To be honest, whilst sprints are useful in that regard, I think their impact is easily overstated. Plus, it needs to be done in quite a particular, controlled manner. If it's any use, I've posted on this subject on pages 145, 146, 169, 177 and 205 of this thread.
Just to add to Stuuuu's knowledge and expertise. I have been reading an inspiring book called The Art of Resilience by Ross Edgley. He managed to swim around Great Britain (1780 miles). Anyway he had a chapter which was interesting called '80/20 Polarised Training' I've quoted a few segments which you might find interesting :
You basically spend 80% of your time training aerobically at a low intensity and slow pace, then spend 20% of your time training anaerobically at a high intensity and fast pace. Aerobic is defined as 'occurring in the presence of oxygen' which means your body uses oxygen to create the molecular energy of the muscles needed to power all movements withing the body. You swim, cycle or run at an intensity and pace that means your body can provide enough oxygen and energy to the working muscles for long duration's . The emphasis is on training: Technique and movement efficiency The heart, lungs and body's ability to use oxygen to produce energy.
Anaerobic energy on the other hand can be created without oxygen and instead breaks down carbohydrates from blood glucose or glucose stored in muscle to produce the molecular energy of the muscles needed to power all movements within the body. You swim, cycle or run at an intensity and pace that means your body cannot provide enough oxygen and energy to the working muscles for long duration's. The emphasis s on training: Pain tolerance and getting comfortable being uncomfortable . The muscles ability to produce energy without oxygen
How do you know which energy system your predominantly using (aerobic or anaerobic) One of the easiest ways (like previously said in this thread) is to see if you can run and talk comfortably at the same time.
-If you can speak in complete sentences your running at an aerobic pace, which is sustainable for a long time. This is the speed at which you cruise.
- If you cannot speak in complete sentences you're probably running at an anaerobic pace, which is not sustainable for a long time. This is at the speed at which you 'kill'.
The point where you cross over is known as your anaerobic threshold.
Good examples are
100M Sprints being 100% Anaerobic and Marathon being 100% Aerobic
800m Run and boxing can be 50% each
Football is about 40% Aerobic and 60% Anaerobic
3 mile run is classed as roughly 90% Aerobic and 10% Anaerobic