Just started C25K - have completed first 2 runs of week 1. Am using a treadmill but was wondering how fast should I run/jog. I am a bit worried about the old knees. Currently walking at 5.7 kph and jogging at 9 kph. Is this fast enough? I weigh 17st 8lb.
How fast should I run?: Just started C25K - have... - Couch to 5K
Start at a speed at which you can hold a conversation, without any snatched breaths or gasping. It may seem slow but is adequate for your body to adapt.
As you get fitter you may be able to still hold a conversation at a slightly faster pace. There is no need to go any faster during C25k than that easy, conversational pace.
Try walking on the treadmill until you can go no faster - then start to "run" at that same pace - this should/could be your running pace when doing C25K. You should find this pace to be very easy to do - although if it does feel a bit physically awkward then speed it up just a little until you are comfortable. The aim of C25k is to finish all weekly days workouts and to do so easily.