Over the last few months I have been deliberately keeping my bike in a low gear for parts of my ride. I do this in order to increase my effort and improve my endurance, and have found that I am now able to ride longer and feel a little bit less tired afterwards. Needless to say, my average speed tends to suck whenever I try this! Does anyone else do this, and am I risking any injury (haven't noticed any additional stress or pain after my rides)?