It's a runner thing.

If you’ve never run before, I recommend doing a Couch-to-5k training plan, like the one from coolrunning.com.

If you have been running several miles a day, a few times per week, just keep doing what you’re doing, and add in some hill repeats, longer runs than you’re used to, and intervals (fartleks are good). 

If you used to run but have been slacking off for a few months, start with what you’re comfortable with and increase slowly, using the 10% rule  (don’t increase your mileage by more than 10% per week) to not get injured.

Also it’s a good idea to add in strength exercises for your core, legs, and upper body, like plank, side plank, leg lift, burpees, mountain climbers, lunge jumps, clamshells, wall squat, pushups, tricep dips, etc. Good luck!

thanks! :)

r u calling me fat or something