If you want to drop your 5K time [1] or prevent injuries like lower-back pain [2], it's imperative that you begin to focus on strengthening your core. The muscles that make up your core are the internal obliques, external obliques, transverse abdominis [3], and the rectus abdominis muscles. Not only do these muscles protect your internal organs, but they help support the muscles of your spine, helping you maintain an erect posture, and are activated every time you breathe, sneeze, have bowel movements, and pick up objects. Since our abdominal muscles play an integral role in pretty much everything we do, it's important that we take the time to strengthen them.

Doing a few mountain climbers here and there won't get you a strong and sculpted midsection. Instead, to strengthen your abs [4], begin to incorporate ab exercises into your workout routine at least three times a week. To get you started out on the right track, we've rounded up 15 of our favourite ab-strengthening exercises. Choose three to five exercises from the list ahead and incorporate them into your workouts.

Related:

A Trainer Explains Why You Should Always Start Your Workout With Abs [5]

Plank With Knee Tap

• Start resting on all fours.
• With your palms flat, raise up off your knees onto your toes. Keep your hands directly below your shoulders.
• Contract your abs to keep yourself up and prevent your bottom from sticking up. Remember to keep your belly button pulled in.
• With your head and spine in line, keep your back flat — don't let it curve. Picture your body as a long, straight board.
• With control, slowly tap your left knee to the ground without moving your hips. Lift your left knee back up, returning to the starting position. Repeat the same movement with the right leg. This completes one rep.

High Knees

• Hold your hands at waist level.
• Hop the right knee up toward your hands, then quickly switch legs and hop the left knee up.
• This counts as one rep.

Dead Bug

• Lie on your back with a neutral spine and your hips and knees at right angles with your palms pressed into your thighs just above your knees.
• Pull your abs to your spine, keeping your ribs and pelvis still as you lengthen your right arm and leg out until they are almost parallel to the floor. Keep your torso and spine completely stable as the arm and leg move.
• Return to the starting position, and repeat on the left side to complete one rep.

Standing Wood Chop With Med Ball

• Start with the feet a little wider than hip distance apart, keeping the knees slightly bent, and bring the medicine ball to your left shoulder.
• On an exhale, pull your abs to the spine and "chop" the ball down diagonally across your body toward your right knee. Imagine you're chopping some wood at this angle and the ball is your ax — the move is a bit percussive.
• Focus on the rotation initiating in your torso.
• Control the ball back up to the starting position. This completes one rep.
• Remember you are moving with force but control. Don't give in to the momentum of swinging the ball around.

High Plank

• Start resting on all fours.
• With your palms flat, raise up off your knees onto your toes. Keep your hands directly below your shoulders.
• Contract your abs to keep yourself up and prevent your bottom from sticking up. Remember to keep your belly button pulled in.
• With your head and spine in line, keep your back flat — don't let it curve. Picture your body as a long, straight board.

Birdog

• Get on all fours, with your knees under your hips and your hands under your shoulders. Remember to keep abs engaged and keep your back flat.
• Reach out with your right hand and extend your left leg out behind you.
• Round your back and head to connect your right elbow with your left leg under your body. This completes one rep.

Cable Crunch

• Attach a triceps rope handle to the pulley on the carriage of a cable station. Adjust the carriage so that it's near the top third of the machine. The exact position will vary based on your height.
• Next, select the amount of resistance you want — 22.5 pounds is a great starting point. As you begin to become more comfortable with the movement, feel free to increase the weight.
• Facing the pulley, come into a kneeling position approximately one and a half feet away from the machine.
• Grab the triceps rope handles and brace your core. You should feel a light stretch in your abs; if not, increase the weight. Make sure your weight is in your shins.
• Simultaneously pull both handles with bent arms and perform a crunch. Your elbows should be parallel to your thighs.
• With control, return to the starting position as you maintain tension on the pulley. That completes one repetition.

Circling Plank

• Begin in an elbow plank with your forearms resting on the top of a ball.
• Keeping your core strong and your body still, use your arms to roll the ball in small counterclockwise circles.

TRX Knee Tucks

• With the straps at mid-calf length, place your feet into each of the foot cradles.
• Lift your knees off the ground, coming into a plank position with your hands directly underneath your shoulders. Your back should be flat and your core should be engaged (there should be no arch or dip of the torso visible).
• Bring both knees in toward your elbows at the same time. Extend your legs, returning to your starting position. This completes one rep.

Side Elbow Plank

• Begin by lying on your side. Bring your right elbow directly under your right shoulder. Engage your core, press your right elbow into the floor, and rise into side elbow plank.
• Stagger your feet so your left foot is just in front your right or stack the heels.
• Reach your left arm up toward the ceiling, which will help you lift your waist.

Reverse Crunch

• Lying on your back, lift your legs in the air with your knees bent. Place your hands on the floor beside you.
• Without momentum, use your lower abs to slowly curl the hips off the floor and into your chest. Slowly lower them back to the starting position.
• This counts as one rep.

Elbow Plank

• Start on the floor, resting on your forearms and knees.
• Step your feet out one at a time, coming into a plank position.
• Contract your abs to prevent your booty from sticking up or sinking. Your spine should be parallel to the floor, with your abs pulling toward the ceiling.

TRX Pikes

• With the straps at mid-calf length, place your feet into each of the foot cradles.
• Lift your knees off the ground, coming into a plank position with your hands directly underneath your shoulders. Your back should be flat and your core should be engaged (there should be no arch or dip of the torso visible).
• Pretend there is a string attached to your tailbone as you lift your hips up toward the ceiling (as high as your mobility allows). Lower back down into your plank position. This completes one rep.

Forearm Plank Hip Dips

• From an elbow plank, slowly rotate the spine to lower your left hip to just above the floor (about one to two inches from the ground). Come back to elbow plank.
• Now lower the right hip toward the floor. This counts as one rep.

Mountain Climbers

• Start in a traditional plank — shoulders over hands and weight in your toes.
• With your core engaged, bring your right knee forward under your chest, with the toes just off the ground. Return to your basic plank. Switch legs, bringing the left knee forward.
• Keep switching legs and begin to pick up the pace until it feels a little like running in place in a plank position.