We are a commune of inquiring, skeptical, politically centrist, capitalist, anglophile, traditionalist New England Yankee humans, humanoids, and animals with many interests beyond and above politics. Each of us has had a high-school education (or GED), but all had ADD so didn't pay attention very well, especially the dogs. Each one of us does "try my best to be just like I am," and none of us enjoys working for others, including for Maggie, from whom we receive neither a nickel nor a dime. Freedom from nags, cranks, government, do-gooders, control-freaks and idiots is all that we ask for.
We generally recommend resistance (weights) for strength-building, but some people are just afraid of weights or associate them with body-builders. Wrong, but whatever.
However, there are some exertions which can be useful upper body fitness-builders without weights. Four calisthenics in particular: Pushups, pullups, planks, and Burpees.
These are far from comprehensive, but they cover lots of the basic muscle groups, and proper pushups stress core too. There is a reason these are basics of military basic training.
Another good thing about them is that they can be modified until you can do the real thing. For examples, you can do "girl" pushups (on knees) until you can do real ones. You can do assisted pullups (with bands) until you can do real ones. Everybody can do straight-arm or elbow planks, but duration is the challenge. Aim for several minutes. Shoulder-touch planks are a cool variation. Burpees (with the pushups and jumps) are a great upper-body and whole body calisthenic.
How many? That depends on you. Generally speaking, for a middle-aged (45-75) guy or gal who avoids weights, I'd aim for 25-50 pullups assisted or not, 100 pushups (modified or unmodified), 3 or 4 30-45-second planks, and 50 Burpees. Not all in a row, but on the same day.
(For general fitness without weights, this can (should) be coupled with a day of lower-body body-weight workout (eg lunges, squats, step-ups, box jumps, etc) plus a couple of days of cardio. That all is good enough for casual or club tennis fitness, or for a long day hill hike.)
When life gets back to normal, then we can return to our usual routines. Or maybe just stick with these sorts of things.
25-50 pullups??? Love your posts, however...back in the day, there was a TV show called 'American Gladiator', the usual tripe of athletes and an obstacle course. Evidently, to audition, there was a pull-up bar set up. Keep in mind, these were people who were Olympian trialists, arena football players and the like. BEFORE you could audition, you were told to do 22 pullups in 30 seconds. There was a 90% wash out rate. True or not, that is an impressive challenge.
I accepted a challenge from my nephews to do a "Murph" workout on Memorial Day (run a mile, then do 100 pull-ups, 200 push ups, 300 squats in some order, then run another mile). I've been training for it doing sets of 3 pull-ups, 9 squats, and 6 pushups; then resting 30 seconds between sets. Not worried about the running part. So far, so good, did 8 sets the other day and could have done more but trying to not get hurt. So, every other day add a few sets, and work up to sets based on 4 then 5 reps. Pretty good full body workout. If i can't make it for Mem Day, hopefully by July 4th.