Any foreign movement that requires a certain level of resistance is going to produce a favorable adaptation. So yes, even the application of an unstable surface (like the Bosu Ball), can increase the activation of specific stabalizer muscles.
HOWEVER, if your goal is to get stronger in the squat or overhead press (which it should be), or build more muscle in the quads and shoulders (which it should be), then it doesn’t.
A study from 2004 in the Journal of Strength & Conditioning Research found 59.6% lower force generation for the chest press on an unstable surface compared to a stable one.
In other words, there will be times when you may want to incorporate an unstable surface to apply additional resistance during a core exercise, or target a specific weakness elsewhere (ex: the knees), but never during a push, pull, bend, or extend. As the unstable surface means less force generated, (which translates to less strength development) while the increased activation of the core takes away from the stress placed on the primary movers (which translates to less hypertrophy).
Thus, although Bosu Ball squats may SEEM more challenging because your off-balance, squats on a flat stable surface are superior at building size and strength – because more force is generated.
Research from 2006 in the Journal of Strength & Conditioning Research found a 40-45% force reduction in the squat when performed on an unstable surface.
And if this is your goal (which it should be), lifting weights the traditional way is ideal.
Interestingly, even if this isn’t your goal, and ‘core activation’ is, heavier weights on a stable surface may also be superior – as was concluded in this study from 2010 in the Journal Strength & Conditioning Research:
“…Greater activation of the core musculature appears to occur by lifting a heavier weight overhead than by lifting a lighter weight overhead either with an unstable load or on an unstable surface.”
So, perhaps it’s time to barter with your Bosu? And maybe trade it in for some heavier weights?
Stay Lean!
Coach Mike
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