Training on an unstable surface or platform is popular these days. Rather than planting both feet firmly on the ground when strength training, you instead stand or sit on an unstable surface such as a stability ball, a dome, balance board, or wobble board. Manufacturers of these products profit when people add these items to their strength-training arsenal, but how effective is training on an unstable surface and does science support its benefits?
Whether training on an unstable surface is the best approach depends on your training goals. Physical therapists often use them in therapy sessions for rehabilitation. If a person has injured an arm or a leg and loses some function, training on an unstable surface can help retrain the muscle and restore healthier neuromuscular activity. Instability training also helps rebuild healthy kinesthetic sense and proprioception.
In addition, unstable training forces the core muscles that stabilize the pelvis to work harder. This builds greater core strength and stability. Therefore, training on an unstable surface has benefits, but it’s not the best approach for gaining strength and power. Here’s why.
Strength Building and Unstable Surfaces
To build muscle strength, you must subject your muscles to progressive overload. Over time, you challenge them with greater resistance, so they’re forced to adapt and become stronger. If you’re standing on an unstable surface such as a dome, however, you won’t be able to train with as much weight as when your body is in a stable position.
For example, do a set of squats on the floor and again on a domed surface and you’ll find that you can’t use as much resistance and still maintain good form. The inability to handle the same amount of weight can interfere with strength gains. For maximal strength gains, you must lift at a high percentage of your one-rep max. That would be tougher to manage on an unstable surface.
Not only that, but training on an unstable surface impedes power gains. You build power by moving a weight or other form of resistance explosively. It’s harder to generate explosive force when you’re on an unstable surface, and it’s risky in terms of injury too. Explosive movements carry a higher risk if you don’t use impeccable form and an unstable surface magnifies the risk.
What Research Says about Training on an Unstable Surface
In one study of soccer players, researchers at the University of Connecticut compared the impact of doing lower body exercises on an unstable surface and a stable one, the ground. The players who did the exercises on an unstable surface experienced less of an increase in power capabilities relative to those who did the exercise with both feet on the ground.
Another study that compared the isometric force developed during a chest press on a stable and unstable surface found that force generated dropped by 59% when subjects did the exercise on a stability ball. These studies suggest that unstable surfaces aren’t ideal for building strength and power, as force production is reduced.
Alternatives to Unstable Training
If your goal is to boost core strength and stability or improve functionality, training on an unstable surface is appropriate, but it falls short when the goal is strength or power gains. If that’s your goal, traditional training on a stable surface such as the ground is more effective.
An alternative to training on an unstable surface is unilateral exercises, where you train one side at a time. For example, one-legged squats and deadlifts provide an instability challenge that activates the core muscles more than bilateral exercises where both feet are on a stable surface. Unilateral exercises are also useful for correcting muscle imbalances. Once you identify the weaker side, you can focus more on building strength on that side.
You wouldn’t want to do all unilateral training as you still may not be able to use as much resistance for certain exercises when you’re training one side at a time. For example, it’s much harder to do a one-leg squat and you may not feel comfortable using a heavy resistance when doing one. But there’s no reason you can’t include both in your strength-training routine, especially if you have a muscle imbalance between your two sides. Plus, unilateral training helps build greater stability, coordination, and fine motor control.
It might surprise you to learn that when you perform unilateral strength exercises, it also boosts strength on the opposite side, the side you’re not working. This is because of a phenomenon called cross-education. It works because working one side harnesses the same neurological pathways that stimulate the muscle on the opposing side. So, both sides make strength gains.
The strength gains are modest relative to the side you’re working, but it’s not insignificant. For example, studies show that cross-education can increase the strength on the non-working side by almost 8%. Physical therapists know this, so they may encourage their clients with an injured limb to work the uninjured side as doing so will help maintain strength on the injured side.
The Bottom Line
Unstable surfaces, like stability balls and domes, have their place in training and are effective for building core stability, but they aren’t the most effective for optimizing strength and power. An unstable surface limits the amount of force you can generate when you lift and makes it harder to lift with explosive force to build power. For strength gains, the name of the game is traditional training that employs progressive overload, and for power, a fast tempo, or almost explosive, tempo maximizes gains. It’s best to do both on a stable surface for the most benefits.
Still, you can include some exercises on an unstable surface to strengthen your core and build core stability, just don’t make them the mainstay of your workouts if you’re trying to become your strongest and most powerful.
References:
- J Strength Cond Res. 2009 Dec;23(9):2443-50.
- On Fitness. May/June. 2010. “The Limitations of Unstable Device Strength Training”
- Int J Sports Phys Ther. 2012 Apr; 7(2): 226–241.
- Eur JAppl Physiol (2002) 86: 287-294.
- Journal of Science and Medicine in Sport, 15(2), 94-101.
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