Muscle outlines from Body Muscles by Ivan Vulović, Apache 2.0 — regrouped and recoloured for Muscle Train.
Recline flat on your back with your legs fully extended, your arms stretched out, and your spine adjusted into a neutral alignment. Clamp your legs and glutes tightly together, then elevate your feet four to six inches off the floor while keeping your toes sharply pointed. Raise your shoulders and upper torso off the ground while reaching your arms straight overhead, aligning your biceps with your ears and keeping your neck neutral. Forcefully drive your entire lower back and hips down into the floor, holding this rigid shape static for your target duration.
Find a true neutral spine position while lying face up, adjusting your posture until you feel your entire lower back make solid contact with the floor. Keep your feet and legs pressed flush together with your arms fully extended behind your head, utilizing the long levers of your limbs to maximize abdominal recruitment. Limit the height of your feet to just four to six inches off the ground; lifting them any higher shifts the muscular focus away from your core and onto your hip flexors. Modify the movement if the full lever is too demanding by placing your arms flat on the floor to improve stability, or by raising your legs slightly higher to reduce leverage.
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