Joint pain is a whole other thing, though. Usually joint pain means that you're doing some sort of exercise incorrectly, or that you're using too much weight or intensity for your current level of physical fitness. Or you have a previous injury that can't fully heal and there are some exercises that you just shouldn't be doing, but you do them anyway.

But I think the author is talking about less pain in a different way. For example, I threw out my lower back 25 years ago in college, and it's never been the same since. But doing core exercises and strengthening the muscles around that area means much less chance of pain doing regular day-to-day activities.

I’m a triathlete of 4 years now - love to be sore but have never been injured & unable to train.

There are three things you must do:

1. good technique: lift with the right muscles, run at the right cadence & target heart rate.

2. listen to your body when it needs less or more load.

3. treat recovery as equally important as exercise itself. Exercise’s mirror.

That said, instead of actual complaints, your friends might be social signaling! Bringing it up to bond over the joy of exercise. Humans do that subconsciously, and there is a ton of joy to bond over!

Once you get in a routine of doing it at least twice a week you won’t get that soreness anymore. People who start working out, then miss a month, then start back experience it all the time. Consistency is key.

https://www.researchsquare.com/article/rs-5753318/v1 (pre-print) seems to provide a strong argument for strength training being beneficial. My search was not thorough so likely more studies out there.

My personal thoughts and anecdote, assuming you're not talking about the kind of "bro I got in a killer workout yesterday, my biceps are still sore" Delayed Onset Muscle Soreness humblebragging:

I have a controlled autoimmune disorder like arthritis that causes me some joint pain. But it basically goes away if I do regular strength training. If you do strength training or any sport long enough you'll eventually hurt yourself. Usually that's just a pulled muscle because you woke up on the wrong side of the bed and it goes away after a few days. These micro-injuries actually seem to happen to me a lot, probably because of my condition I'm just prone to this stuff. But I prefer it to the pains of inactivity.

Even for people without arthritis, you have a question to answer: which would you rather suffer from? The pains from not working, out like having a weak core and bad posture and the discomfort of being unable to climb a few sets of stairs? Or the pains from working out, like pulling a back muscle because you didn't warm up or some shin or knee pain from too much running?

The answer is obvious to me. You're going to get hurt either way. I'll go with the path that makes me feel better, live longer, look hotter, and is a rewarding challenge.

You should feel the exercise and specific muscles afterwards, sometimes even a day after (like hamstrings and thighs from squats, those don't get much workout during normal life), but after initial beginner phase the continuous long term goal is to get enough workout that muscles are not sore, just notch below. Properly sore muscle needs few days rest, a well used one can be again fully loaded in 48h easily.

And overall definitely less pain or more like 0 pain, ie back from weak core is pretty typical. Another one are knees, but to train knees around some already-damaged tissues is more tricky, but definitely worth it.

After starting weightlifting (on top of some sports like ski touring, climbing, hiking etc) I can handle much more, heavier and longer. Need to move your/friend stuff to another apartment? All day carrying with them feels like mild stretch, compared to them complaining for back pain for another 3 days.

I’m often complaining about soreness here, a lightly pulled there, a big joint that needs to be left alone for a few days. It’s annoying but also even kinda satisfying, and I know how to avoid serious injury.

I’m not complaining about lower back pain because my fitness activity has rid me of it. That pain would have stopped me from being able to move easily, work on my cabin, play with children, and would have eventually made me overweight and chronically ill.

The tradeoff is really a no-brainer in my case, and I don’t think my case is so unique.

If you do nothing for 20 years and then go for a 20km walk - you'll be in pain. But it's the 20 years that caused it, not the 20 km.

Sore muscles -> good workout.

But I think running is higher impact on the body that a lot of of other exercise. You're putting your full body weight on a small area several times a second for many minutes every day.