Muscles are biological engines. They’re not perfect, but they’re amazingly efficient at moving mass over long distances. To understand how good they are, you need to look at the calculation of calorie consumption and fuel energy.
Think about the average person riding a regular road bike. At a cruising speed of 15 miles per hour (24 km/h), the body burns about 0.049 calories per pound of body weight every minute. For a rider who weighs 175 pounds (77 kg), that equates to 515 calories per hour. Divided by the distance traveled, that’s about 34 calories per mile.
Now look at the fuel. One gallon of gasoline contains about 31,000 calories of potential energy. If humans could metabolize liquid hydrocarbons like internal combustion engines, the math would be crazy.
A human could travel 912 miles on a gallon of gas.
That’s a startling figure for human-powered transportation. Compare that to a typical modern sedan that gets 30 miles per gallon. The bike wins by a landslide.
But this comparison requires context. The car weighs more than a ton. The bicycle weighs about 30 pounds. The cars are also moving significantly faster than 15 mph, which completely changes the drag profile. Still, the basic utility of the human engine is undeniable.
There is a warning. You can’t drink petrol. Your digestive system will reject it and the toxicity would kill you. However, fat is chemically similar to gasoline. Both are long chains of hydrogen and carbon. If you could switch your body’s energy source from glycogen to liquid fat, efficiency would remain high. For example, vegetable oil contains almost the same caloric density per gallon as gas.
Professional cyclists move in a different physical area. Tour de France riders often go 25 miles per hour. Air resistance is not linear; it grows exponentially in speed. At these speeds, calorie burning triples.
Riders burn about 100 calories per mile. During the 100-mile phase of the race, a competitor can burn 8,000 to 10,000 calories in one day. In this high-speed situation, the efficiency drops to about 300 miles per gallon. Even then, it’s better than most cars on the highway.
The price of this efficiency is input. To maintain this performance, the rider must consume large amounts of food. The body is a closed loop. If you put energy into it, you get distance. When you stop energizing, you stop moving.
Because of this efficiency, the bicycle remains the most practical device ever invented for personal transportation. It exploits the sweet spot of the biological engine. It brings human power to the lowest possible resistance.
Cars are big. They are ineffective at low speeds. They waste energy fighting their own weight. The bike doesn’t care about weight. It’s all about rolling resistance and aerodynamics.
The human body is not designed for speed. It is designed for durability. We are persistence hunters. We run until the prey collapses. The bike is just a tool that allows us to transfer this endurance to the pavement.
So when you see a cyclist coasting down a hill, remember: they are not just resting.
