Fall is my favorite time of year for running. Slanting sunlight and crisp, dry winds bring back fond memories of high school cross country in New England.
Not every runner is quite so sentimental about autumn, but here's a fact: fall is the best time of year to attain maximum fitness and run your best races. Not only is fall weather ideal running weather, but the position of the season in relation to the rest of the calendar makes it the ideal period to achieve running goals.
More: 4 Reasons to Run This Fall
Is Your Base in Place?
The first step in the process of building peak running fitness is building a solid base of aerobic fitness. The key to effective base building is consistency. You need to get out and run on a consistent schedule with few interruptions so that you can gradually build your mileage, endurance, and durability.
When runners think of base building they typically think of winter, when they are returning to fitness after an "offseason" break. The winter is a season of base building for many runners, but it's not an ideal season for base building in many places because harsh weather makes consistent, progressive training a challenge. The fair weather of summer is more conducive to establishing a solid fitness foundation.
Summer is, of course, the sunniest season of the year, and that can help your fitness in another way. Exposure to sunlight triggers the production of vitamin D in the body. Vitamin D, in turn, increases the body's production of calcitriol, a steroid hormone that affects more than 500 different genes, some of which are relevant to athletic performance. A recent review in the journal Sports Medicine reported that low vitamin D levels may reduce aerobic capacity and muscle strength and increase susceptibility to stress fractures and upper respiratory tract infections in athletes.
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In the general population, vitamin D levels are lower in the winter, when the days are shorter and people spend more time indoors compared to the summer. Seasonal fluctuations in vitamin D levels are less extreme in outdoor athletes, but are still significant. Your vitamin D levels are never higher than after a full summer of outdoor training, and that's another reason fall is the best time of the year to do your best running.
Yet another feature of summer that makes it a great season for building a solid foundation of running fitness is heat. While heat reduces running performance, it actually enhances aerobic fitness development. This was shown in a 2010 study by researchers at the University of Oregon. Ten days of training in a hot environment improved cycling time trial performance in a cool climate. It appears that some of the physiological adaptations that enable athletes to train more comfortably in hot weather also enhance aerobic capacity generally.
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