Today is Patriots’ Day in Massachusetts, also known as Marathon Monday. The Boston Marathon is the oldest annual marathon in the world, with this year marking the 112th running of the 26.2 mile race.

Spectators line Beacon St, near mile 24 of the Boston Marathon.

Marathon running has come a long way since the largely mythical run of Pheidippides, a Greek messenger, who ran from Marathon to Athens to inform of the Greek victory over Persia in the Battle of Marathon. The thing is that Pheidippides died on the spot, right after delivering his message of victory. Science and training have filled the gap since then and significantly decreased the time it takes runners to complete the course. The runners’ equipment, such as the shoes and clothing, has obviously evolved past the leather sandals and togas favored in the times of the Greeks, but science has also affected nutrition and water intake, likely the two biggest factors that keep today’s runners fast and healthy.

The human body can only store approximately 2,000 kcal of glycogen, the simple carbohydrate that is easily broken down for energy. That energy translates into about 20 miles of non-stop running, not enough to complete the grueling 26 mile course. Once the ready glycogen supply is depleted, runners can “hit the wall,” or run out of energy and feel a wave of fatigue. Adequate training can combat the effects of glycogen depletion. Some runners choose to consume glycogen gels, specially formulated with sugars, salts, and caffeine to boost the athlete’s energy and help them complete the run.

Gel packs are commonly composed of specific ratios of simple and complex carbohydrates – 20% simple carbohydrate, such as fructose, and 80% complex carbohydrate, such as maltodextrin. This ratio has been shown to maintain a stable level of blood sugar for approximately 45 minutes after consumption. Tables and charts dictate the frequency with which the gels can be safely and effectively consumed in the course of the race, depending on how quickly the athlete runs. The level of water consumption is critical in aiding the spread and digestion of the gel. Too much water and you risk hyponatremia, a condition in which excessive water intake leads to a drop in plasma salt levels, leading to seizures, vomiting, and even death.

Water station for the runners.

Marathon runners have come a long way since the days of Pheidippides. The sport is now safer than ever, though certainly not easier. Every year when I watch the runners streak by, I am amazed and awed by their power and determination. It’s an unbelievably moving event and is a large part of the reason why I love living in Boston. It’s almost enough to make me start running… a mile or two.