A Step Down is a great exercise for runners, primarily aiding in hip stability and glute strength as well as working across the core and helping to improve balance.
To perform a Step Down start with your left foot on the edge of the step with your toes pointing forwards. Slowly bend your left knee bringing your right foot to the floor before rising back up again. After completing your repetitions on one leg, perform the same movement with your right foot on the edge of the step.
It is really important to remain engaged through the core and to ensure that as you bend your leg, your knee extends in the direction your toes are facing. It is best to take your time through the movement and not to rush any stage.