Ignore extreme views propagate by experts . Both get some sort of results, however, there are other ways. Remember the physiological facts. Endurance is best increased by work between 80 and 100 per cent of the VO 2 max. Never lose sight of pure speed.
Speed is rate of stride x length of stride.
The first is improved by running up and sprinting 30m, the run up is not less than 20 metres. The legs are moving at maximum speed, but you will not be travelling at maximum speed until the stride-length increases 30m further on. Increased stride length comes from increased leg strength. Hopping regularly is a great strengthener, especially up gradients. Eat regularly and correctly .