The Secret Sauce to Building Your Aerobic Base

Long Runs

Long runs stimulate the synthesis and storage of more glycogen in your muscles to improve your endurance. During each week of aerobic base-building, make one run significantly longer than any of your other runs, especially when training for longer races. If you're over age 40, you may need more than one week between long runs to recover.

Your long run shouldn't make up more than a third of your weekly mileage. This rule can be broken if you plan on running only a few times per week. But you need to be careful since the main reason runners get injured is because they are not systematic with how they apply the training stress.

Never make your long run three to four times the length of any other run during the week. You must have enough mileage during the week to support the long run on the weekend. Marathon training groups around the U.S. commonly increase the length of the long run without proportionally increasing the weekly mileage. It's one major reason why so many of the runners who belong to those groups get injured.

For your long runs, run at a comfortable, conversational pace (about two minutes per mile slower than 5K race pace, or about 70 to 75 percent of maximum heart rate). Lengthen your long run by one mile each week for three or four weeks before backing off for a recovery week.

More: 7 Mistakes to Avoid on Your Long Runs

If you're a new runner, you may need to run the same distance at least two or three times before increasing the distance. If you run more than 40 miles per week, or if you run faster than an 8-minute mile pace, you can add two miles at a time to your long run.

Since your legs have no concept of distance, only of intensity and duration, the amount of time you spend on your feet is more important than the number of miles you cover. Since women rely less on glycogen and more on fat during submaximal exercise, female runners may need to run longer than males to severely lower muscle glycogen to stimulate its greater synthesis and storage.

If you want to be a better runner, follow these guidelines. If you train smart, you'll build a base strong enough to support a statue and may even run a PR this year.