I am always intrigued when I watch the start of the marathon during the summer Olympics. All the runners appear to be in top physical shape, excited to represent their countries and determined to win the gold medal.

However, it’s a whole different story when I watch them 15 or 20 miles later. They look exhausted from the hot sun that beats down on them or miserable because of rain that makes their trail slippery. Some have trouble breathing when the race takes them over a mountain, and others struggle to keep up with the fast pace.