You have little things in your muscles called muscle spindle fiber. They tell your brain how long your muscle is. If your muscle stretches too far, your muscle spindle fiber tells the brain, and the brain tells the muscle to contract (tighten).
The goal of stretching is to convince the brain that it’s OK to go past where it feels comfortable. If this happens, you can stretch the muscle further before it tightens.
Theoretically, this is how stretching should work, but is that actually the case? Research shows that stretching works, for a few minutes. Let’s say you stretch before your workout. You do a few muscles like the hamstrings, quads and glutes. You hold each stretch for 30 seconds to a minute, following proper stretching protocols.
After your stretch, you stand up and feel limber and more flexible. Your stretches worked! Your muscles can now go further without tightening, your brain has been convinced to let them lengthen. Then, you walk around the gym, read your program, and start your first exercise.
Let’s say you do kettlebell swings. Your muscles start to work, they contract and relax rapidly to lift the weight. After a few minutes, your muscles are starting to tighten up again and the effects of the stretching have been reversed.
Stretching works for a little, but the results don’t last. If you were to stretch after your workout, all the flexibility you gain will likely be gone by the time you walk out the door. That’s because stretching works on the nervous system, but it doesn’t physically lengthen the muscle. It just convinces your brain to relax the muscle for a little bit.
This relaxation can’t last, because eventually you’ll need to move the muscle again. Research shows that if you want to make lasting changes from stretching, you’d have to do it multiple times per day, every day, for at least a month. That’s a lot of stretching!
Your brain keeps a map of the body. It knows where your joints are and how long each muscle is. It sets limits on how long each muscle should be, and tightens them when a muscle exceeds that limit. It’s almost like you’re changing a setting in the brain. However, your brain will go right back to its default setting once you get moving again.
Not all hope is lost. You can increase your range of motion, and you should, before you workout. That’s why we stretch before exercise. Increasing your range of motion before you workout helps you get into positions that might otherwise be uncomfortable or dangerous. A combination of foam rolling, stretching and active warm-ups to raise the temperature of your muscles works best.