I've been doing Couch to 5k and I just started on week 3. Week 3 kicked my butt!! For those not familiar with the program it's an interval training where they gradually add more running until at the end of nine weeks you are doing 30 minutes of running. Well, week 3 has me running for 3 minutes. I'm doing it on the treadmill because it's so cold outside (even though I started outside, I moved to the treadmill when it got down into the single digits). Anyway, I noticed that with 3 minutes of running, I was having to slow my pace on the treadmill just to make it through three minutes. My question is, should I go back and repeat week 2 at the faster pace, or try to stick with week 3 and just run at a slower pace? Which is more beneficial, running longer at a slower pace, or running faster for a shorter amount of time?
For C25K, you're better off slowing a little and doing the longer runs. This will benefit you more as you get further into the program, will be easier on your body, and it will make injury less likely. A common mistake of beginning runners is running too fast.