My experience is a little different than what Steve Maxwell describes, although I do agree with alot of what he says.
Regarding muscle building at 60 I'm almost there yet find it no problem to build or maintain muscle mass, probably from having a past base of muscle built starting 42 years earlier. I know I can't match what I've done in the past but nonetheless I'm happy with the results of even a small amount of hypertrophy based training as my body seems to respond quickly.
The area where I feel the effects of age is more in the speed/strength realm. I can still move fluidly and have the 'pop' and power throwing MA technique but I'd be fooling myself to think it hasn't diminished to some degree. I can still jump fairly well but the landings are a little tougher so I don't do too much of it.
I know many people promote the idea of 'less is more' when it comes to training but again I believe it varies greatly from person to person. Using myself as an example I've always tended toward alot of training, that's what my body and mind are used to. These days I'm doing VWC 3-4 times/wk along with 2-3 strength sessions with MA training as well. VWC is very demanding so I'll take days off as needed. My markers for a day off are:
- not enough sleep
- not enough food
- sore or stiff joints
- flat muscles
- a general feeling of malaise
- dehydrated
Since adopting VWC I'm in a flux state and figuring out training vs. rest days. Most people seeing my age and schedule would probably say I'm over training, but it's been my MO for so long it's what I'm accustomed to doing.
As you train over many years you learn to read signals your body sends out and make adjustments accordingly. This is what I use to gauge training. Another development in the last couple of years is injury prevention strategy. It used to be if I felt a tweak while doing a set I'd note it but continue without issue, nowadays I've learned to stop immediately after one as it's a very small window of warning. When I don't listen often times I'll get something more serious on the very next rep.
Right now I'm in the process of simplification and consolidation with training as I search for efficiency.
For me, I feel the joints complain sometimes, and I definitely need to warm up a bit to get going. This is stuff I've read about for years, so no surprise I'm feeling it as well.
The one aspect of aging I feel the most is my ability to cram calories - its just not there like it used to be, and that really is what limits any mass gains I might shoot for (although training at home and not having barbells and a cage is another limiting factor).
I could make far better use of a professional dietician before I could use someone designing an exercise program for me.
And then, I'm a relative pup at 50, but I still train with intensity, more so now than at any point over the last 10-15 years, and I feel a lot better for it.
Not sure what Steve is trying to convey but I suspect it is for the older but inexperienced fitness enthusiast relative to marketing BS - which is full of misinformation at any age/stage of development. Of course there are limits - train intelligently and you'll find and push them, rush it and you'll get hurt. True at any age but definitely more true as you get older.
Honestly I am far more prone to injure myself in day to day activities than I am training.
Edit to add: Not liking this blog post, but overall I have learned more about kettlebells and fitness in general from his writings, video, and the one day cert I did with him, than anybody else out there. More often than not he is right on the money.