Top end speed/ hill sprints.

The theory behind incorporating "Hill Sprints." into the training is on strengthening your legs and challenging your heart and lungs to work harder. By strengthening your legs via hill sprints, you make it easier in theory for a greater top end speed while keeping your heart rate down. This makes it easier to keep your heart rate within the pre set limits on your heart rate monitor. Your heart and lungs will have to get stronger and become more efficient which they will do in time.