To Stretch or Not to Stretch Before Working Out?

it is safe to skip flexibility moves before running or taking a fitness class?
by Martica Heaner Ph.D., M.A., M.Ed.

Q. I got to serveral exercise classes where we dont't before going into the workout. Should I be concerned?

A. As long as you are warming up before you start doing vigorous or intense physical activity—and that includes strength training as well as cardio—you can safely skip a pre-workout stretch. In fact, some research suggests that you may perform better if you don’t stretch before intense or dynamic exercise. Most people tend to respond better to flexibility exercises when muscles are thoroughly warmed up anyway, so to increase flexibility, stretching at the end of a workout makes the most sense.

If skipping your pre-exercise stretches seems like surprising advise , it's because stretching before exercising is almost a ritual in some fitness disciplines. Dancers typically start off by doing “isolations” (exercises that move a joint through its normal range of motion) and long-held, deep, static stretches. Many martial arts include deep stretches before dynamic high kicks and jumps. And starting in the ’80s, the typical aerobics class format began with a few minutes of easy movements followed by deep stretches of all the major muscles. Many people believe that they will suffer injuries if they don’t stretch first. So it’s not uncommon to see people in the gym stretch before they run on the treadmill or launch into a heavy-duty workout.

But just because this approach is status quo doesn't mean it's the best way to start off a workout. In fact, research has shown that stretching, especially slow, deep, still (or static) stretches can create a pre-workout relaxation state in muscle fibers that actually inhibits their ability to contract powerfully. And if you are moving quickly (running, jumping) or powerfully (climbing, sprinting or lifting heavy weights), the last thing you need is muscle fibers that are slow to contract.

In 2007, the journal Sports Medicine published academic reviews looking at the effects of stretching on strength performance and at the research on the role of warming up and/or stretching in the prevention of injuries to muscles. Both reviews concluded that warming up was essential.

Warming up involves easy movements that take joints through their natural range of motion. So walking for five or 10 minutes is a warm-up for running. Marching in place and moving the arms and/or legs gently in different directions (doing arm raises, knee lifts, etc.) can warm up the body to do most any kind of exercise. The point of a warm-up is to increase body temperature, increase the lubrication of the joints, increase the blood flow to muscles and prime the nerves to transmit signals to muscles. A warm-up literally prepares the body to work efficiently once the intensity starts to increase: Muscles contract more easily, joints bend more smoothly, and so on.

Stretching, on the other hand, is not universally recommended. The research on whether it helps or hinders a workout—or leads to injury or prevents it—is contradictory. This is partly because of different research designs that have used a wide variety of stretches (from slow and deep to fast, dynamic stretches to contract-relax muscle maneuvers) and protocols (stretching for 10 seconds versus 90 seconds, for example).

The review on stretching before lifting weights found that strength performance could be hampered by stretching first. Other research has found that it’s better not to relax muscles with long, deep stretches just before asking them to contract with great force or intensity.

On the other hand, the review on how stretching and warming up affects injuries concluded with a recommendation that a warm-up with stretching should be performed up to 15 minutes before exercise. The authors point out that muscles work effectively when they can easily move through a joint’s normal range of motion, and that poor flexibility has been associated with higher injury risks. It’s unclear whether people who are very flexible—such as those who dance or do yoga—should emphasize maintaining a high level of flexibility or try to become even more flexible.

More research on what kinds of stretching are beneficial, how much and on which bodies needs to be conducted.

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Martica Heaner, Ph.D., M.A., M.Ed., is a Manhattan-based exercise physiologist and nutritionist, and an award-winning fitness instructor and health writer. She has a Ph.D. in behavioral nutrition and physical activity from Columbia University, and is also a NASM-certified personal trainer. She has written hundreds of articles for publications such as Self , Health , Prevention , The New York Times and others. Martica is the author of eight books, including her latest, Cross-Training for Dummies. (Read her full bio.)