On a short run where you will be doing efforts a warm up is essential - you should probably just have started to work up a sweat at 5km I'd be spending almost as much time on the warm up as the run! On longer runs you can treat the start as a warm up.
On a short run where you will be doing efforts a warm up is essential - you should probably just have started to work up a sweat at 5km I'd be spending almost as much time on the warm up as the run! On longer runs you can treat the start as a warm up.