Day no. 21 – Barbell Hip Thrusts. Lie down on the ground on your back with your knees bent and feet flat on the floor. Make sure your neck is in a relaxed position and your lower back is pressed into the floor. Keep your arms at your sides with your fingers pointing towards your lower body. Now, lift your hips towards the ceiling as high as you can without raising your feet or shoulders off the floor. Try to get a straight line from the shoulders to the knees. Squeeze your butt cheeks together when your thrust your hips up. Lower your hips down and make about 20 reps.