The best way to improve your running fitness is to increase the amount of miles that you run. This is easier said than done. Not only will an increase in mileage leave you initially feeling tired, but it can lead to injuries. The secret to increasing mileage intelligently is to go up no more than 10% per week. For example, if you are running 20 miles one week, run no more than 22 miles the next week. Although this seems slow, it will make the jump much easier.
To provide even better protection against injuries from mileage increases, try to scale back mileage every so often. For example, go up 10% one week, up 10% the next week, down 5% the next week, then up 10% the week after. If you are currently running 40 miles per week, the next four weeks would be 40 miles, 44 miles, 48 miles, 46, 50 miles. It is hard to be patient when increasing mileage, but your body will thank you later.
