Muscle outlines from Body Muscles by Ivan Vulović, Apache 2.0 — regrouped and recoloured for Muscle Train.
Stand tall, arms overhead, feet hip-width apart. Brace your core, pull shoulders down and back. Drive one knee high, thigh parallel to the floor or higher, maintaining a slight bend in the standing leg. Simultaneously crunch arms down to meet the raised knee, squeezing your abs hard. Return to start and alternate knees rhythmically. Exhale on the crunch, inhale returning to the starting position. Beginners: 3 sets of 20 reps (10 per side).
Engage your abs, not your neck. Focus on bringing your ribcage towards your hip bone. Drive your knee upward explosively for cardio benefit. Maintain a tall posture between reps. Keep elbows wide to engage obliques.
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