Speed
 

i can run/slow jog forever, but i can't build up speed. what kind of exercises can i do to speed myself up?

first of all, try doing weight lifting for your legs. squats and lunges are good.

try interval training. when you run, instead of doing a long, slow run, do your warm-up, then jog for a few minutes, sprint 30 seconds, jog again another few minutes, sprint another 30, wash rinse repeat.

also, time your long runs. say you do 3 miles in 35 minutes. work on speeding it up slowly. maybe try interval training 2 days a week, long runs 2 days a week, and then the other 2 do shorter runs like maybe a mile, working on doing them faster each time.