great for people just starting out who want to add a bit of speed into their runs, or as a way of mixing things up.
the premise is simple; run at an easy or steady pace and every now and then throw in a burst of speed. typically these bursts will last around 30 seconds, but it really depends on the runner. an example would be to run easy and then upon reaching a lamppost pick up the pace until the next lamppost is reached.
these short bursts get the heart rate up a little, but then soon lower it back down with a longer period of easy running. as such, there 