Originally Posted by
sizzam
Am I doing myself a disservice by riding the mountain gearing?
No.
Should I step it up to the road bike and build strength on that?
Except for sprinting cycling isn't limited by strength. Burning legs come from your body's limited ability to process lactic acid, not low strength.
I'm thinking back to when I played little league baseball and my dad would tell me not to throw a tennis ball because it would ruin my arm. Am I ruining my legs?
No. Cycling training programs include a base phase where you spend a lot of time on rides with low to moderate intensity.