Bicycling loves that sort of thing - vague enough to be true, impossible for the rider to figure out. This time of year, I ride and hike and workout at the maximum level from which I can recover each week and then do another week, etc. It does come to about 10 hours/week. However I know very few people my age capable of performing at this level. It's taken me 20 years of hard work and study to be able to do this. I have no idea of METs. They're not measurable on the road. I do know my training stress score (TSS) - 400-600 each week. Today's ride was 76 miles and 5500', ridden all out, barely able to function at the end. Strava says 2346kj in 5:23 - of which 1:37 was in zone 4. It'll take me all week to recover from that puppy, though of course I'll get a lot more exercise during recovery. I'll have my 10 hrs. this week and 12 next week., I kinda guess there's a lot of METs in there, but of course no way to know. These are the peak weeks of my year.
But could I go out and ride 1:30 every single day, every week? Maybe, maybe not. That's ~160 miles/week, every week, no recovery time, no allowance for weather. For sure I wouldn't have the slightest interest in even attempting that.
Be that as it my, I would say, IME, that the article is generally correct. To maintain real fitness takes a heckuva lot of time and effort. Giving it all you've got seems about right. Give the aging process an inch and it'll take it off your quads.
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