There are two primary principles that govern the practice of Active Isolated Stretching (AIS). The first is to involve your nervous system in the stretch by taking advantage of reciprocal inhibition. What this means is that in order to move one way, your nervous system automatically shuts off the muscles that do the opposite motion, thus allowing for easier elongation of muscle tissue. You will actively contract the muscles that do the opposite motion of the muscles you want to stretch.

The second principle is to repeatedly stretch for 1.5-2 seconds at a time. Holding a stretch for longer stimulates a protective reflex, the stretch reflex, in which a muscle contraction is instigated to guard against injury. By not violating the body's natural protective mechanisms, a gentle, yet effective, stretch is achieved without causing the body to fight itself.

When the tissue is brought to tension, you gently apply 6-10 ounces of additional pressure to elongate the tissue a little further with each repetition. While you might not get much increase in range with simply one repetition, the little increases add up and over time, a more significant gain in flexibility can be noted.

With repeated active movements, you encourage greater blood flow than with a stretch simply held for longer periods of time. These movements also increase the communication between the nervous system and the musculoskeletal system, thus allowing for increased coordination, precision and improved physical performance.