Found this good article on Stretching on www.coreperformance.com; more specifically, related to "active isolated stretching" or assisted stretching.
Active Isolated Stretching
Sue Falsone January 6, 2009
Active isolated stretching (AIS) will help you bolster your flexibility and retain the gains you've made. In AIS, you don't hold a stretch for 10 to 30 seconds as you would in traditional stretching. Instead, you use a rope to gently assist in pulling your muscle a little farther than your body would ordinarily allow. This form of stretching reprograms your brain and your body to remember new ranges of motion, so you see fast improvements in flexibility.
How It Works
To understand how AIS works, try this fast exercise: Curl your arm up without any weight and squeeze your biceps at the top. Now try to flex your triceps. The reason your triceps is mush in this position is because of a scientific principle known as "reciprocal inhibition." Reciprocal inhibition states that the muscle on one side of a joint must relax in order for the opposing muscle to contract, and it's the basis of AIS.
"Often times, people stretch one day only to feel just as tight the next," says Sue Falsone, director of performance physical therapy for Athletes' Performance. But with AIS, Falsone says, you utilize reciprocal inhibition to not only loosen up the opposing muscle, but also increase your range of motion. You won't stretch for 10 to 30 seconds, as you would with traditional stretch-and-hold stretches. Instead, by holding stretches for just a couple seconds, you'll increase your range of motion with each repetition.
By using a rope to assist with the stretch, you can increase your range of motion by 6 to 10 degrees more than without the rope. This is key because it helps reprogram your brain to remember this new range of motion. That way it can remind your muscles the next time you stretch or play or lift weights.
Mind Over Muscle
Mentally you’ve conditioned yourself to believe you can stretch only to a certain point. And most often, you've determined that point because you're weak in a given area or you lack focus. With AIS, you're reprogramming your brain, along with any preconceived notions about your flexibility.
For example, say you’re doing a hamstring stretch. You’re lying on your back with a rope wrapped around one leg. First, you squeeze your quadriceps, hip flexors, and abs. As you squeeze, they contract, and your brain sends a message to your hamstrings telling them to relax. That enables you to gently assist with the rope to pull your hamstrings into a slightly deeper stretch, and it helps to reprogram your brain to recognize that new range of motion.
Since your quadriceps and hip flexors are doing the work, your brain is sending signals to your quadriceps, shutting off the signals to your hamstrings, which want to resist. In a sense, you’re tricking your body, and you're constantly reprogramming it.
When to Do It
If you have a tight back or hamstrings, you might find it valuable to practice AIS every day. It's best performed at the end of a workout or when you have some free time at night or on the weekends.
■Move actively through the range of motion and exhale as you gently assist with the rope.
■The rope should add no more than 6 to 10 percent to your range of motion.
■To save time, do the entire series of leg stretches with one leg first, then the other.