I noted in my last blog post that a lot of work on this past Tour de France remains to be done. I leave interested readers with a few tidbits in this space that have come from recent calculations.
Ever wonder how many Calories elite cyclists burn on a Tour de France stage? I can show you a great estimate. I adjusted my model's power outputs so that my model would "predict" the time that exactly matched all 21 stage-winning times. Energy burn in the body is a complex phenomenon, but a reasonable estimate is to assume a 20% efficiency in the body's conversion of consumed energy into useful output for cycling. Some muscle groups are more efficient; other muscle groups are less efficient. Check out the graph below.
Click on the graph so you can see it better. I plot an estimate of each stage winner's Calorie burn. You can see which stages are flat, medium mountain, mountain, and individual time trial, plus I include the distance for each stage to add some context. It's not uncommon to burn 6000 Calories on single stage! That's why cyclists need to eat while biking.
The combined total energy burn for the winners of the 21 stages came to 120,649 Calories, or an average of 5745 Calories per stage. To put that number in perspective, consider the following, tasty, but not-so-healthy food:
According to the McDonald's website, a Big Mac contains 550 Calories. That means that the average energy burn on a single Tour de France stage is over 10 Big Macs! Do NOT try to prepare for a Tour de France stage by consuming 10 Big Macs prior to the stage's start.
Figuring out weight loss with the number of Calories burned isn't trivial because fats, carbohydrates, fiber, and proteins (among others) have different energy densities. But, again, keeping things simple, one quasi-decent rule of thumb is that 3500 Calories have to be burned to get rid of a pound of fat (or consume 3500 Calories to gain a pound of fat). A Tour de France cyclist can burn nearly two pounds of fat per stage. Using the figure above for the sum of the winners' energy burn, a total of about 34.5 pounds of fat could be burned during the three-week race. Those guys have to eat while biking!
Though we predict a stage-winner's time, and we never go after a particular cyclist's time, it's interesting to see how the general classification winner's time compares to the sum of stage-winning times. Check out the table below.
You can see the time that Tadej Pogačar won the general classification with. The actual sum of stage-winning times is obviously smaller than the winner's time. The sum of my model's predictions is also shown. We were only about 6.5 minutes faster than the actual sum. Though the error looks great, a lot of individual errors were canceled. In other words, some of our stages were too fast, whereas other stages saw our predication come in too slow. But my model does a good job predicting the sum of stage-winning times, if ever anyone is interested in that number. Tadej Pogačar was only a bit more than three-quarters of an hour slower than the sum of stage-winning times. To put that into perspective, note that 146 riders finished the 2020 Tour de France. The last rider came in over 6 hours behind Pogačar! A time of about 45 minutes slower than Pogačar's time sits between the riders that finished in 15th and 16th places. In other words, even though he won just three stages, which is great, Tadej Pogačar competed extremely well against the winners of all the stages. He had one helluva great Tour de France!
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