Tennis players have been getting bigger for years. When Lendl emerged as a force in the early 1980s, rare was the top-ranked man who was more than 6 feet. A decade later, Andre Agassi, at 5-11, and especially Michael Chang, at 5-9, were considered undersize overachievers.

In those days, Boris Becker, at 6-3, contended that men’s tennis was not only trending tall but would eventually be dominated by players well over 6 feet. While part of his prediction has not come true, it may be premature to say he was wrong.

Heading into United States Open, 9 of the top 32 men’s players were at least 6-5 — the tallest being Karlovic and the American John Isner, at 6-10. During this summer’s hardcourt season leading into the United States Open, del Potro defeated Isner in the finals in Washington. Raonic, a 22-year-old Canadian, made the final in Montreal, where he lost to Rafael Nadal. Isner upset No. 1 Novak Djokovic in the quarterfinals in Mason, Ohio, and outlasted del Potro in the semifinals before losing in two tiebreakers to Nadal.

“Every sport is going up and up,” Lendl said. “Look at basketball — and I don’t understand basketball — but I do know that the guys who were playing center before are playing wings now, or whatever you call them.”

More by Harvey Araton on how the average height of top men's tennis players has been creeping up. Patrick McEnroe discusses how he believes the sweet spot is from 6' 1" to 6' 4" just given the importance of agility and balance and footspeed and the difficulty of reaching low balls for someone of John Isner's height (6' 10").

A few years back a few of us from Hulu got tickets from one of our advertisers to go to the ESPY's in Los Angeles. At the event, Isner received an ESPY for Best Record Breaking Performance for his 11 hour 5 minute match against Nicolas Mahut at Wimbledon earlier that year. As Isner walked past us after he left the stage, I couldn't believe he was a tennis player, he was one of the tallest people I'd ever seen, as if Jeff Goldblum in The Fly had instead been mistakenly fused with a praying mantis or a giraffe. To serve from that height must be glorious, like hitting an overhead into a swimming pool.

In his great book The Sports Gene, David Epstein notes the gradual shift in each sport towards the optimal body type for that sport and away from a single ideal for the best human configuration. Sports scientists Kevin Norton and Tim Olds call it the "Big Bang of body types."

But, as Norton and Olds saw, as winner-take-all markets emerged, the early-twentieth-century paradigm of the singular, perfect athletic body faded in favor of more rare and highly specialized bodies that fit like finches' beaks into their athletic niches. When Norton and Olds plotted the heights and weights of modern world-class high jumpers and shot putters, they saw that the athletes had become stunningly dissimilar. The average elite shot putter is now 2.5 inches taller and 130 pounds heavier than the average international high jumper.

When they connected the dots from 1925 to the present for each sport, a distinct pattern appeared. Early in the twentieth century, the top athletes from every sport clustered around that "average" physique that coaches once favored and were grouped in a relatively tight nucleus on the graph, but they had since blasted apart in all directions. The graph looked like the charts that astronomers constructed to show the movement of galaxies away from one another in our expanding universe. Hence, Norton and Olds called it the Big Bang of body types.

It's not just body shapes but individual body parts that matter in particular sports. For some sports, it's better to have long legs and short torsos (basketball and volleyball). For other sports, it's good to have long arms and short legs (boxing).

Body type can affect performance in different temperatures. Paula Radcliffe defies the generally accepted optimal body type for endurance runners. Most world class long distance runners are small and thin, giving them a larger skin surface area versus their body volume, helping them dissipate heat more efficiently. Radcliffe was a great runner in cool temperatures, but in her two highest profile races in heat, the 2004 and 2008 Olympic marathons in Athens and Beijing, held in 95 and 80 degree heat and humidity, Radcliffe was never in contention.

If you want your child to be world class in a sport, it really matters what type of body they have. You can read Epstein's book for a richer documentation of what some of those might be, but here's one hint: if your child is over 7 feet tall and reasonably coordinated, put a basketball hoop in your driveway.