In reply to petestack:
> (In reply to Alan.T)
> [...]
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> Depends on the miles and what you do with them, so you might just find yourself turning into a longer, slower runner (like me)!
You need to follow the regime that Arthur Lydiard set for his athletes, the long slow runs are followed by a periodisation up to an important race.
"Lydiard's ground-breaking impact on distance running was recognised by Runner's World, which hailed him as All time best running coach but to this day his unrivalled contribution to coaching middle and long distance athletes remains controversial.
A significant reason for Lydiard's ambiguous status in distance running, despite his unmatched achievements, may be found in the blunt and forthright nature of the man. He constantly clashed with unimaginative and officious athletics administrators in his native New Zealand and in the countries that called upon his strong personality and coaching expertise to establish national athletics programmes.
Another major reason for the failure of the athletics community to fully acknowledge Lydiard's achievement is that the training system he devised as a self-coached athlete in the 1950s is counter-intuitive. The fundamental premise of Lydiard's system is that to optimise one's performance even in middle distance events, such as the 800 metres and 1500 metres, one must train as if preparing for the marathon. This seems to fly in the face of common sense, given the high anaerobic and speed components of the these events. Lydiard's experience, now confirmed by exercise physiologists, was that marathon conditioning provided an athlete with the required endurance to sustain greater levels of speed over middle and long distance races than opponents whose training had not included an endurance base.
The marathon-conditioning phase of Lydiard's system is known as base training, as it creates the foundation for all subsequent training. Lydiard's emphasis on an endurance base for his athletes, combined with his introduction of periodisation in the training of distance runners, were the decisive elements in the world-beating success of the athletes he coached or influenced.
Periodisation comprises emphasising different aspects of training in successive phases as an athlete approaches an intended target race. After the base training phase, Lydiard advocated 4 weeks of strength work. This included hill running and springing, followed by a maximum of 4 weeks of anaerobic training (Lydiard found through physiological testing that 4 weeks was the maximum amount of anaerobic development needed—any more caused negative effects such a decrease in aerobic enzymes and increased mental stress, often referred to as burnout, due to lowered blood pH). Followed by a co-ordination phase of 6 weeks in which anaerobic work and volume taper off and the athlete races each week, learning from each race to fine-tune him- or herself for the target race. For Lydiard's greatest athletes the target race was invariably an Olympic final."
More on Arthur here
http://en.wikipedia.org/wiki/Arthur_Lydiard