Feeling stiff? Achy? Can’t move quite like you used to?

You’ve likely got one — or more — tight muscles to blame. And while the reasons why any one muscle can wind up tight, shortened and sore are plentiful, the biggest, most common culprit is sitting … typically while on a computer or other gadget.

“When you sit, you keep your hip flexors in a constantly shortened, yet under-load position,” explains Canada-based kinesiologist and medical exercise specialist Dean Somerset. After all, your hip flexors not only draw your knees up to your chest, they stabilize your spine and keep it in place. And as if tight hip flexors weren’t bad enough, all of their constant tension draws the top of the pelvis forward, pulling your hamstrings tight and keeping you from being able to touch your toes.

[See: The 10 Most Underrated Exercises, According to Top Trainers.]

Meanwhile, chances are that when you’re sitting, you’re also hunched over a keyboard, tablet or phone. “Ideal alignment is with the head directly over the spine, Somerset explains. “When your head moves forward, your upper [trapezius] muscles have to work extremely hard to keep your head from basically falling off your shoulders.” The result: They become incredibly short and fatigued.

“If your muscles have tightened up, blood has been squeezed out of them and they are not operating at 100 percent capacity,” says certified personal trainer Kelly Collins, co-founder of SISSFiT, designed to help women lead healthier, fitter lives. “Therefore, loosening your muscles will not only relieve stress and reduce your risk of injury, but improve your overall sports performance and the results you get from those workouts.”

Stretch This Way

Easing tight muscles requires more than a good bend and hold. That’s because muscle tightness occurs due to more than just physiological factors (aka: a muscle being contracted super tightly).

Tightness also occurs when your body’s neuromuscular control gets a bit overprotective. Your body is equipped with an array of neurons and protective tissues that have to fire (or not fire) in a certain way for any given muscle to stretch to its full physiological capacity, Somerset explains. So, to fully stretch a muscle, you first have to tell your neuromuscular system, “Don’t worry. It’s OK to stretch this far.”

[See: 7 Reasons No One Likes You At the Gym.]

Exercise physiologists commonly use a rehabilitation technique called “proprioceptive neuromuscular facilitation,” or PNF, to do this. While there are various ways to conduct PNF stretching, most experts believe the most effective version for combatting excessive tightness, increasing muscle length and improving range of motion is the hold-relax with agonist contraction method. It’s a mouthful, but it’s easy enough to perform at home with some help from a friend or family member.

Here, we explain how to perform the stretch with the commonly tight hamstrings. But remember that you can apply this same sort of stretch to any tight muscle.

Hold-Relax With Agonist Contraction

Perform two to four bouts of this stretch per day, either immediately following exercise or at the end of the day.

Step 1. Lie on your back on the floor, one leg extended straight toward the ceiling. Have a partner hold your lifted leg firmly, with one hand on your heel and the other on your knee.

Step 2. Have your partner press on your leg to move it toward your chest until you feel a mild stretch in your hamstring. Have your partner hold this stretch for 10 seconds. Make sure to relax into the stretch.

Step 3. With your partner still holding your leg firmly in the same stretched position, contract your hamstring to push against his or her hands and “fight” the stretch for six seconds. With both of you working in opposite directions, your leg should not move.

Step 4. Relax again into the stretch, this time using your quads to help “pull” your leg even closer to your chest and deepen the stretch. Hold for 30 seconds. You should be able to stretch the hamstring farther than you could during Step 2.

[See: 7 Exercises That Trainers Wouldn’t Be Caught Dead Doing.]

Beyond Stretching

Adding these strategies to your routine can help you get more out of every stretch.

1. Improve your core strength. Oftentimes, short, tight muscles are due to nothing more than a weak core, explains certified strength and conditioning specialist Holly Perkins, author of “Lift to Get Lean.” That’s because the core’s in charge of stabilizing your spine and pelvis. So, when your core is weak and, thus, your spine and pelvis get out of proper alignment, you’re bound to tighten some muscles. Perkins recommends improving core strength through core stability exercises such as planks and “dead bugs.”

2. Perform regular resistance training. Research from the University of North Dakota shows that strength training improves flexibility just as well as — and in some cases better than — passive stretching does. For the greatest benefits, authors say you need to make sure that you move through your full range of motion during every rep and set. So, instead of “pulsing” your hips in a glute bridge, raise them up as high as you can and then lower them all the way to the floor.

3. Pair your stretching with foam rolling. Before diving into your favorite stretches, spend some time with a foam roller. One comprehensive review published in the International Journal of Sports Physical Therapy concluded that foam rolling is effective at promoting short-term increases in range of motion, most notably when performed in conjunction with stretching. Collins recommends that, no matter your activity level, you spend at least 10 minutes three times per week stretching and foam rolling.

More from U.S. News

Please Don’t Fall for These Fitness Trends, Experts Beg

7 Pieces of Workout Gear to Ditch or Replace

Summer Workouts: How to Handle the Heat

4 Simple Ways to Ease Tight Muscles originally appeared on usnews.com