i eat an average diet, not crap all the time but not overly healthy but i find i can ride all day everyday for at least a week without getting completely knackered. remember to warm down, i think thats how i get away with it. i usually have to ride a mile back from the station so that warms me down, and stretch when u get home. thats all I do and i rarely get too tired to ride and my muscles rarely ache. maybe have alook at your bike. the set up can cause bad posture resulting in aches. low stems and long bikes are bad.