A lot of people only have a GP (doctor) and those GPs often discourage bicycling. Years ago I had problems with fatigue whilst riding up a hill here in town that I normally didn't even gear down on. My GP told me to stop riding the bicycle for a long time. A sports medicine doctor diagnosed the problem and I was able to correct it whilst still being able to ride the bicycle.

Not all doctors are created equal.

As George Carlin once said: "Somewhere there's a doctor, who graduated at the very bottom of his class, practicing medicine.

(laughter from the audience)

"The really scary thing is that there's a roomful of people waiting to see him".

Cheers