Remember when a 2:05 marathon was a big deal? These days, you can run 2:04 and not even make the podium, as has happened the last two years at the Dubai Marathon. As the running community wonders when the first sub-2:00 marathon will be run, science is exploring how, exactly, the body will get the job done.
Multiple factors are at play, of course, including body type, biomechanics, training, and environment. A new paper in the International Journal of Sports Physiology and Performance discusses the crucial role nutrition is playing in pushing the marathon toward the two-hour mark.
In the paper, Trent Stellingwerff, Ph.D., a physiologist at the Canadian Sports Institute-Pacific in Vancouver (who happens to be married to a 1500-meter Olympian Hilary Stellingwerff) reviews multiple fueling and hydration studies from the last several years and anecdotal reports looking for key issues influencing performance.
Among the most intriguing is the emerging practice of training on low carbs. Doing some workouts when the muscles are glygocen-depleted (i.e., hungry for pasta) is believed to help improve the body’s ability to use fat as fuel. The more the body relies on fat early in a run, the more carbs will be available during the late miles of the marathon when runners need them most to maintain pace.
The data, Stellingwerff notes, suggest that periodically decreasing carb intake before workouts may enhance endurance. He cites pioneering research from 2005 that found that when untrained male athletes did half their training in a depleted state—they ran twice a day; the second training bout on little refueling—their endurance improved. (It’s important to clarify that glycogen-depleted training and low-carb diets are not the same; athletes are not restricting total calories, but experimenting with the timing of meals and workouts to best enhance performance—something that only experienced recreation runners should consider.)
An anecdotal report shows that East African runners—the vast majority of the world’s record-setting performances have been set by Kenyan and Ethiopian athletes—practice glycogen-depletion training. It’s unclear, though, if the approach is intentional or, if due to high training frequency, they just don’t have time to eat.
A case study conducted on three elite marathoners who gradually increased the frequency, duration and qualify of low-carb workouts resulted in two runners improving their marathon time, from 2:16 to 2:11 and 2:15 to 2:12; the third clocked a 2:16 debut.
Whether the best training-on-low-carb approach is overnight fasting or limiting refueling before a second run remains to be determined, Stellingwerff notes.
Not surprisingly, race-day fuel was another key topic in the paper. Research shows that finding the right amount of fuel intake during competition greatly affects performance.
“It is important to note,” writes Stellingwerff, “that even minor GI distress is associated with negative endurance performance outcomes.” He adds that the body can be trained to better process fluids and carbs, but that it’s up to each athlete to find his “sweet spot.”