It’s called self-myofascial release. By applying gentle force on a "knot", the elastic muscle fibers are altered from a bundled position into a straighter alignment and into their proper direction. The way to do this is to find the tender spot on your muscle that has the "knot" and hold for about 20-30 seconds, or until discomfort is reduced. This will help restore your body back to it’s optimal level and you’ll feel great and re-energized afterwards.
You can purchase foam rollers now at most sporting good stores and of course online at sites like Amazon.com. Price ranges are typically about $15-$25.