Evidence suggests that risk likely outweighs rewards for most athletes in runs totaling more than two hours in length. This information is particularly relevant for sub-ultra events including the marathon and half marathon distances.
When the goal of the run is to increase aerobic development, runs longer than two hours bring very few returns while increasing the risk of overuse injury. If you follow my training you may notice that I cap my daily aerobic targeted training at 90 minutes. While I do run longer on the weekend, I need to prepare my body for the damage and jarring impact of races lasting from 6-24 hours. This is not a coincidence, or due to time constraints, but rather a philosophy that is supported by science. Mitochondrial development tends to level off after 90 minutes of sustained aerobic activity. In fact, the majority of the physiological benefit or stimulus during a long run occurs between minutes 60-90. In terms of aerobic capacity, a 3 hour run doesn’t yield substantially more aerobic benefit than a run that is two hours in length. 90-120 minutes seems to be the optimal time for building mitochondrial and capillary density.
Increased Injury Risk
Late in long runs, especially longer than two hours, the typical runner’s form starts to break down. Muscles also begin to weaken and this leaves us susceptible to overuse injuries that can sideline us for days, weeks or even months.
What Can We do?
The truth is that most runners muscle and skeletal structure comprised of bones, ligaments muscles and tendons simply cannot keep up with their lungs. Following are some things that we can do to supplement and improve our bodies ability to handle the demands of training:
Cross train: Low impact aerobic cross training is a way to add in more aerobic stimulus while allowing our body to recover from the wear and tear of our weekly mileage.
Weight Train: Strength training, when executed and structured properly, can provide a multitude of benefits for runners including increased muscle and skeletal strength and resilience as well as improved body composition.