For most of us, it may not be bigger muscles.
Why do we lift weights? Is it to increase strength? Power? To get buff? Whatever your goal is for your resistance training program, it’s important to understand the mechanisms of strength gains.
Our skeletal muscles contract voluntarily. That means our brains have to pass a signal down our spinal cord and out through a motor neuron – or the nerve that connects your muscle to your spinal cord – in order to produce movement. This is the same whether you’re using two muscle fibers to crack a smile, or two thousand to do a back squat. And when we lift weights or do any type or resistance training, we’re forcing our nervous system to find the best possible way for our muscles to move a mass. Over time, we improve the connection between our skeletal muscles and our brain. Our muscles get smarter.
If you’re a coach or a trainer, you see this all the time in your new athletes. For example, let’s say the first day you do a set of bench press, your brain recruits one hundred muscle fibers. Next time, you’ll recruit one hundred-fifty. 150 fibers can produce more force than 100. The second time around, there’s less shaking; the movement is more controlled, with less wasted energy to move the weight.
It takes just one bout of resistance training to start to see these neural adaptations. We improve our balance, our coordination of antagonistic muscle groups, as well as our muscle fiber synchronization. All these adaptations allow more efficient movements: producing greater force at an increased rate, and applying that force more effectively. Ever heard of “old man strength”? That’s a real thing! While we lose the ability to build bigger muscles as we age, our nervous system adaptations persist as long as we do resistance training. That means that while you may look your strongest in college, you may actually be stronger in your fifties due to improved muscle coordination.
Another cool adaptation that allows us to get stronger is the removal of neural inhibition. Our nervous system is naturally a little cautious when we’re resistance training to keep us safe from injuries. It takes a bit of training to teach our nervous system that it’s okay to produce more controlled forces. Ever heard of the mom that lifted the car off of her child? That’s a real thing too! And it’s not because she had twenty-inch biceps!
One of the classic experiments that provided the evidence for “neural dis-inhibition” involved college students performing a shoulder press one time in complete silence, and another time with a distraction. Max force was measured during both trials to see if the distraction could make a difference. But it wasn’t just some encouraging words to distract the subjects; a researcher stood behind each subject and fired a blank shot into the air from a revolver. And guess what they found? More force production with the distraction from the gun. However, we wouldn’t recommend that for every gym.
Improved coordination and muscle fiber recruitment are also especially important for injury prevention. Both overuse and underuse (i.e. sitting) injuries often result from the inability to recruit the little muscles that stabilize our joints and allow the big muscles to move correctly.
So what about getting those bigger muscles? If hypertrophy – or increasing the size of muscle fibers – is your goal, you must recruit those muscle fibers. If you can recruit more muscle fibers to produce force, those fibers can start to get a little bigger. The opposite happens when you break a bone or get surgery: when you can’t recruit a muscle fiber to move it, the muscle gets smaller.
Anyone can increase the size of a muscle to a certain extent, but hypertrophy depends on many factors. It requires the right nutritional status (think lots of protein consumption at the right time), the right hormonal environment, and especially the genetic capacity to get bigger. That may not be the most realistic goal for every single person.
But a healthy nervous system will adapt to resistance training every time, no matter what.
So whether you’re trying to dunk a basketball, get to a higher gear on the bike, or finally beat your dad in arm wrestling, remember that getting stronger isn’t only about getting bigger muscles.