular system and visual feedback
Activates postural muscles through reflexive adjustments
Requires greater core and small muscle engagement
Sounds like a win, right?
Not so fast.
The Ankle Stability Myth
Ankle sprains make up about one-third of all sports injuries, and the recurrence rate is shockingly high—up to 70%. A lot of this is due to poor proprioception—the body’s ability to sense joint position and movement.
So people assume that training on unstable surfaces improves proprioception and ankle stability.
But here's the problem: it doesn’t.
One study looked directly at proprioceptive training and found that exercises performed on unstable surfaces did not effectively improve proprioception or joint position sense. In other words, wobbling doesn’t equal proprioceptive adaptation (Wright & Arnold, 2012).
Strength Loss on Unstable Surfaces
Not only are you not improving ankle function—you might be compromising your strength, too.
A 2021 study found that grip strength and overall power output were significantly reduced when resistance exercises were performed on unstable surfaces (Zemková et al., 2021). That’s because your body’s focused on not falling over rather than producing force.
Another systematic review echoed this, concluding that unstable surface strength training has limited transfer to strength and power in stable, real-world conditions (Behm et al., 2015).
Translation: You’re getting worse at lifting and still not preventing that ankle sprain.
So What Should You Do for Ankle Stability?
There’s solid evidence that certain proprioceptive and strength training strategies actually reduce ankle sprain recurrence:
Controlled Strength Training
Calf raises (bent and straight knee)
Tibialis raises, toe walks
Split stance and single-leg exercises with tempo
Sensory-Motor Work
Eyes-closed balance drills on a firm surface
Controlled single-leg deceleration (hop and stick)
Multidirectional landing mechanics
Reactive & Perturbation Training
External taps or light band perturbations while holding position
Partner drills mimicking sport-specific movement
These strategies are rooted in actual performance and rehabilitation research (Schiftan et al., 2015), and more importantly—they help you move better, get stronger, and build confidence after injury.
Final Thoughts
Unstable surface training isn’t evil—it has its time and place, especially in rehab or return-to-play. But for most people chasing strength, resilience, or better ankle stability, it’s a poor substitute for well-designed, progressive training.
So unless your goal is to join Cirque du Soleil, maybe leave the BOSU ball alone.
Train smart. Get strong. Train. Play. Repeat.
References
Behm, D. G., Muehlbauer, T., Kibele, A., & Granacher, U. (2015). Effects of strength training using unstable surfaces on strength, power and balance performance across the lifespan: A systematic review and meta-analysis. Sports Medicine, 45(12), 1645–1669. https://doi.org/10.1007/s40279-015-0384-x
Behm, D. G., & Colado, J. C. (2012). Instability resistance training for health and performance. Strength and Conditioning Journal, 34(3), 33–48. https://doi.org/10.1519/SSC.0b013e31824f2552
Schiftan, G. S., Ross, L. A., & Hahne, A. J. (2015). Proprioceptive training for the prevention of ankle sprains: A systematic review and meta-analysis. Journal of Science and Medicine in Sport, 18(3), 238–244. https://doi.org/10.1016/j.jsams.2014.04.007
Wright, C. J., & Arnold, B. L. (2012). Fatigue and muscular performance during dynamic activities: A comparison of stable and unstable conditions. Journal of Athletic Training, 47(4), 407–416. https://doi.org/10.4085/1062-6050-47.4.16
Zemková, E., Jeleň, M., Čepková, A., & Uvaček, M. (2021). There is no cross effect of unstable resistance training on power produced during stable conditions. Applied Sciences, 11(8), 3401. https://doi.org/10.3390/app11083401