But aren't we still more likely to have problems such as arthritis and knees that make cracking noises.
Only if you
under-nourish,
over-train,
train unsafely and ..well follow the rule you posted "
If it wasn't painfully difficult then you didn't do it right"
I am afraid I don't agree with that. While it is a very macho saying..it is not likely to be the safest practice!
Proper lifting can be joyfully easy. There is some pain...but that feels good!
I started training before I was 8. I have trained over 25 years. Powerlifting, bodybuilding, running, walking, hiking, arm wrestling...
The majority of my injuries came from non-sports related incidents...and even those are healed up.
The few lifting related injuries I have ever suffered resulted from stupid, ego-driven training. I healed all those up.
Over the years, there can be wear and tear...but at 40 you don't train the way you do at 20, and at 50 you train differently, and at 60, and 70...Some of my clients are in their 70s...they do fine.
If you take care not to strain and tear at your ligaments and tendons...then you won't have much of that popping.
Commonly, arthritis...is not caused from lifting. If you eat poorly and poison yourself regularly with poor food choices, if you are exposed to many environmental toxins and if you continue to expose yourself to things you are allergic too...then you can expect arthritis.
Train smart, eat smart..live well and enjoy it for a long time!