There are several different types of stretching. The methods described below will help you safely improve your level of flexibility. The two most common and accepted techniques for improving flexibility are static and PNF stretching.
Static stretching is a low-force stretch where the muscle is held at the greatest possible length for up to 30 seconds. This is probably the most common type of stretch, mainly because it benefits from being both effective and safe. SparkPeople’s Stretching Demos are all examples of static stretches.
PNF is short for Proprioceptive Neuromuscular Facilitation. This involves maximally contracting a muscle (usually with a partner or trainer who is trained in this technique) and then immediately doing a static stretch for the muscle. This type of stretching may be performed without a partner, although it is usually more effective with a partner's assistance. In all cases, it is important to note that the stretched muscle should be rested (and relaxed) for at least 20 seconds before performing another PNF technique. There are two types of PNF stretches, Contract-relax (an isometric contraction of the muscle, followed by relaxing, then stretching to the point of limitation) and Contract-relax-agonist-contract (an isometric contraction of the muscle, followed by relaxing, stretching to the point of limitation, then contracting the agonist/opposing muscle, followed by a stretch to the point of limitation).
Passive stretching increases the range of motion by using an external force (like a partner, a wall or the floor). These stretches can be very useful in the development of stretching but care must be taken to ensure the stretch is not forced; it should remain within the realms of comfort at all times.
Active stretching involves assuming a position (or stretch) and then holding it there with no assistance other than using the strength of your “helper” muscles. When you lie on your back with one leg extended up in the air, for example, and continue to hold it there without any assistance you are doing an active stretch. Active stretching increases active flexibility and strengthens the “helper” muscles too. Active stretches are usually quite difficult to hold and maintain for more than 10 seconds and rarely need to be held any longer than 15 seconds. These types of stretches are frequently used in yoga.
Dynamic stretching involves controlled, gentle leg and arm swings that take you to the limits of your range of motion. There are no bounces or "jerky" movements. An example of dynamic stretching would be slow, controlled leg swings, arm swings, or torso twists. Dynamic stretching improves dynamic flexibility and is quite useful as part of a warm-up for an active or aerobic workout (such as a dance or martial-arts class).