Running and learning are similar things
If you aren't in the habit of doing either regularly, the sensation you get when you get around to it can easily be mistaken for pain. Most people don't /want/ to learn, they want to know. Likewise, most people don't /want/ to run, they want stamina, or weight loss or whatever. The actual act of learning is painful for people, as is the physical act of running long distances.
I submit however that pain is not what you're really feeling. I say that because one never truly acclimatizes to pain. Here's an experiment that requires a hammer and a clock. Got them? Ok, take note of the current hour on the clock, and then, placing your left hand on a table, and taking the hammer in your right, smash the pinky of you left hand with the hammer. Now repeat this action every day at the same time for a week.
That's pain. And what you'll find is that you won't get used to it. The all too obvious point of this ramble is that not only do you get used to running, you get to like doing it for the sake of doing it. It starts to be fun, if you give it a chance. Likewise for learning, but it seems to me at least that a taste for running comes more easily to most people than a taste for learning. Indeed most people spend more than a decade in school without acquiring a taste for learning. Running you can get a taste for in about 4 weeks.
I have, I think, a fairly unique outlook on running. In my youth I was an athlete and a Marine. I benched 314, ran marathons, and climbed mountains. I had personal trainers, pro-skills coaches, and drill instructors, I was highly motivated and truly dedicated. At the age of 19, I was 6'4" and 219lbs, I exercised at least 5 hours daily (not counting partying and sex!), and there wasn't much I felt I couldn't accomplish physically.
Then I got what is known in USMC parlance as "Fat, Happy, and Stupid". I have various excuses for this (not counting partying and sex), the end of college, the end of active duty, marriage, a long commute to work, take your pick. By my 26th Birthday I was 6'4" and 310lbs. If you check the BMI charts, I believe that combination is referred to as "Morbidly Obese".
Around 28 I got fed up with myself and started dieting and running again. I even have a running team. I'm no svelt 19 year old, but at least the BMI charts no longer actively mock me. So if you're thinking about running, or just starting out, I may have some useful advice for you. I've run the spectrum, no pun intended, and have a healthy respect for what it takes to build some momentum.
Oh, and by the way. I'm just some guy on the internet, so you should probably not be listening to me. Running is like, dangerous and stuff, so don't do it. And if you do, don't freeking sue me.