This classic core exercise for the back body is especially good for strengthening and conditioning glutes and lower back with a minimum of risk. Lie on your back on the floor, then push heels and shoulders into the ground and lift your glutes. Your body should be in a straight line from shoulders to knees. Neck and head should be relaxed, with the spine supported by the muscles of the upper back. You can hold this position for a duration or slowly lift yourself up and down for repetitions.