Stable Environments Yield the Best Strength Gains

All else being equal, the stronger, faster athlete will always win. This concept holds true for virtually every level of every team sport… and a few singles sports as well. Knowing this, why do coaches and trainers constantly place their athletes in unstable environments and expect them to get stronger?


Much ado about nothing has been made in recent years about the need for “core strength” and “core stability”. It is not uncommon to see someone in the gym standing on a Bosu ball doing 50 light dumbbell curls. This type of “training” has become the priority and the new norm at the sacrifice of actually producing tangible results. It has almost gotten to a point where having athletes pick up a barbell makes you a relic and considered “too dangerous” or “too resistant to change” to be relevant to modern strength and conditioning. Somehow, acting like a circus bear in the gym will get you to the next level.
Here is why that line of thinking is wrong.
Here’s a couple scenarios broken down using logic and physics. Stay with me, there’s bound to be some math involved.
We want our athletes to be faster or have speed. In sports, covering distance quickly is speed. In order to have speed, your body has to produce power. Power is a product of force and the velocity of the force produced. In other words, to cover ground, you have to transfer force into the ground quickly to over distance faster. The principle of Specific Adaptation to Imposed Demands (SAID) states that the human body adapts specifically to the types of demands placed on it. The ground is stable. In light of this, which do you think is more specific to sprinting ability: squatting on a lifting platform or squatting on a BOSU ball? These athletes aren’t running on a Nerf field made of foam. They are transferring force into a hard, often unforgiving ground. As coaches and trainers, we’re doing them a disservice by not replicating as much of the environment as possible.
Still not sure? I’ll raise you another scenario.We want our athletes to build muscle so they can get stronger. In order to get stronger, their bodies have to be exposed to a stimulus greater than it’s used to experiencing on the field. This is done by producing force greater than a resistive load (F) against acceleration due to gravity (9.81 m/sec²). Stay with me while we do some math. Our case study is a male who weighs 200lbs, about 120lbs (55kg) of which is used as his bodyweight resistance. He performs a bodyweight squat standing on a BOSU ball from a femur-parallel depth, producing ≈540 N of force in the process. Next, he loads up the bar with 315lbs (143 kg) and has to produce 1,942 N to squat from the same depth. Which load do you think will require greater adaptation from the body? Keep in mind that we didn’t even cover the amount of kinetic energy lost by squatting off the ball.
Don’t get me wrong. I don’t like to say “never” and these unstable implements can be used to great effect when incorporated into the program properly. Your body uses certain sensory receptors called proprioceptors to achieve balance. During the prime lifts, in order to move the most weight, your exercises should be bilateral and stable. However, during the accessory portion of the lift, instability training can be a fantastic tool when paired with unilateral exercises to work contralateral muscle groups in order to maintain joint stability. The BOSU ball, for example, is fine for improving knee stability during lunges. This isn’t where I have the problem. The issue lies when the priority is given to the unstable surface. The examples I gave above were unilateral exercises. If you think the next step to increasing squat difficulty is to remove stability, you should probably put more weight on the bar. That will be plenty difficult enough.
Enough with the core. Your core, or basically everything but the arms and legs, is trained in some capacity during each and every exercise, i.e. the squat, bench, deadlift, clean, lunge, etc. You can’t do an efficient bench press without scapular stability and stiff trunk muscles. There’s no way our case study subject can squat 315lbs without strong spinal extensors and effective pelvic stability. Whether you know it or not, as long as you’re performing the exercise correctly, you train these aspects every day. Sure it’s great to finish your workout with some targeted core work and unstable implements can be a good tool for this. That’s no different than finishing off your legs with some lunges when you’re done with the heavy squats. However, making balance and stability the focal point of your athlete’s training program by creating as much instability as possible at the expense of load is a quick way to see no results. Who do you think will win in a head-on collision: the guy squatting 315lbs or the guy that does Pilates 5x a week? If you answered the latter, you might be living in a fairy tale where all contact has been removed from sports and NFL teams lift teddy bears instead of weights in the off-season.
You will always be able to produce more force from a stable environment. So if your next thought is, “why not just do barbell squats on a BOSU ball? Then I’m getting the best of both worlds!”, I’ll remind you that the more force you can produce, the better off you’ll be and you certainly won’t be able to produce as much on the ball. Don’t believe me? I’ll invite you to to take a whack at your 1-rep max standing on that thing. Try not to fall on your face. I’ll wait.

Coach Runner is the Owner and Director of Sports Performance at Full-Stride Performance. Prior to founding FSP, Runner was formerly the Strength & Conditioning Coach for the Atlanta Gladiators of the East Coast Hockey League, a minor league affiliate of the NHL's Boston Bruins. Coach Runner was also the Head Strength & Conditioning Coach for the Husson University Eagles, Graduate Assistant Strength Coach at the University of Maine, and a former collegiate hockey player for Plymouth State University. He earned his Master of Science degree in Kinesiology & Exercise Science from the University of Maine and is recognized as a Certified Strength & Conditioning Specialist by the National Strength & Conditioning Association in addition to numerous other certifications.

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