It’s not just the exertion experienced during running that discourages many beginners from continuing. It’s also the soreness experienced afterward. So-called delayed-onset muscle soreness is caused by muscle damage associated with unaccustomed levels of exertion. It’s another Catch-22. Once you get accustomed to the exertion of running, you will experience less DOMS. But you must first experience DOMS to become resistant to it.
While DOMS is unavoidable for the beginning runner, you can minimize it by “inoculating” your muscles to the stress of running when you start your running program. The muscles become more resistant to the stress of running after the very first exposure to it. Therefore, in your first workout you want to apply just enough stress to trigger this effect and no more, because doing any more will only result in more soreness without resulting in any more resistance to future muscle damage.
I suggest you make your first run very short—only about 10 minutes. And instead of running for 10 minutes continuously, break it up. Run faster than you normally would for 15 to 30 seconds, then slow to a walk. When you’re ready, run for another 15 to 30 seconds, then walk again. Continue in this manner until you’ve put in 10 minutes and stop, even if you feel you could do more. Sure, you feel good now, but you will feel sore tomorrow—yet less sore than you would if you continued. And most important, you’ll feel less sore after subsequent runs thanks to this inoculation.