Want to test your lower body flexibility? Try sitting on the floor with your legs extended.

If you can’t do it comfortably, you may have tight hamstrings and calves (the muscles along the back of your legs).

“Other reasons include tightness in the lower back, tight hip flexors, weak glutes and weak deep core muscles,” says Eser Ozdag, a yoga teacher at MoreYoga.

While you might not regularly need to sit with your legs perfectly straight, maintaining lower body flexibility is still important for proper bodily alignment.

Tight hamstrings can pull your pelvis into a posterior tilt, rounding your back, while tight hip flexors can pull your pelvis into a forward tilt, causing your back to arch.

Either position can negatively impact your posture and put extra pressure on your spine.

Ozdag stresses that flexibility and strength are equally important—a lack of core strength could also inhibit your ability to sit upright when your legs are extended.

With that in mind, here are three stretches that will help your lower body flexibility and one move to build core strength, recommended by Ozdag.

Four stretches to help you sit up straight with legs extended

1. Supine hamstring stretch

Reps: 2-3 Hold: 30sec each side

• Lie on your back. Bend your left leg and keep your left foot on the floor.
• Place a yoga strap, towel or belt around the ball of your right foot.
• Extend that leg toward the ceiling, keeping a slightly bent knee if needed.
• Breathe slowly and stop if you experience pain.
• Hold for 30 seconds, then switch sides.

2. Standing hip-flexor stretch

Reps: 2-3 Hold: 30sec each side

• Stand in a split stance, with your left foot forward and right foot back.
• Hold a wall, chair or worktop for balance if needed.
• Tuck your tailbone and gently squeeze your right glute.
• Push your hips forward until you feel a stretch across the front of your right hip.
• Keep your chest up and avoid arching the lower back.
• Hold for 30 seconds, then switch sides.

3. Standing wall calf stretch

Reps: 2-3 Hold: 30sec each side

• Stand facing a wall, and place your hands on it at shoulder height.
• Step your right leg back, keeping your right foot flat and toes pointing forward.
• Bend your left knee, lean forward and gently push toward the wall.
• Keep your right heel down until you feel a stretch in the calf and keep your right leg straight to target the calf muscle.
• Hold for 30 seconds, then switch sides.

4. Dead bug

Sets: 2-3 Reps: 6-10 each side

• Lie on your back with your legs up, knees bent at 90° and calves parallel to the floor.
• Extend both arms toward the ceiling.
• Gently press your lower back to the floor and engage your core.
• Slowly lower your right arm and left leg toward the floor, but stop before your lower back arches or lifts away from the floor.
• Return to the starting position, then repeat on the other side.