1. Aerobic Exercise
This type of exercise focuses on your heart and lungs, and the ability of these organs to pump oxygen and blood into your muscles. Try wearing a heart rate monitor, so you can keep a check on your heart rate. Aim to stay in your optimum aerobic level (55-60% of your maximum rate).
2. Anaerobic Exercise
This type of exercise focuses on short bursts of activity with the absence of oxygen present. This allows you to sustain a specific intensity level for a short period of time. This type of exercise is useful for strength, speed and power, preferably used when there is a change in terrain, such as hill running.
3. Hit The Weights
This type of exercise focuses on working against resistance to develop the strength and endurance of muscle groups. Hit the gym to strengthen your muscles, helping you run those longer miles.
4. Run, Rest, Repeat
This type of exercise is the ability to prolong the amount of time where a near maximal speed can be maintained over time. 400m interval training (running as fast as possible then resting, then doing it again) can help improve your speed endurance.