I am not a fan of traditional sit-ups or leg lowers (especially double leg lowers) as often people perform these loaded exercises incorrectly or with poor form, which can lead to pain and injury, especially in the lower back.
Instead I prefer to teach my clients how to plank. The plank can be a great exercise to build strength around the muscles of the abdomen. It also helps develop strength in the shoulders, arms, and glutes. The plank is a simple, safe and effective core exercise if done correctly.
If you can maintain a neutral lumbar spine (see picture below) and are not hanging into extension then you should be able to include a plank in your exercise program.
Lie face down in a pushup position. Keep your palms on the floor next to your shoulders and your feet flexed with the bottoms of your toes on the floor.
Take a deep breath and press up into a pushup. Your body should make a straight line from your heels to the top of your head.
Draw your navel toward your spine and tighten your buttocks. Look at the floor to keep your head in neutral position and breathe normally.
Hold for at least 10 seconds and lower yourself back to the floor and repeat. As you get stronger try some advanced plank exercises.
What to watch out for
Your arms should be directly under your shoulders, entire body in a straight line (from toes to head) and back is completely flat, neither arched or rounded. Holding a plank with your bum sitting higher than the rest of your body means the exercise is less effective. If you find yourself doing this then the exercise may be too difficult for you and you should stop.
Don’t just hold a plank
Studies have shown that holding a plank for shorter periods of time (around 10 seconds) and performed more frequently deliver better results. One study from the University of Waterloo in Ontario showed that the endurance of core muscles is much more important than their strength when it comes to their primary role: to provide stability for the lower back.
Athletic performance depends on being able to generate power through your arms and legs. That power is only possible if your torso and hips provide a solid, stable platform. While holding a plank and your abdominal muscles fixed in one spot for two minutes will strengthen your core, it doesn’t mean this strength will carry over when you are doing more complicated activities such as running, jumping and playing sport. You need to be strong in 3D, not just straining in the plank position for two minutes.
Once you can hold the plank for a minute, make the exercise more versatile by adding in advanced movements such as these.