Top definition
1-A running workout involving running multiple short sprints. It develops quick twitch muscles, and improves sprinting speed. Really damn painful. Commonly run to improve times in distances from 50 to 400 meters. Long and middle distance runners also participate in speed intervals, although the effects are less noticeable.

2-The length of time between fixes of a methamphetamine user.
1-We did like 400 speed intervals for track. I can't fucking stand up my hamstrings are so busted.

2-Will has such a short speed interval. He's always high. Let's go to KFC
by Exoskeleton October 23, 2009
Get the mug
Get a Speed Interval mug for your friend Riley.