153 | Why Mobility Matters for Hypertrophy or Strength Gains

The FITSPRO Podcast

Mobility came on the fitness scene in large thanks to CrossFit. Perhaps you disagree or perhaps that is even untrue. But in 2011-2013 CrossFit was booming and thus came a large demand and need for mobility in the fitness industry. People like Kelly Starrett with Supple Leopard, and resources like ROMWOD mobility became more advisable than ever (from my experience and perspective). To my knowledge, mobility has been an important part of sports like weightlifting for decades. But was not as aggressively integrated into general strength training. Here’s the deal, mobility is, in short, your active range of motion. This is in contrast to flexibility which is your passive range of motion. Sitting in the middle splits is your passive range of motion, while sliding down into and back out of the middle splits is your active range motions. Can your muscles get you into and out of your end ranges? As you can imagine from these definitions, flexibility is the potential for mobility. For instance if you can’t get there passively, then you more than likely won’t be able to get to or past that point actively. Why does all of this matter for putting on muscle and/or gaining strength? I am guessing you’ll have more questions after listening to this podcast than when you came into it. But I don’t think that’s entirely a bad thing. I will do my best to keep it clear and concise, providing disclaimers where needed. I say that because this is not black and white. So, stay curious, and keep context in mind as we move forward. For starters, it comes down to muscle fiber recruitment. One could think of range of motion as the practical use of mobility within weight lifting. Range of motion is simply the distance traveled from start to finish of an exercise. Are you lowering all the way down in pull ups, are you squatting ass to grass? These would be considered FULL range of motion (or ROM). I hope you can see that if you lack mobility in a given area, you may be limiting your potential range of motion in a given lift. This is not the end of the world, most people have mobility restrictions and can still put on plenty of muscle. I don’t wish to scare you or over complicate this. Why does range of motion matter for strength or hypertrophy? We answer these questions because they CAN BE connected. Muscle mass is the potential for strength. Muscle is the how the body will eventually demonstrate strength (force production). So now we ask how we build muscle. As discussed on many episodes, there are three main factors - being mechanical tension (this is most important), metabolic stress, and muscle damage. We will be thinking about mechanical tension and maybe muscle damage. For a muscle to contract, muscle fibers are recruited. Number of muscle fibers recruited and strength of a contraction are positively correlated. Meaning more fibers = higher contraction. This is what we are after both for strength and hypertrophy. That is also where range of motion comes in. Within range of motion, the muscle is lengthening - this is known as the eccentric phase. That means the shortening phase only has to contract within the range the muscle was lengthened. That also limits the fibers which are recruited. More range of motion has the potential to mean MORE FIBERS recruited. And that means more potential mechanical tension and muscle damage. Ideally, with proper load, recovery, and diet, muscle cell growth or strength gains. Think about body building and the idea that they want to stress a given muscle from as many angles as possible. The literal point of this is to maximize motor unit recruitment and fatigue. The same applies here. More range of motion or improved range of motion could mean more fibers working. Remember I said this was not black and white. Just using full range of motion in the absence of a load challenging enough to stimulate the muscles is not going to equate to more muscle or strength.