Although the amounts of time that individuals sleep can vary quite remarkably, with some sleeping as little as 4 hours a night, the average person sleeps between 7 and 8 hours a night. With harder training, the amount of time you need to sleep will likely increase.
Arthur Newton described the changes in sleeping patterns that occur with an increase in physical activity:
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Physical exercise needs more time for recuperation than mental work. While indulging in a heavy dose of this latter only, I used to find five hours’ sleep quite sufficient; but no sooner did I sheer off into rigorous training that I noticed a seven to eight hour stretch, or even more, was desirable . When it is a matter of super-intensive training, you may require as much as nine hours abed each night. (Newton, 1935, pp. 172-173)
Many runners don’t get enough sleep because they don’t budget for that time taken out of the day. If you are running 2 hours a day and sleeping an extra hour every night, then you need to budget 3 hours a day for training.