According to the American Council on Exercise, stretching is an integral component of fitness and should be a part of any workout program. The act of stretching elongates muscles and increases the body’s range of motion. Additionally, scientific research indicates that stretching encourages muscle growth.
A study published in the "Journal of Applied Physiology" in 1993 discovered that stretching can indeed enhance muscle growth. In the study carried out by University of Texas researchers J. Antonio and W. J. Gonyea, 26 adult quails increasingly had their wings stretched over the course of 38 days with weights ranging from between 10 and 35 percent of their body weight. At the end of the experiment, the birds were dissected, revealing as much as a 318 percent increase in muscle mass after 28 days when compared to a non-stretched wing.
"Muscle & Strength magazine" writer Doug Lawrenson states that stretching can be divided into seven categories: ballistic, dynamic, active, passive, static, isometric and proprioceptive neuromuscular facilitation, or PNF. Ballistic stretching is when you bounce in and out of the stretch and should not be used. Dynamic, active, passive and static stretches employ a smooth stretching motion that relaxes muscles and prevents fatigue. Isometric and PNF use contractions while stretching to encourage maximum muscle growth.
During an isometric stretch, you apply resistance to your body and then flex your muscles in opposition to that resistance without moving the body part. An example of an isometric stretch would be to grab the ball of your foot with one hand and then attempt to straighten your ankle by stretching your calf muscle.
PNF stretches are carried out by applying resistance against a stationary object similar to an isometric stretch, relaxing the resistance to increase the depth of the stretch and then applying the resistance again. An example of this type of stretch would be to lie on your back and have a partner place his shoulder underneath your knee and push your leg toward your chest. You then flex your hamstring and push against the resistance provided by your partner. After the resistance period ends, you relax your hamstring and your partner increases the depth of the stretch before another PNF stretch is begun.
Stretching reduces muscular tension, which can inhibit your muscles’ ability to grow after being exerted. It also increases the mechanical efficiency of your muscles, meaning that you will require less energy when exerting yourself and can thus execute more repetitions in your strength-training routine with the same amount of energy. Finally, stretching improves the blood flow to your muscles, which increases the delivery of essential nutrients and decreases the build-up of lactic acid, which causes soreness and fatigue in the muscles.
Each stretch you execute should be held between seven and 15 seconds after reaching the point of maximum stretch. It's common to take 30 to 60 seconds to ease into the maximum point of stretching. For the best results in muscle growth, both warm-up and cool-down periods of five to 20 minutes of stretching should be engaged in before and after every workout.