This is an excerpt from Women's Home Workout Bible by Brad Schoenfeld.
The goal of any flexibility program should be to achieve an optimal balance between mobility and stability within a functional range of motion. Just as a lack of flexibility can be detrimental, so can being hypermobile. As a general rule, a joint that is too flexible will be unstable; the associated muscles can't maintain joint integrity, increasing susceptibility to injury. As with most things in life, more is not necessarily better. Often, it's worse.
Flexibility exercise can take many forms, including methods that employ dynamic, active, isometric, and passive techniques. For our purposes here, I'll focus on passive stretching. Passive stretching is ideal for home training because it is highly effective, it is simple to perform, it doesn't require a partner, and it is generally regarded as the safest form of stretching. Performance involves assuming a stretched position and holding that position using only your weight, the support of another part of your body, or an external apparatus. When properly implemented, this allows for a gradual elongation of muscle tissue, permitting you to safely stretch your body to its utmost degree.
The key to passive stretching is to carry out movements in a slow, controlled fashion. When you stretch, ease your joints into a comfort zone and then maintain the position for the duration of the set. Go only to the point where you feel tension in the muscle—not to where you experience unbearable pain. Forcing a joint beyond the boundaries of its range of motion can overload muscles and connective tissue beyond their normal elasticity, heightening the potential for strain. The structures in muscles begin to break down when stretched beyond 1.5 times their normal resting length, while ligamental breakdown begins at a stretch of only 6 percent of resting length. Overstretching also initiates a phenomenon called the stretch reflex—an internal body mechanism that protects muscles from exceeding their lengthening capacity. The stretch reflex works by sending a neural impulse to the spinal cord that in turn signals the stretched muscle to contract—the opposite effect of what you're trying to accomplish when the goal is increased flexibility.
A majority of studies indicate that holding stretches for 30 seconds maximizes results; any less reduces gains in flexibility, while stretching for longer than 30 seconds offers no additional benefits. In most instances, one set is all that's required for optimal results. That's one of the beauties of stretching: You can realize improvements in flexibility by training just minutes a day.
To enhance results, you can isometrically contract the antagonist muscle before stretching the target muscle—a technique borrowed from a system of flexibility training called proprioceptive neuromuscular facilitation (PNF). Doing so brings about a phenomenon called reciprocal inhibition, where the muscle being stretched relaxes and thus is better able to elongate. For example, before performing a biceps stretch, you would actively tighten your triceps, hold the contraction for 10 to 15 seconds, and then proceed immediately to stretching the opposing muscle (in this case, the biceps). For the hamstring and glute stretch, you would tighten your quads before initiating the stretch. Give this technique a try and you'll see improvements in range of motion over what you could otherwise accomplish.
When to Stretch
One notion currently accepted as gospel in many fitness circles is that you should stretch before a workout in order to prevent training-related injuries. This tenet has been followed by everyone from recreational fitness enthusiasts to professional athletes for the better part of a century. Research, however, says otherwise. Stretching before exercise does little to reduce the incidence of injuries during the ensuing workout. The preventive benefits of enhanced flexibility on injury are cumulative. They come about from performing regimented stretching movements over time, not from an acute bout before a workout.
So when should you stretch? Generally speaking, timing really doesn't matter. As the Nike slogan says, just do it!
It's generally okay to stretch before a workout. Just make sure you warm up first. When soft-tissue structures are cold, they are at their most brittle and thus subject to breakage. A warm-up increases core temperature, thereby diminishing a joint's resistance to flow (viscosity). This is accomplished via the uptake of synovial fluid, which provides the joint with lubrication. Think of it as oiling a squeaky door hinge: The door opens much more easily after it's been lubricated. So 5 to 10 minutes of light cardiorespiratory activity or calisthenics will suffice in adequately warming up the tissues. The activity should work any muscle that will be stretched. So if you're planning to stretch the lower body, opt for activities such as walking, jogging, or cycling. Rowing is a good option before upper-body stretching. Jumping jacks, skipping rope, and squat thrusts work well when you're going to stretch the entire body.
Another option is to stretch at the end of a workout. Since core temperature is already elevated, your muscles and connective tissue are primed to stretch—there's no need to warm up. Postworkout stretching also can serve as a cool-down, gradually decreasing your heart and breathing rates and returning your body to a rested state. A cool-down is particularly important after aerobic training. It reduces the stress placed on the body and can help to prevent a sudden drop in blood pressure. Moreover, it aids in the redistribution of blood throughout the body. Otherwise, blood can pool in the muscles trained, potentially leading to cramping and stiffness.
You also can integrate flexibility training directly into your strength workouts by employing a technique that I refer to as selective muscular stretching. Selective muscular stretching involves stretching the muscle trained in between sets of lifting weights. The process is simple: As soon as you complete a set, immediately stretch the muscle being trained and hold it throughout the rest period. Not only is this an efficient way to enhance flexibility, but it can also help to restore blood flow to working muscles, thereby improving muscular recovery between sets.
Bottom line: Provided your muscles are warm, any time is a good time to stretch, whether it's before, during, or after a workout or on your days off from training. Moreover, you can stretch seven days a week, if desired. Since passive stretching doesn't significantly tax your neuromuscular system, it won't have any negative effects on recovery.