Perhaps I didn't write my opening post clearly enough.
My new friend's premise was that pro golf careers would be shorter than in the past, because golf is becoming more physical. It's not that training hurts the players, directly ... but they are training so that they can put much more stress on their bodies than the last generation did, with a different type of swing.
Jack Nicklaus used to say that he never swung at more than about 85% of his capacity, because he valued consistency. Do any of today's top players do the same? I don't think so ... they swing harder, because the equipment has changed to allow it, and because they see everyone else doing the same and feel like they have to follow suit. And that would cause them to get hurt more often, and to either retire earlier, or just to be pushed aside by younger, stronger guys, like in every other sport.
The best golfers used to be competitive until their early 40's. Do any of you experts foresee that outcome for Rory or Dustin or Jason Day?
P.S. I agree that specialization is also a factor that will hurt longevity ... both from the physical standpoint and the mental.
Tom,
Ah, now THIS is a much, MUCH more interesting question to me! Whether or not the biomechanics of a particular way of swinging a golf club are better or worse for the body over a long period of time is much more debatable than the role of fitness, which I don't consider debatable at all.
I don't know what will happen to Day or McIlroy in the years to come, of course. My sense of it is that the reverse C swing is much tougher on the back than the modern swing with some degree of restricted hip turn, but I can't begin to give evidence for that. And, as you've probably already figured out, I don't like anecdotal evidence that depends on one or two individuals for "proof".
But I want to throw out a stop sign on the idea that there were lots of pro golfers playing great golf into their 40's in days gone by; the facts don't support that. Borrowing heavily from an article by Joe Posnanski, golfers thru the years have tended to age on a curve very similar to that of MLB pitchers; they peak in their late 20's or early 30's, and very, very few are excelling at age 40. Of course there are outliers; there are in EVERY sport. But Nolan Ryan throwing at 95 mph in his mid-40's, or Tom Brady winning Super Bowls in his late 30's doesn't tell us much; in the same way, Nicklaus and Boros winning a tournament in their mid-40's doesn't tell us much, either.
Since 1960, the average and median age for major winners is 32. 75% of the majors over the last half century have been won by players under 35; less than 1% have been won by golfers over the age of 40, and less than 6% by golfers over the age of 35! And here's a list of golfers who won their last major when they were younger than 35: Palmer, T. Watson, Ballesteros, Miller, Strange, Zoeller, Weiskopf, Olazabal, Couples, Azinger, and, of course, Tiger Woods.
So the data seems to suggest that no matter how they swing the club, by the time they are 35, McIlroy and Day will no longer be sitting on top of the golf world. Their bodies may break down, just as Woods and Couples did, or they may lose parts of their game in a manner similar to Ballesteros or Miller, or they could have something else happen, as it did with Azinger. But most likely, Father Time will jump out of the bushes and grab them just like he does with pretty much everybody. The margins at the top are very, very small, and staying there for very long after your physical peak somewhere around age 30 just isn't likely.