Originally Posted by
burnthesheep
It depends. Head over and read up some topics on Slowtwitch.
I race bikes for fun, but brick a run sometimes for the extra aerobic.
Running I actually have a much larger cardiovascular ceiling than my legs and weekly mileage allows me to use.
I can hold 180s bpm on the bike for 20ish minutes. On a run I get to about 170 and legs won’t turn over any faster. Cardio wise I should be able to do a sub 20min 5k. Legs and run mileage, that’s a huge nope.
Running is super economical for time with aerobic work though. Anaerobic, either works. Maybe even edge to the bike for anaerobic since it is non impact and can trash the legs as long as the energy stores allow. Running anaerobic form breaks down and you have to stop.
180 bpm I hope ur young cause that's way to high for older athletes....I agree with what u say ….marathon runners have skinny legs cause most of the work is done by the heart and lungs....pro bike riders have big legs and scrawny ass upper bodies ...goes to show where their efforts lie