Whether it is grandma's voice still ringing in our ears, "Cross your legs!" or simply a matter of comfort, when knees drop to the floor in a push-up, those ankles love to cross. When I first start working with a student accustomed to this modification, I am quick to break this habit. Why? Because this position can lead to an unbalanced pelvis and an unbalanced pelvis makes core activation difficult, if not impossible.
What's the core have to do with push-ups? Everything! If you look at the push-up, you are effectively dropping your plank to the ground. In the same way your core must be braced to maintain a long, strong line in your spine in an elevated plank, you'd bettter bet it is going to need to work that much harder when your elbows bend and you come closer to the ground.
So how does the crossed ankle modification affect your ability to engage your core?
The hips consist of two pelvic bones and the triangular sacrum in between. If the hips are level and the hips and sacrum are aligned, the legs will be able to sit evenly into their sockets and the spine can be straight.
Now, the bones of the body are held together by tendons and muscles, which run from one bone to the next. These keep the bones in the right place so that every joint can move properly. Each muscle has a specific length and when they are all in their ideal range of length, everything is held in perfect alignment. However, adopt a slightly different position and your joints will move out of place.
Crossing your legs stretches the outer thigh of one leg longer and the inner thigh of the other leg shorter. When the posterior hip muscles shorten, it can lead to tightness and discomfort in the lower back and hips. As these muscles tighten, the lower back arches and belly slackens. The spine is no longer in alignment and the pelvis is tilting anteriorly with a slight pull to the right or left, depending on the cross of the legs. Now, with all this happening just try to brace your abdominals by pulling your ribs away from the ground on the descent and you will see just how difficult things have just become.
Refer to the image above. Notice the shape of the lumbar portion of the spine. It is curved, dipping down. The belly dips downward toward the floor. Now look at the shape of the same section of spine below.
By tacking the toes to the floor, the thigh bones sit properly in the hip socket, and we are now focusing on the alignment of the spine. With spine straight, we now have all the core strength required to eventually lift these puppies off the ground. And isn't that the point of the modifications?
All the same principles apply to all one-legged push-up variations. Rather than tuck one foot behind the other, lift that foot into the air and focus on keeping your hips square to the floor and level to one another. Afterall, the one-legged variations are there to challenge the muscles along your sides that help to stabilize your pelvis and spine. By tucking a foot, we would similarly be stretching one side longer than the other. Yes?
Have fun playing with this one and push on!
Disclaimer: Fit Club is not a medical doctor and the information contained herein should not be taken as medical advice. These are not intended to diagnose, treat, cure or prevent any health problem. Recommendations by Fit Club are not intended to replace the advice of a physician or health professional. Please consult your physician or a health professional before beginning any diet or exercise program.