MUSCLES ENGAGED Back (lower) The lower back is often not trained because it is not visible in the mirror. If you have weak lower back muscles, there is nothing to help pull back against the spine, putting you at risk of developing poor posture (hunched over). Weak lower back muscles can also lead to lower back pain. Glutes Gluteal Muscles (Glutes) are one of the strongest muscles in the body and are the connecting point between your legs and back muscles. Glutes are used in a variety of actions from moving the leg to extending and rotating the hip, as well as extending and rotating the trunk of the body. Exercise Instructions Step 1 Lie face down with your arms stretched out beside you and your palms face up. Step 2 Lift your legs, arms and chest off of the floor as high as you can and hold for a second. Step 3 Relax your body, return to the starting position and repeat.