The Olympic Games comprise so many different disciplines that it’s pretty much impossible to compare them to one another, physically speaking, yet people continue to try. But when it comes to which sport is the most physically grueling, it’s nearly impossible to argue against the decathlon, which literally translates to being ten sports rolled into one.

Over the course of two days, athletes entered in the men’s Olympic decathlon (women compete in a separate, seven-event heptathlon) compete in a string of ancient Greece-reminiscent sports: Day 1 consists of a 100-meter race, long jump, shot put, high jump, and a 400-meter race; Day 2 entails a 110-meter hurdle race, discus throw, pole vault, javelin throw, and caps off with a 1500-meter race.

The most famous decathlete of our modern era is, of course, Caitlyn Jenner, who competed as Bruce Jenner in the 1976 Olympics and brought home a very decisive gold. Today, the best-known athlete competing in the Rio decathlon is Ashton Eaton, who arrived at the sport, as did many decathletes, rather haphazardly.

The training is grueling — and hard to recover from.

During extreme physical exertion, your muscles require more oxygen than they do when they’re at rest. This is why your breathing becomes more ragged when you work out — your lungs are trying to pump air faster, harder. But we can’t always breathe deeply enough to bring our muscles all the oxygen they need, and it’s at that point that our bodies switch over to an anaerobic process, entering a state of glycolysis, wherein our muscles produce a substance called lactic acid — otherwise known as that annoying cramp you get in the middle of a run — that temporarily helps us keep functioning.

That’s all well and good, but as soon as we stop moving, we have to reconcile with the accumulation of lactic acid in our muscles. People generally blame lactic acid buildup for making us sore after exercise, but we actually don’t totally know why we experience that kind of muscle pain. Scientists suspect it has a lot to do with temporary inflammation. The effect can be mitigated by cooling down, stretching, and even cupping.

But muscle recovery poses a unique problem for athletes competing in the decathlon because of the stop-start nature of the game. Plus, these Olympics are in Rio, which has a unique climate that’s hot and sticky in the winter. Exercising in the heat and humidity can exacerbate muscle soreness, which only makes Day 2 even more taxing.

Drinking fluids is one way to recover — some decathletes load up on electrolytes immediately after the decathlon and drink gallons of water between events to keep their system as hydrated as possible. Others try more space age-y techniques — Ashton Eaton announced last summer that he was partnering with Nike in his recovery process by putting on a hood that essentially cooled his head. As he said in a press release:

“After asking questions about current recovery techniques, the conversation prompted me to ask myself: Why does it feel good, after running, to pour a bottle of water over your head? I don’t know the physiological answer, but the fact that it does feel better makes me perform better. ”

And isn’t that all anyone would want from the best athlete in the world?

Photos via Getty Images / Ian Walton

Kastalia grew up in Littleton, Colorado, and has a journalism degree from the University of Southern California. She spent the past year and a half backpacking around the world and recently moved to New York. Her RTs = unwavering personal convictions.