Think you’re not “old enough” to start worrying about your hips? Think again. Your hip flexors are a group of muscles in your abdominal cavity that allow you to lift your knees and bend at your waist. If you don’t stretch them often enough, these muscles can eventually start to cause knee and lower back pain as a result of overuse.

Tightness in your hip flexors is what causes pain like this. There are a few stretching exercises you can do to help loosen them up, though. Even if you don’t like stretching, it’s worth it. Loose hip flexors allow you to run, jump and bend with greater ease — all important movements for a ton of different strength and cardio workouts.

These muscles may be small. But taking care of them will keep you on target to reach your training goals without leaving you in too much post-workout pain.

SUPINE GRAVITY STRETCHES

On a bench, lie on your back and let your legs hang off the edge. Pull in one knee toward your chest as far as you can. Hold it with your hands as you relax the other knee while letting that leg hang down, foot toward the floor. Hold that position for 30 seconds before switching to the other leg and repeating the same process. Both legs count as one set; do two more.

LUNGES

If you’re already experiencing back and/or knee pain, skip this one for now.

Kneel down on one knee, stepping your foot forward as far as you can while keeping it at a right angle. Extend your back leg behind you. Try to get it as close to parallel to the floor as possible. Hold this position for 30 seconds, then switch sides and repeat. Use lunges as a cool-down stretch after a cardio workout to loosen your hip flexors and also stretch other muscles in your legs and lower back.

DOUBLE LEG CURLS

Lying facedown on your stomach, flex your feet. Bend your knees, bringing your heels toward your butt. Hold that position for 30 seconds; that’s one set. Take a 10-second breather, then do two more sets. This is also a great way to give your legs a light workout whole recovering from yesterday’s leg day.