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Beginning (gram on the left) – Lying on your back with knees bent and both feet on the ground, push through heels and lift your hips to the ceiling before coming back down. Keep lifting up and down, squeezing glutes at the top.
Intermediate (mom in the middle) – Lying on your back with one knee bent and one foot on the ground, put your other leg up in the air. Push through the heel and lift hip to ceiling, squeezing glutes at the top of every rep.
Advanced (me on the right) – Place one foot up on a chair or bench, and point the other leg toward the ceiling. Push through the foot on the bench, lifting hips to the ceiling. Keep repeating while squeezing glutes at the top of every rep.