The solution to the Olympic Games challenge [1] is adenosine 5′-triphosphate (ATP; Formula 1). To be precise, the NMR spectra presented in the Olympic Games challenge [1] were measured from the more stable ATP disodium salt (C10H14N5Na2O13P3), but the spectra measured in D2O are indistinguishable. At the 2012 Olympic Games in London, Usain Bolt, the reigning Olympic champion in three Olympic events, ran the 100 m and 200 m with nearly the same average speed of 10.38 and 10.35 m/s. In contrast, Stephen Kiprotich—the 2012 gold medalist in the men’s marathon—required 7,681 s for the 42,195 m. So, his average speed was “only” 5.49 m/s. Since endurance athletes are no less motivated than short-distance runners, the following question arises: Why must a marathon runner reduce his or her speed and run at almost half the speed of sprinters? The answer lies in the solution of this challenge, or more exactly, in the rate of synthesis of ATP in human muscle cells. The coenzyme ATP is the only direct fuel for muscle cells, regardless of whether an athlete is trained as a sprinter or as a marathon runner. The concentration of this direct fuel for muscles inside the cell is typically 1–10 mmol/L. Surprisingly, the total amount of ATP in working muscles is constant. Even extremely hard work does not lower the ATP concentration by more than about 20%. Several differing energy sources are used by working muscles to maintain the ATP level. During the short sprint period, the major driving forces are stored high-energy phosphates and anaerobic breakdown of glucose. Consequently, the 100 m sprinter can perform almost without breathing just by using the energy stored as ATP and creatine phosphate in the active N N