The Science Of The Long Run
Many new runners training for the marathon are averaging anywhere from 9 minutes to 12 minutes per mile on their long runs (3:45 to 5-hour finishing time). At a pace of 10 minutes per mile, a runner will take roughly 3-hours and 40-minutes to finish a 21-mile run. While there is no doubt that a 21-mile run (or longer) can be a great confidence booster, from a training and physiological standpoint, they don’t make too much sense. Here’s why:
Research has shown that your body doesn’t see a significant increase in aerobic development, specifically mitochondrial development, when running over 90 minutes. The majority of the physiological stimulus of a long run occurs between the 60 and 90 minute mark. This means that after running for 3 hours, aerobic benefits (capillary building, mitochondrial development) aren’t markedly better than when you run for only 2 hours. Therefore, a long run of over 3 hours isn’t building much more aerobic fitness than one lasting 2 hours.
Furthermore, running for longer than 3 hours significantly increases your chance of injury. Your form begins to break down, your major muscles become weak and susceptible to injury, and overuse injuries begin to take their toll. This risk is more prevalent for newer runners whose aerobic capabilities (because of cross-training and other activities) exceed their musculoskeletal readiness. Basically, their bodies aren’t ready to handle what their lungs can.
Not only are aerobic benefits diminished while injury risk rises, recovery time is significantly lengthened. The total amount of time on your feet during a 3-hour plus run adds considerable fatigue to the legs, which leads to a significant delay in recovery time. In the long-term, this means you can’t complete the more marathon specific workouts, which I believe, and research has shown, are a more important component to marathon success.