A foam roller may look sweet and innocent, but the effects it has on your body are far from that. You may have seen a few of of them lying around your gym:
Foam rolling is a form of stretching called myofascial release. The specifics of this type of stretching can get complicated, so I'll do my best not to get too scientific on you. Basically, what it does is help release the tension in your muscles, allowing them to loosen up and remain limber.
Think one word: massage.
Wanna know how how this seemingly simple piece of equipment does this? Think back to middle school science class. Do you remember your teacher mentioning something called the Golgi tendon organ? It may have seemed insignificant to you then, but this awesome little sensory organ is responsible for sensing tension and the rate of tension change in a muscle. When the Golgi tendon organ senses high or prolonged tension on a specific muscle, it responds by making the muscle spindles relax, releasing the tension and making that area looser and more limber.
The foam roller allows you to use your own body to put high and prolonged tension on a specific area of your body that may be sore or tight, activating the Golgi tendon organ and thus, relaxing the targeted muscle.
Pretty neat, huh?
So, next time you're in the gym, flag down a trainer and ask how to use a foam roller. I guarantee you, you'll see the difference.