Exercise dogma long has extolled the value of stretching. But what kind of stretching is best? That’s a topic that’s been debated for decades.

From the 1960s to the late 1990s, fitness professionals firmly believed that slow — known as static — stretching was better. Later, however, research suggested that so-called dynamic stretching, which looks more like exercise, was the answer.

Today, many experts think a combination of both is the best approach.

To understand the controversy, it’s important to know what happens at the muscles’ cellular level during static stretching.

“Our muscles are made of thousands of muscle spindles — like hairs in a ponytail — that give the muscle cell the ability to stretch and contract by sliding past each other in a coordinated fashion,” said Michael Jonesco, an assistant clinical professor of sports medicine and internal medicine at Ohio State University’s Wexner Medical Center. “Static stretching pulls on the cell to the max, and can cause some stretch injury that takes time to recover, and can therefore cause a temporary drop in performance.”

But at the same time, regular static stretching conveys a number of benefits. It increases range of motion in the joints, enhances flexibility, improves circulation and reduces risk of injury, among other things.

“I like to think of stretching as a way to optimize the range of motion about your joints,” said Edward Laskowski, a physical medicine and rehabilitation specialist at the Mayo Clinic. “The more motion you have, the better the muscles can work.”

But he’s not dismissing dynamic stretching. It puts the muscles in motion repetitively and “is essentially preparing your muscle in a gradually progressive fashion to do the job you want it to do,” he said. “For example, you may want to do a front kick in martial arts or in dance. So you would start with some slow and gentle kicks, gradually increasing speed and intensity until you are performing the kicks you normally would.”

A comprehensive review of the scientific literature over the past 15 years tried to put the controversy to rest. After considering hundreds of studies, researchers concluded that a mixed warmup — static stretching along with dynamic stretching — was the optimal approach.

“Brief periods of static stretching, often followed by dynamic periods of warmup, is a great means to prepare for competition,” Jonesco said.

Laskowski agreed. “A combination of stretches is likely best,” he said. “Static stretching to ensure equal flexibility side-to-side and to optimize range of motion about the joint, and dynamic stretching as a preparation for a sport or activity, especially one requiring explosive movements.”

An unpublished preliminary study suggests that static stretching helps the elderly and those with impaired mobility because it increases blood flow to the muscles. “You are never too old to gain a benefit,” Laskowski said. “Our connective tissue tightens as we get older, so stretching is beneficial as we age.”

For optimal benefit, he suggested holding a stretch for at least 30 seconds. Don’t bounce, which can cause “micro trauma” to the muscle, he added. Symmetry also is important to prevent muscle imbalance, which can lead to injury, he said.

Jonesco agreed. “Be sure to do both sides, right and left,” he said. “I also recommend antagonistic muscle pairing, as well — front to back, for example, quad and hamstring.”