Muscle outlines from Body Muscles by Ivan Vulović, Apache 2.0 — regrouped and recoloured for Muscle Train.
Start on all fours, hands under shoulders, knees under hips, spine neutral, neck aligned. Brace your core and extend one leg straight back, knee locked, toes pointed down, hovering slightly off the ground. Drive your heel up, keeping the leg extended and using your glutes to lift until the leg is roughly in line with your torso. Squeeze the glutes hard at the top for 1-2 seconds. Lower slowly, controlling the descent, and repeat.
Maintain a locked knee and neutral spine throughout. Focus on pressing your heel into the floor, not swinging your leg. Keep hips square; avoid hip rotation. Prioritize core bracing before and during each rep. Master donkey kicks before progressing to the straight-leg variation.
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