This is a very good exercise for runners as it improves leg strength making a runner less prone to injury.
Position yourself in a lunge wih your right leg back. Swing your right leg forward hopping onto your left foot and return back down into a lunge position. Make sure to keep your core engaged at all times, this helps you to keep your chest lifted and not fall forward. Also keep your knee in line with your toes. If this exercise is too challenging do the exercise without the hop. Do 2-3 sets 12-14 reps on each leg.