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What Happens When You Stretch? And What Happens When You Don’t?

How dynamic and static stretching can work in your yoga routine to keep you limber.

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For years we were told that we were rubber bands—that if we didn’t stretch we’d turn crusty and snap from disuse. Then we were told that tension was good and that if we were overstretched, we’d be akin to a loose and useless rubber band. And now you might be feeling more like a yo-yo than a rubber band. 

So what’s the actual deal with stretching? What does it do for runners? And when should it be utilized?  Well, that depends on what type of stretching you’re talking about. 

Static vs. Dynamic Stretching

In regards to the rubber band analogy, David Behm, professor in the School of Human Kinetics and Recreation at Memorial University of Newfoundland, describes stretching to be more of a Goldilocks scenario: “You want a tighter but not too tight muscle and tendon,” he says. Static and dynamic stretching serve different purposes in helping your body reach that homeostasis needed to keep running efficiently.  

Static stretching usually involves moving a joint as far as it will comfortably go and then holding it. A static hold can last 30 seconds or more. It’s a very effective way to increase range of motion, relax muscles, and prevent post-exercise stiffness and soreness. Hurdler stretches or kneeling hip flexor stretches are considered static. 

Dynamic stretches are controlled, active movements aimed at helping your muscles rehearse the type of movement they’ll be doing while running. This kind of stretching activates the muscle, causing it to contract and physically warm up. “It also warms up and prepares the nervous system by increasing its activity in anticipation of the activity,” says Behm. Walking lunges, leg swings, and heel to sky pulses are all examples of a dynamic stretch. 

But stretching isn’t just about your muscles and tendons. A study, published recently in the Journal of Physical Activity and Health, found that stretching can also lower blood pressure by physically stretching the blood vessels. The authors found that stretching was more effective in doing so than walking was, a common intervention prescribed for people with hypertension. 

When Should Runners Stretch?

When just fitting the run into your schedule is hard enough, you might be tempted to cut corners in your warm-up and cool-down routines. But here’s why you should consider keeping up stretching. 

Stretching Before a Run

Stretching as part of a warm-up seems to be where the most confusion comes in. It’s a common question: Should you stretch before running? 

Static stretching, when held in long durations, can actually cause you to tense up and get tighter, which is not what you want right before going for a run. “A static stretch would be great if we were about to go hold a static position for an hour. But when we’re running we’re about to go do repeated muscle firing for a set duration. We need to be getting our bodies ready for that physiological movement, not a 30 second static hold,” says Mackenzie Wartenberger, head coach of the University of Wisconsin’s women’s cross country team and assistant track and field coach.

Instead she recommends focusing on dynamic stretches as part of your warm-up routine. The idea is to push your range of motion. “It’s all about pushing right to the point where you can feel it — it should feel a little bit like you’re on the edge of that range of motion—and then immediately backing off,” she says. That process should be repeated three to five times, aiming to go two percent deeper on each repetition. “That contraction or extension depending on what movement you’re doing that’s rapid and repeated, warms your muscles up and it gets your muscles and tendons firing.”

Nell Rojas, a strength and running coach and pro runner herself, agrees that dynamic stretching should be incorporated into the mobility work in a warm-up. “It kind of tricks your muscles, neuromuscularly, to relax,” she says. “You’re not getting any lengthening in your muscles, but your body will be able to relax a little bit.” 

Behm’s research has showed that some static stretching in a warm-up is fine. Some coaches like to incorporate a static hip stretch into the warm-up, for example. “If static stretching is incorporated within a full warm-up, there are trivial effects on performance,” he says. “Static stretching can decrease muscle and tendon injuries, especially with explosive actions, but stretching does not decrease the incidence of all cause injuries.”

Here are the key muscles you’ll want to stretch in a warm-up:

  • Plantar flexors
  • Hip extensors
  • Hamstrings
  • Adductors
  • Quadriceps 

Stretching After A Run

We’ve all been there; racing home after a workout to get other to-do tasks crossed off our lists. But in reality, skipping a post-run stretch will do more harm to your body than good. “The science that’s out there now is that static stretching is fantastic for the end of your cool-down. It’s a great chance to kind of lengthen your muscles and fascia and tendon fibers and kind of restore some mobility,” says Wartenberger. 

Wartenberger’s athletes start cooling down with walking drills, moving in and out of dynamic stretches. “Everything is really short and gentle,” she says. Only after foam rolling and allowing their bodies to completely cool do they go into static stretching. “If you’re not really prepared for static stretching, it can really do more harm than good,” says Wartenberger. Foam rolling first can relax the muscles and increase range of motion, which help reduce the risk of injury when going into a static stretch. 

This kind of stretching opens up your range of motion and increases flexibility; not stretching drastically reduces mobility in the joints and muscles, which increases your risk for injury—especially for runners, who constantly place stress on the muscles.

“Reduced flexibility in the muscle and joint leads to a change in biomechanics or normal function and contributes to increased tension at the tendon. For example, someone with tight quadriceps is more likely to develop patellar tendonitis because the tight muscle pulls on the tendon attachment at the patella, creating increased tension, inflammation, and pain,” says Anna Munoz, a former athletic trainer and current product specialist at DJO, a medical device manufacturer that develops orthopedic and mobility solutions.

Just five minutes after a workout is needed in order to stretch out the quadriceps and surrounding muscles to prevent patellar tendonitis.

Many runners also have tight hip flexors and hamstrings, explains Munoz. Forgetting to stretch these muscle groups can lead to knee pain too. “A patient will be prescribed exercises to both strengthen and lengthen the quadriceps, hip flexors, and hamstrings.” These muscles continuously pull on the patella. If they are tight, it will pull and cause more pain. Keep your muscles loose and limber with a good stretch to help prevent pain.

Here are the key muscles you’ll want to stretch in a cool-down:

  • Quadriceps
  • Hamstrings
  • IT band
  • Calves
  • Piriformis
  • Psoas
  • Glutes
  • Hip flexors/groin

The more you incorporate stretching into your routine, the more you’ll understand what does and doesn’t work for you. Try these runner-approved stretches to get you started.