Plenty of soldiers' lives depend on other soldiers' 100m dash times in combat... yet the military is quite good at preventing illegal drug use... and the drugs that soldiers most want to take are drugs that would harm physical performance
Obviously there are minimum physical requirements to serve in the military, but once you're in you are not going to start saving more lives because you can run a little bit faster.
Modafinil, one of the common study drugs that med students are known to use, is used by quite a few militaries.