I have been riding local trails for about 5 months now. I ride 15-20 miles about 5 nights a week and probably average about 10-12 mph. I am in it for the cardio workout, strengthening and would like to lose some weight...generally I just want a decent workout. I build in a few 1/4 mile sprints and enjoy a nice downhill coast, but overall I take my time getting around. Meanwhile I am getting buzzed by younger and older bikers, rollerbladers and actually had a jogger past me up the other night. I am of a mind when the bikers are 'passing on the left' at seemingly 25 -30 mph that they are probably out for a short, couple of mile, quick cardio workout and have not just pedaled the 15 miles I did....am I wrong here? So I am wondering is it all proportionate ...easier, slower and longer equal harder, faster and shorter rides. Are the benefits about the same? Should I speed up? Am I taking the long road to conditioning afterall?