They're not asking you to divulge your medical history. They're asking you to show that you're capable of functioning at a basic level of physical activity without issues in a profession that requires a basic level of physical activity without issues.
If they said "non-smoker required" or "must weigh less than 200 pounds" then sure, there's an issue, that's discrimination. But passing a physical? Especially if you'll, as you say, need a CDL? There are no problems.