Okay, so after yesterday's post, you know why a good base is needed before beginning a marathon training program, but what does "good" mean? Base mileage will vary from runner to runner and whether you're a beginner or an experienced runner will play a factor too. But a good rule of thumb for a solid base is to be running 4-5 times a week with an average total weekly mileage of 25-35 miles.
It's fine to mix it up during your base-building phase with fartleks, tempo runs, hill work etc. But, mainly the mixing-it-up is to help keep it fresh and fun, not for training purposes. In other words, your goal during the base-building phase isn't to kill yourself in each workout. You're just building miles, letting your body get acclimated to the miles and building endurance.
Keep in mind that the average weekly miles of 25-35 for a good base is just that...an average. It's not what you'd necessarily begin with (especially if you're a novice). Your first week of base building mileage may only consist of 15 miles. Just as your marathon training plan has you ramp-it-up throughout your training, your base-building will also increase, not in intensity, however, but in volume.
A good rule of thumb is to keep your weekly mileage increase to no more than 10%. Ramping up the miles too soon can cause injury. Your first week of base building might include 4 days of 3- to 4-milers for a total of 15 miles. The second week, you may keep your "during the week" miles the same, but increase one of the runs by 10%, making that day's run your "long run." Eventually you'll work your way up to running three to four 4- to 8-milers during the week and a long run of 10 miles. Remember these (for the most part) are low intensity miles. Save the intense workouts for when your marathon training kicks in to prevent from peaking too soon.
How many months of base building should you have? Well, again, that will vary from runner to runner. For a first time marathon runner (who is also fairly new to running), 6 months is a good time span for base building. Then the based building will be followed by 4-5 months of training. For a more experienced runner, 5 months of base building is a good goal to shoot for. For the old pro, 4 months is a good goal to shoot for.
One of the biggest mistakes a runner can make in marathon running, is to think the training begins with the 16-20 training plan he/she has downloaded off the Internet. Nothing wrong with the plan, but I can almost guarantee, if you asked the creator of the plan, he/she would say that their plans assume you have a solid base before beginning.
Remember that base-building is your conditioning period. It's your preseason training time. You're prepping your body so that when you start your "real training" you won't put your body into shock.