how often to run a week to prepare for a marathon
3. Know that the ideal time you should have been running is about a year before you join a marathon. Be comfortable running a distance of about 3 and 6 miles (4.8 and 9.7 km), and training at least 3 days a week for about 15 miles (24 km) or more.4. Try running in shorter races first. 2  Starting with distances like 5k, 10k and a half-marathon. 3  This will be a good way to increase your distances and get used to running in the 'race' environment. 4  You should follow these steps for at least a month before you run or walk your marathon.