This exercise works into your hips, glutes, and hamstrings, with a particular focus on the hip extensors which are vital for producing a powerful stride and maintaining knee stability when running.
Set up with your back against a block or step which you will be able to press your shoulders into. Have the barbell across your lower tummy - you may wish to add a pad to the bar for greater comfort. From here, push your back into the block behind you and thrust your hips into the air. At the top position you should have your shins at a 90 degree angle with the floor.
Your head should stay in line with your spine throughout, this means it will be looking slightly more ahead as you come down and will be looking at the ceiling in the top position. The bar does not need to come all the way back down to the floor between repetitions.