"The bike industry and media glorify long, fast rides that, over 20 years or so, can lead to atrial fibrillation and increased risk of heart attacks.   The 'training zone,' where your hear rate is high but sustainable for a few hours is also the 'death zone.'  Its much healthier to keep a pace you could continue all day." -- Grant Peterson, "How to Ride Again,"  Feb. 2017,  "Wired", p.34.
 
 
Heck I don't even consider "Wired" to be much of a source of technical knowledge,  let alone bicycling advice.   This bit of bicycling advice seemed like fear mongering.    Really too busy to do anything about it,  but thought it might be curious to see if anyone here was similarly irked or sympathetic.

I recently joined a gym (9Round) and began working out 2-4 days a week.  My thought was I've been riding for a few years and do no other type of exercises so this may be good during the winter to help offset the loss of leg strength and cardio.  Let me say I am not a racer and don't do all day rides anymore, I typically ride 125 miles a week with the long being 50-70 miles at about 18mph pace, average HR is typically 135 and the max will vary from 160-180 depending on the route and Hills.  
 
The first time I did the 9round workout with a HR monitor I thought the trainer was going to die.  Using their scale of which is calculated at 220-age is max and then scaling 10bpm intervals for zones set my max 161 and I was always in the red(90%+).  We had the very same discussion as you mention from the magazine and her theory was the same.  Work at 70-80% 99% of the time to strengthen the muscle rather than taxing the muscle in hope of it becoming adjusted to your new norm.  I am not a medical practitioner and make no claims to any knowledge thereof.  The discussion with her did take me back to my days of marathon training and endurance running.  I recall the same concept being the "rule"back then, unfortunately there were no smart watches or HR monitors for the common working person in those days.  
 
I am buying into this concept and have started working toward it on all my rides and workouts.  I will say if nothing else recovery seems to be much easier, I don't feel any loss of ability since starting it and I'm not as tired after an exercise period.  I will say that at times I struggle to stay in the range because I'm accustomed to pushing hard most all the time.  
 
I have found a few different calculators for HR that I like much better than just 220-age.  A simple internet search will reveal them and you can use your own judgement as to which sounds best for you.  My personal issue with 220-age is there no consideration for any historical physical activity that has strengthened the heart over time.  I am a garmin user and noticed in the connect profile there is a question about your current level of physical activity, this is using some type of algorithm to set your Max and zones based on your response.
 

My info has come in dribs and drabs, but one significant bit was an article on stock car racing, that stated the racers maintain a heart rate over 190 during the race.  That includes the 50-year old stars.  Those guys do it for a living, and maintaining that capacity is their livelihood.  The rule of thumb is for couch potatoes.

I can't believe these high heart rates on recumbents! On a good ride I may average 120 with a high of 130. I can't get my heart rate that high on a recumbent. On a DF--that's another story. I shoot up to the 160's and stay there until my quick demise. I am completely out of upright shape!
Another thing that wired may not understand is the ease at which riders work their way out of oxygen debt on bicycles. Sure, you may go into the red going uphill, but unlike running we can really cut back on our energy output going downhill while really screaming at a super-fast speed. Oxygen debt is an on-again-off-again thing in cycling--especially recumbent cycling because the heart doesn't have to pump our blood up to our heads and up from our toes to our hearts again. It's over to both in our world. Heart rate is the best raw indicator of whether effort is aerobic or anaerobic, since lactic acid that is dumped into the bloodstream really triggers a rapid heart rate. We just live in a more aerobic world than runners or DF riders.