The use of foam rollers and lacrosse balls for "soft tissue release" have become very common and for good reason. Most people are familiar with their benefits but not necessarily the science behind WHY they work. Here's a brief explanation of why these tools can be helpful and how to properly use them.
We all have specific receptors in the skin and on other organs called "mechanoreceptors" that detect sensations in touch. They are designed to detect mechanical sensations of differences in pressure. There are various types which respond to different forms of stimuli and produce different results.
Type 1 and 2 which include muscle spindles, golgi tendon organs, pacini corpuscles, and ruffini endings respond to pressure, strong changes in length/stretch, vibration, and high velocity thrusts (joint manipulation). When stimulated these cells respond by decreasing muscle tone or "tightness."
Examples of stimuli: active (not passive) stretching, percussion therapy (DMS instrument), manual therapy such as Active Release Technique, Chiropractic adjustments.
Type 3 and 4 which are made up of interstitial receptors which respond to rapid as well as long, deep, sustained pressure changes onto the tissues. This actually has a unique affect on the Autonomic Nervous System which is the system that controls blood pressure, respiration, and digestion. Stimulation of these fibers can reduce overall muscle tone as well as improve oxygen and blood flow to tissues by increasing vasodilation and changing tissue viscosity and fluid dynamics.
Examples of stimuli: manual therapy/fascial work/bodywork, soft tissue release via foam roll or lacrosse ball.
Soft tissue release is a great way to significantly reduce pain and trigger point sensitivity. When combined with active stretching can help improve range of motion and joint mechanics.