Originally Posted by JerrySTL

You shouldn't be mashing the higher gears to build muscle. What you should be doing as spinning the pedals at somewhere between 75-95 rpm. It's much better on your knees and will build up the correct fast twitch muscles that are best for cycling. Once you start spinning, instead of mashing, the pedals, your average speed will go up and your knees will thank you.

You paid a lot of money for all those gears. Use them properly and shift often.