Is there a limit to human endurance? Science says yes. Duke Today, June 5, 2019. From the Ironman to the Tour de France, some competitions test even the toughest endurance athletes. A study of energy expenditure during some of the world’s longest, most grueling sporting events suggests that no matter what the activity, everyone hits the same metabolic limit, likely due to constraints on the digestive tract’s ability to break down food. Picked up by The New York Times, NPR, The Guardian, The Scientist, New York Post, CNN, Jezebel, Daily Mail, Discover Magazine, Outside Magazine, Science Magazine, Cosmos, U.S. News & World Report, The Independent, Popular Science, ABC News, BBC News, Inverse, Men’s Health, Business Insider, Runner’s World, IFL Science, The Telegraph,Quartz, UPI, and New Scientist.