For those to whom it needs to be said, check with your doctor before beginning any training program. Anybody who has a heart attack and starts out by trying to pin it on me, because you've let yourself go, will be cheerfully laughed out the door.
And if your chest or anything else hurts when you're exercising, stop doing that. Pain is sometimes weakness leaving the body. Usually that manifests as sweat, not agony. (If you get to doing BUD/S-level PT, we can talk.) Other times it's your body telling you you've screwed something up. No one else will be there to hold your hand, so you're going to have check yourself, and if something isn't working, get it looked at. You jack yourself up later in life, you aren't going to heal quick like you did when you were a teenager either. You can increase tempo and exertion over time a lot quicker than you can stop, heal, and start all over.
Anybody too crippled up to do anything here should be doubling down and using this time to get better at everything else. So if you're a paraplegic, you better be an awesome mechanic, or the tribe is going to throw you out to face Lord Humungus on your own.
Also, in a notional two-week training phase, you're barely going to be scratching the surface of training yourself and getting into shape. You'll be barely halfway into a toughening phase, and maybe not even that far.
That said, the goal here is to make this part of you. Practice becomes habit, and habit becomes lifestyle. But only if you start.
For a first session, do some light warmup exercises for 10-15 minutes. The fitness training manuals explain what military recruits learn as "The Daily Seven" from those who know them well. Go through the referenced FM, and pick out seven different exercises. The point is to slowly move all your muscles, and get your body warmed up, so that you don't pull anything. Like tendons, ligaments, etc.
Select exercises that vary the part stretched, arms, legs, upper body, back, neck, abdomen, etc. Don't do all leg exercises, or all arm exercises, or all simple stretches.
Whatever you pick, unless you're in shape already, start small. Do a minute or two of each exercise, at most. Call it 5 to 10 repetitions. Do the stretches s-l-o-w-l-y. You're trying to perform, not break yourself on Day One.
Once you've done them all, there are two fitness standards you should know about.
The Army PRT, and the Marine Corps PFT.
Quick and dirty, the Army does push-ups (max effort), sit-ups (in 2 minutes), and a timed two-mile run.
The Marines do pull-ups (max effort), abdominal crunches (in two minutes), and a timed three-mile run.
Relax, you won't be doing either one. Yet.
And I'm not going to start some silly inter-service flame war.
Start with the Army PRT model.
When you can, move to the Marine PFT model.
But for the first day, do max push-ups, one minute of sit-ups, and a timed quarter-mile jog.
Week Two, and each week afterwards, you're going to add one rep to each exercise in the Daily Seven, until you can get to 20.
Each week, add twenty seconds more to the sit-up period, until you're doing the sit-ups for the full two minutes.
Every third workout, you'll add 1/4 mile to your run distance, until you're doing the full two miles. That means it'll be 5 weeks, running three days a week, until you're up to 2 miles.
(1/4-1/4-1/2-1/2-3/4-3/4-1-1, and so on.)
At that point, you start doing the warm-ups more vigorously, and/or pick out some more challenging exercises for your Daily Seven. Jumping jacks and neck stretches are fun. But mountain climbers and flutter kicks build character.
You always try to max out on push-ups. Even beyond 100%.
Same for sit-ups. Go beyond the max score number in the same time limit.
And start pushing up the pace on your run time.
This is for every other day. Call it MWF.
Tuesdays you work on upper body alone.
Do the same warm-ups, at the same place you're at. If you have access to low parallel bars, use them. Two sandbags, or coffee cans filled with cement, on end, will allow you to do bicep lifts of your body sitting on the ground. Do push-ups and pull-ups. Rope or pole climbs.
Do weight lifts with individual arms, and both arms together, whether it's free weights, machines, bowflex, or paint buckets full of cement..
Your goal is to just work out your upper body: shoulders, biceps, and forearms.
Thursday, you work on lower body: abdomen and legs. Crunches, flutter kicks, mountain climbers.
If you can, do sit-ups where your body starts head down, your legs are on a table, and you use your back muscles to do reversed sit-ups.
Each time you do focused workouts, warm up well, start where you can, and gradually increase time spent and repetitions.
Saturdays, you work on cardio. Walk fast, jog, bicycle, swim, whatever. Do it easier than your MWF runs, but for longer periods of time.
Sundays are a day of recreational rest. Go to the park, the zoo, an amusement park, take an easy hike somewhere, play a sport. You're not working out, you're just not laying like a slug. Think of it as an all day stretch for some muscles that'll be tired.
You can score yourself here:
Army push-up standards.
Army Sit-up standards.
Army two-mile run standards.
Don't worry cupcakes, they have male and female columns, and they list the scores handicapped, all the way to the 62+ age bracket. (Feel free to compare yourself with 18-year-old studs, and up your game, once you're in the groove.)
The entire program is here:
If/when you transition to the Marine card:
Marine Corps PFT scoring.
That's the 18-y.o. stud standard. You can dig around the internet on your own for the older age brackets.
Military.com, (the link for the USMC scoring) also has additional links to things like circuit courses, interval training, and other military fitness and agility tests.
Start with the basics, until you've achieved mastery, then you can start varying your routine.
That will be hard enough, from a cold start.
Your goal is not to over-train or overuse your muscles and body, but to slowly and steadily build in progression until you reach and maintain a healthy and useful level of fitness. Nobody wants you broken, but you're no good to anybody, including yourself, if you can't move and manipulate your own body weight, and do useful work, in any number of tough times and situations.
You can figure out the days, but space them as I've indicated, and start slow.
If you miss a day, whether it's because you're a lazy fat bastard (like I sometimes am), or because work and life occasionally get in the way, get back on the horse the next day, and make it up.
There's a reason both WRSA and about every other post on John Mosby's Mountain guerrilla site keep hitting the same two letters: PT, PT, PT.
Excuses won't get it done, nobody ever drowned in sweat, and fit people are harder to kill.
And if you're feeling froggy, here's a motivational goal for you: