Running at a steady pace, an athlete typically burns 1 kcal per kilogram of body weight per kilometer, but accelerating requires much more energy.
At the Paris 2024 Olympics, athletes from 206 delegations will compete in over 300 events. So, which events burn the most calories? There are two ways to answer this, depending on the total energy expended throughout the event and the maximum energy consumed during a specific challenge.
Judo athlete Teddy Riner and track athlete Marie-Jose Perec lighting the torch in the Tuileries Garden, District 1, Paris, France, during the Olympic opening ceremony on July 26, 2024. (Photo: AFP)
Researchers often define the energy cost of an activity as the number of calories burned per kilogram of body weight per hour (kcal/kg/hour). Thus, if an activity expends 2 kcal/kg/hour, an average person weighing approximately 84 kg would burn 168 kcal if they exercised for one hour.
However, not everyone is the same. For the same activity, some people will use less energy, while those with a higher proportion of body fat typically burn more energy. On average, a resting adult consumes 1 kcal/kg/hour, and any activity requiring more than 6 kcal/kg/hour is classified as “vigorous – high intensity” according to the Physical Activity Guidelines for Americans.
This year at the Olympics, running events will burn the most calories per kilogram of body weight per hour. Accelerating demands much more energy compared to running at a steady pace. Therefore, events like the 100 meters—where athletes accelerate from 0 to 5 m/s in less than a second—will burn a significant amount of calories in a short time. Pietro di Prampero, a professor of physiology at the University of Udine, Italy, calculated that during the first 0.85 seconds of Usain Bolt’s world record 100 m sprint, he burned 91.2 kcal/kg/hour.
“In terms of metabolic power, the highest demanding event in running is definitely the 100 m. But in terms of total energy, if you run a marathon, the energy expenditure will be much higher,” di Prampero said.
Running at a steady pace, an athlete usually burns 1 kcal per kilogram of body weight. This figure does not depend on speed; therefore, running a marathon will burn 42 kcal/kg. The gold medalist in the men’s marathon at the Tokyo 2020 Olympics, Eliud Kipchoge from Kenya, weighed about 52 kg and burned 2,339 kcal when he crossed the finish line. His running time was 2 hours and 8 minutes, equivalent to about 21 kcal/kg/hour.
Runners at the Tokyo 2020 Olympics. Photo: Reuters
According to the Compendium of Physical Activities, a comprehensive review based on data from hundreds of studies estimating energy costs, activities such as biking at speeds exceeding 32 km/h burn 16.8 kcal/kg/hour. High-speed rowing burns 15.5 kcal/kg/hour. Martial arts consume 10.5 kcal/kg/hour, while trampoline jumping uses 10.3 kcal/kg/hour.
In swimming, energy demands vary depending on the stroke, the athlete’s skill, and the competition environment (pool or open water). “For professional swimmers, the stroke that requires the most energy is breaststroke, followed by butterfly, then backstroke. The most energy-efficient stroke is freestyle,” shared Tiago Barbosa, a sports science professor at the Polytechnic Institute of Bragança, Portugal.
According to research published in the International Journal of Sports Medicine by Barbosa, the energy cost of swimming breaststroke at a speed of 1.6 meters per second—slightly slower than Adam Peaty’s speed, the British gold medalist in the 100 m breaststroke at the 2020 Olympics—is approximately 30.4 kcal/kg/hour.
Events in open water may expend more energy due to the athlete’s exposure to waves, wind, and cooler temperatures. Barbosa noted that athletes save energy when swimming in a drafting position—swimming behind others to reduce drag.
However, both di Prampero and Barbosa emphasized that these calorie figures can vary significantly from person to person. “These are just estimates. I stated that the average Olympic runner burns about 1 kcal/kg for each km. But if you are an elite runner, you might expend 0.95, or with good shoes, it could be just 0.83. If the terrain is wet, energy costs will increase. At the Olympic level, a difference of just 0.01 can be the difference between winning and losing a gold medal,” di Prampero noted.
