Is it better fitness-wise to ride at the maximum gear? I just wanted to know if I will be doing more effort while riding at the maximum gear all the time, rather than changing gears constantly.

My commute is an hour long, but I want it to be tougher on the muscles, I've tried going at the maximum gear all the time but I'm not sure I'm doing more effort by it.

Could someone confirm?
No - Struggling away in the small rear cog/large front chainring combo is bad.

Fitness is an overall term that has many components, so:


If you want power you need to work on intervals, which is as fast as possible at full power for short burst times, then recovery time at a middling state.
If you want to train for endurance, being at the steady state for as long as possible, but working to nudge the steady state up to a consistently higher average.
If you want to get somewhere and not be too stinky, riding at 10-20% less than your steady state is good.  I (try to) do this on the way to work, but its not easy.  I leave the fast run for the scenic route home.


Simply pushing really hard on your gears means you're exerting a lot of force through your knees, and mine ache just thinking about it.  Instead you want to pick a gear that keeps you around 90 RPM is the common thinking, but personally I pedal faster.  Any lower than 60-70 is going to damage/hurt your knees faster and produce no gain in fitness.