I’d agree wholeheartedly with everything olivesmarch4th said (and strongly second the recommended sports bra). You might also consider investing in a cheap digital watch - if you’re anything like me, knowing when you can stop is important.
For my first 5K, I followed a training program that focused mostly on time (it’s hard to focus on distance at first). The nice thing about the program is that it’s so gradual, it really minimizes discomfort. And if you walk on the days you don’t run or do some other activity, your discomfort will be even less.
It had me starting out with 1 minute running, 1-2 minutes walking. Repeat 6 times (include 5 minutes before and after for warm up and cool down). I did that for about 4 runs, then graduated.
Next was 2 minutes running, 1-2 minutes walking. Again, repeate 6 times with 5 minutes on either side for warm up/cool down. Do it for 4 runs.
Another graduation: this time to 3 minutes running, 1-2 minutes walking. Repeat 5 times with 5 minutes on either side for warm up and cool down. Repeat 4 times.
Next level: 4 minutes running, 1-2 walking, 4 times.
Next: 5 minutes running, 1-2 walking 4 times.
Next: Jump to 8 minutes running, 1-2 minute walk, then 5 running, 1-2 minute walk.
Next: 10 minute run, 1-2 minute walk, 8 minute run, 1-2 minute walk.
Next 15 minute run, 1-2 minute walk, 8 minute run, 1-2 minute walk.
Next 15 minute run, 1-2 minute walk, 15 minute run 1-2 minute walk.
Next: 20 minute run, 1-2 minute walk, 5 minute run, 1-2 minute walk.
Next: 25 minute run, 1-2 minute walk, 5 minute run, 1-2 minute walk.
Next: 30 minute run. By this time, your graduation to a 5K will probably be adding 8-10 minutes on to your time (if that), depending upon your pace. I’m assuming a very slow pace (about a 12-minute mile), though you’re bound to be faster.
After that, I worked myself up to 3 marathons. Since I ran them, I’m kind of back to the beginner’s stage. Tonight I’ll be doing my warm up, 10-minute interval, 1-2 minute walk and 8-minute interval followed by the 1-2 minute walk and 5-minute cooldown.
A few things to keep in mind:
Your lungs will probably feel a bit constricted or almost like you’re stretching your lungs at the end of your runs. You’ll also be out of breath. This is normal. What’s not normal is being dizzy or completely unable to breathe. Same for heart rate - it should definitely be elevated, but your heart shouldn’t be racing.
You’ll probably experience some muscle soreness/stiffness and your shins will be sore. Your lower back may also be sore. Work through that. But if you feel any sharp, shooting pains or find it hard to move, walk or rest.
Getting into the habit of using good form is very important. When I started running, my shoulders tended to tense up and creep toward my ears. I also found myself slouching. Your shoulders should be back and when you’re on hills, you should be leaning forward slightly, but your back should be straight.
In general, when I run, I find it most comfortable to have my arms bent to where my thumbs would brush the waistband of my pants if they were to touch my body. My hands are most comfortable slightly closed like I’m holding an egg in each one. Also, it’s most comfortable for me to come down on the center of my foot - not the heel or ball - when I run. I also try not to waste energy with too much spring - I try to focus it all forward.
My first 5K was great. I ran it slower than I would have liked, but just completing it made me so happy. I was a little sore after, but no moreso than I would have been after a training run. The only other thing I’d recommend is that, if there are hills in the 5K, you should find some hills to run beforehand so you know what to expect.
Good luck! Let us know your progress.