Does the size of your balls matter?

Well? Does it matter?
Obviously you know that I am talking about stability balls, or exercise balls. You know those huge balloon like pieces of rubber rolling around the gym.
I find this topic to be fascinating and a great representation of how non-information gets passed off within the fitness industry. How big should your ball be?
You will hear a plethora of opinions on this. They should be as high as your waist when standing, when you sit on the ball your knees should be bent at 90 degrees, or they should be a certain size based on your height. Which is the right way? How can you ensure that you will be safe and not hurt yourself when choosing an appropriate ball size?
Choose one that you can’t fall off. That would be a good place to start.
Although, the very nature of the ball makes this difficult to accomplish as it is round. Manufacturers attempt to get around this by placing their balls into some kind of holder or frame, which is pretty illogical if we accept that the purpose of the ball is to create instability. Doesn’t placing you ball in a holder or stand defeat that entire purpose?
Alas, I digress.
How do you choose the size of your ball when there are so many differing opinions? Especially as those opinions all purport to be based on scientific fact. The answer?
I have no idea.
Nope. Over ten years training, a master’s degree in human movement and sport conditioning, trainer of athletes and weekend warriors and I have no idea how big your balls should be. How can that be?
Well, it’s simple really. There aren’t any perfectly sized balls out there. Different ball sizes are appropriate for different situations and can vary according to skill level. The truth is that there is no research or evidence that points to a specific size of exercise ball for a specific individual.
There are people reading this who might think I am way of my rocker (fallen off my ball?) and they have a system. I used to think this as well. I abided by the rule that your knees should be flexed at 90 degrees when you are sitting on the ball.
Then one day I started to ask why? (People who know me will recognize that I do this a lot – a lot). Somehow at my studio we have ended up with all one size of balls, 55cm. And they look a little small to be 55cm. What have we found? No increase in injuries from everyone using the same balls. No change to performance or strength. Definitely some people find different sizes more or less comfortable, but even that is more dependent on positioning or form on the ball.
According to all of my fellow fitness trainers ideologies I should be seeing all sorts of issues. Yet these haven’t materialized. This is what got me thinking, why does the size of your balls matter?
I don’t really think it does. At all.
And those who don’t agree and start citing all sorts of anecdotal beliefs I can use the rules of exercise and physics to present a case for ball size too.
If we assume that we use exercise balls to decrease stability in order to increase muscle activation through the core and challenge the body by forcing it to balance then technically the smaller the ball the better. The smaller the ball, the less surface contact between the ball and the ground, the smaller the surface contact point the less stability the ball has (the more it can roll around) and thus it will require more balance and more muscle activation through the core to stabilize the movement.
Based on this completely sound science you should always use the smallest ball possible that you can safely perform the exercise on. Regardless of your height, weight, or biomechanical design.
This doesn’t make sense. What about your 6’6” 250lbs athlete? Or your 5’0” 250lbs obese exercise newbie? He needs more of a challenge (so less contact with the ground smaller ball) and she would need less challenge (more ground contact largest ball). Neither of these individuals would feel comfortable in either situation. Albeit the science is perceivably sound.
What am I getting at?
The stability ball is a tool used within workouts. There is no science as to what size it should be. You should use whatever one feels comfortable and allows you to safely perform the intended exercise. That is all there is too it. Period.
The point of all this?
1. That it is about comfort not rules.
2. So called ‘rules’ that you may have heard in the fitness world don’t necessarily exist. Question everything, ask for evidence, and look for precedence.
The conclusion? It doesn’t matter what size your balls are as long as you are comfortable using them.
-Strength Coach Taylor

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