Reasons we don't exercise
Am I too slow to run?
No, you are not too slow to start running. In fact, the aim of training runs is not to run as fast as you can every time. Most runs, even for experienced runners, are at easy pace, at which they can hold a conversation.
OK, an experienced runner can hold a conversation at a faster pace than a beginner, but the principle is the same. When you start to run, never run faster than it's possible for you to speak in complete sentences without panting, struggling to find your words, or losing your train of thought. If you're struggling, you're running too fast.
A mistake made by most new runners is to start off way too fast. They can't sustain the pace; it leaves them struggling and gasping for breath. What's more, running too fast is self-defeating because it makes you want to give up, makes you think you'll never be a runner.
Running should not be painful. It shouldn't cause you distress. The way to build the desire to keep running is to run comfortably. You want to feel good about yourself. Every step along the way is an achievement, a victory.
It doesn't matter if your pace is a fraction faster than walking. It doesn't matter if you mix walking with running. The aim in the first month is modest, but it builds for the future.
All you need to do is walk-run for a minimum of 30 minutes, three to four times a week with rest days in between. After that first month, you will notice how your fitness level has improved.
At any time you can comfortably increase your running compared to walking, do so. But the running must never be painful. When you start to get out of breath, ease off, walk again. As a novice, you don't even have to think about speed training. That comes much, much later.
I've not found any pace that is too slow
(Jeff Galloway, author and coach)
The slowest portions of my training runs are always the first 10 minutes, which I run at a slow jog (9 to10 mins/mile pace). That's my warm-up, to get my heart, lungs, legs up to pace without stressing them unduly. I run the last mile slowly; that's my 10-minute warm-down. And after my run, I stay on my feet by walking the dog for 20 minutes.
The best advice for a beginner is not to worry about speed. And don't compare yourself to how fast you ran as a high schooler or college kid.
No one is as fast as they would have been, could have been, in an ideal world in a great team with top coaches. If you need to do speed comparisons, look at your age group peers or at runners of similar experience and weight as yourself.