Exercise by club swinging in the 19th century

An hour a week of heavy (for the lifter’s current capability) deadlifting or squatting in three 20 minute sessions will definitely get serious results with good programming. One will see increases in muscle mass, bone density, and improved cardiovascular health from just that. Granted it would be beneficial to do more, but point is even an hour a week can be an effective training stimulus.

Keep in mind that exercise seems to have a different and separate effect from eg cutting down the number of hours spend sitting around each week.

I think an hour a week is sufficient.

For me the guideline for general population should be basically intermediate strength standards like the prescriptions by NASA, which are hilariously low but calibrated to maximize muscle retention, mission capability and most significantly reduce injury. Mission capability for gen pop is just to have enough muscle so you don't shatter your hips during a bad fall or injure yourself on rudimentary tasks (carrying your kids) that lead to expensive long term care.

The NASA standard was something like bodyweight squats for 6-10s that most people should be able to cultivate quickly and maintain with minimal effort. The difference in space is they have to exercise for 2 hours a day to maintain muscle mass, but on earth you can crack out BW or 1.5xBW squats/deadlift and insipidly low bench/ohp for homework 3x10s in 30m sessions twice a week to maintain. The bar is exceedingly low. Of course that varies depending on genetics, but it's one of those situations where pareto principle comes into play.

Cardio vascular health is different, but mostly it's a balance between NEAT, actual cardio and maintaining a healthy BMI, while strength training maintains an useful amount of muscle mass. Barbell Medicine podcast has a lot of good info on strength training + rehabilitation. It's geared towards the powerlifting crowd, but along your point, one of the broader prescriptions is that frequently movement and exercise is better at healing than pills or other medical interventions, but movement is very infrequently prescribed.

"Where is the dividing line between building your body up and wearing it out?"

From personal experience: roughly aged 50 (give or take, probably give.) That's without farting around with big weights.

600lbs is about 270 kilos. There is no reason for your body to need to deal with moving weights like that unless you are in a competition or trying to save a life. Hence it is not built for loads of that magnitude on a regular basis. Running with an 80-100 lb pack/load on your back and holding a 20 lb lump is a reasonable load to put on a very fit body, aged up to say, around 40. Your local Army, Marines, etc will know better than me what to encourage here. Try this lot: https://www.paradata.org.uk/unit/infantry-training-centre-ca... for example.

I'll just suggest that for most people, messing with weights like that are simply daft. We are not fork lift trucks. In the rest of the world, 25 kilos is considered a normal one man lift.

Humans as a species are designed for endurance, not huge loads.

The reason I compare it to construction is that at some point, pursing lifting to a high degrees involves putting in the amount of repetitions that amounts to a job with high statistical injury rate. If you follow bodybuilding and powerlifting closely, the amount of people who wash out due to injury is staggeringly high, to the point where an injury free career is anomalous and often credited to great genetics (tendon strength) than smart training. In fact the majority of the injuries happens on routine warm up reps, and because these people are enthusiasts and treat lifting almost like a job, they don't manage healing properly and will often continue training while injured leading to long term detriment. The particularly bone headed people will lift until they break their body and washout, but even smart lifters (who plan stress and fatigue sensibly) will eventually get injured past a certain level. This is like working in construction, people accrue damage over time, small injuries compound or big injuries take them out. The amount of work required in these occupation/hobbies are not calibrated for "health".

[1] https://www.strongerbyscience.com/powerlifting-injuries-resu... >The overall number of people injured may surprise you. Of the 160 people who finished the study (either sustained an injury or made it through the whole year uninjured), almost ¾ of them sustained an injury. That seems to conflict with the finding that injury rates in powerlifting are only ~3-5 per 1000 hours of training. Assuming someone trains for five hours per week, that would mean you’d expect a lifter to get injured about once every four years, on average (or, stated another way, you’d expect about ¼ of lifters to get injured per year). However, keep in mind that we used a pretty broad definition of “injury” , compared to the more conservative definition used in other research. In another study on powerlifters using a pretty liberal definition of “injury,” 70% were injured at the single point in time when data was collected, so I’d say the overall injury rate seen in our study is to be expected. Taken collectively, the data suggest that powerlifters sustain minor injuries pretty frequently, but more serious injuries are pretty rare; comparable to triathlon training, but less common than long distance running or most team sports.

I wasn't arguing against deadlifting. I was arguing that the correct strength training recommendation for general population is a baseline that optimizes for useful amount of strength, protective amount of muscle and minimal amount of injury. And for me that level is shockingly low, i.e the NASA low BW multiplier prescription. Everything beyond that is basically for enthusiasts with elevated injury risk over a long enough time scale. There's nothing wrong with enjoying lifting as a hobby so long as it's understood that training for strength past a certain point is the opposite of exercising for health. See my Barbell Medicine endorsement above, I mentioned that strength training, i.e. deadlifts is a good rehabilitation tool that's often under-prescribed as medical incentives doesn't align with cheap gym memberships. Though ironically for me, deadlifts is the best rehab for deadlift injuries.

My best gym pull is 660 @ 185. My observations in powerlifting is that injuries in squats/deadlifts doesn't start to mount until "enthusiasts" start trying grinding past their intermediate plateau because they're motivated but also reckless. This typically occurs between 2x-2.5x BW. Sometimes it's hot headed kids on stupid programs who thinks they're invincible, and sometimes it's just diligent trainees who misgrooves one rep on a 90% topset after 5 years of training. It's not a question about poor form but high statistical likelihood when regularly dealing with heavy weights over many reps for many years. The heavier one lifts relative to whatever individual genetics allow, the more catastrophic a misgroved rep becomes. It's simple leverages. Force/stress from 405lb vs 225lb on a misgrooved moment-arm doesn't scale proportionally to load. 1/3 of lifters about above novice skill experience lower back injury of some sort (see stronger by science link I posted) which makes heavy training not something I would endorse for people just looking for to exercise for health.

>we shouldn't be walking around either for fear of tripping.

My endorsement is the minimum amount strength train necessary so a trip doesn't shatter your hips (particularly older populations), which is very low but sufficient bar.

Sure, but they might expect more work than you'd want to do.

Yeah. Cross-fit is a franchise system, and they don't have much centralized QC. So it's very hit and miss.

You know, it just occurred to me that, despite growing up on a farm, I can remember very few used tractor tires; one was a raised bed and the other a sandbox.

Probably has something to do with a lack of vehicle inspections for farm equipment.

Put it on your tractor. Then simply remove it when you need to exercise.