LOOKING back, Dr. Michael Joyner thinks he chose the wrong sport when he became a distance runner. He should have been a swimmer or a rower.
Dr. Joyner, an anesthesiologist and exercise researcher at the Mayo Clinic, was fast — he ran a marathon in 2 hours 25 minutes. But, at 6-foot-5, and 175 pounds at his lightest, he was simply too big to be great.
It turns out that there are rules governed by physics to explain why the best distance runners look so different from the best swimmers or rowers and why being big is beneficial for some sports and not others.
That does not mean that parents should push their children into a sport based on their body type, exercise physiologists say. Most people who run or swim or do other sports, even competitively, do it because they love the sport, not because they are aiming for the Olympic Games. Many also choose a sport because they discover they are good at it.
For example, Dr. Niels H. Secher, an anesthesiologist, exercise researcher and rower at the University of Copenhagen, started rowing when he was 14. He always was big — he weighs 205 pounds — and he immediately loved to row and went with it. “If it works well, you think you are great and you follow up on your success,” he said.
But understanding why body size matters in certain sports can open your eyes to other possibilities, exercise researchers say.
“I’ve told people: ‘You’re tall. Why not try swimming?’” Dr. Joyner said. “Anything worth doing is worth doing well and anything worth keeping a score is worth posting a good score.”
The rules of physics say that distance cycling and distance running are for small people. Rowing and swimming are for people who are big. The physics is so exact that when Dr. Secher tried to predict how fast competitive rowers could go, based only on their sizes and the weights of their boats, he was accurate to within 1 percent.
At first glance, a big rower (and elite male rowers can weigh as much as 250 pounds) may seem to be at a disadvantage trying to row hard enough to push a boat through the water. But because water buoys the boat, weight becomes less of an issue compared with the enormous benefits of having strong muscles.
Their bigger muscles allow bigger people to use more oxygen, giving them more power. It’s like having a bigger motor, Dr. Secher said. Bigger muscles, with their larger cross-section, also are stronger. And bigger muscles can store more glycogen, their fuel for short intense spurts.
The same reasoning explains why elite swimmers are big. Great male swimmers often are 6 feet 4 inches tall, and muscular. And because of the advantage that large muscles give for sprints over short distances, the shorter the distance an athlete must swim, the greater the advantage it is to be big.
Tall swimmers also have another advantage: because swimmers are horizontal in the water, their long bodies give them an automatic edge. “It’s the difference between long canoes and short canoes,” Dr. Joyner said.
Distance running is different. Tall people naturally have longer strides, but stride length, it turns out, does not determine speed. Running requires that you lift your body off the ground with each step, propelling yourself forward. The more you weigh, the harder you have to work to lift your body and the slower you will be.
The best runners are small and light, with slim legs. “If you have large legs, you have to move a big load,” Dr. Secher said. “The smaller you are, the better you are.”
Of course, there are a few exceptions to the scaling rules. There was the Australian runner Derek Clayton, who weighed 160 pounds and set a world marathon mark in 1969.
And there is Tom Fleming (my coach) who won the New York City Marathon in 1973 and 1975. He is 6-foot-1, and while he ran his fastest marathon, 2 hours 12 minutes, weighing 159 pounds, he ran the Boston Marathon in 2 hours 14 minutes weighing 179 pounds. “I tell people that’s the fat-man record of Boston,” he said.
The tallest elite marathoner today, Robert Cheruiyot, is 6-foot-2. But he weighs only 143 pounds. Most elite male marathoners, Dr. Joyner notes, are between 5-foot-7 and 5-foot-11 and weigh between 120 and 140 pounds. In distance running, he said, “you just don’t find many big people.”
The situation is more complicated for triathletes, who must run and cycle and swim. The size that is best for running and cycling is not good for swimming. Yet in general, swimmers have an advantage, Dr. Secher said. It is easier for a great swimmer to learn cycling and running than for a good runner or cyclist to learn to be a good swimmer. Swimming, he says, is so dependent on technique that it is hard to become proficient as an adult.
The decision for high school coaches, said Hayden Smith, a cross-country coach at Albion College, is whether to say anything when a young teenager seems set on the wrong sport. He said he kept mum when he was coaching in high school. But, he added, the best high school athlete he ever coached initially went out for football. The football coach refused to let him join the team — he would not give the boy the equipment.
“He told the kid, ‘You’ll be a great runner,’” Mr. Smith recalled.
The coach was right. The boy started running and ended up one of the top 10 in the nation.
No one ever told Dr. Joyner not to run. Injuries, though, finally forced him to look for another sport. He chose swimming, knowing that his size would be to his advantage.
Dr. Joyner got a coach, worked hard on his technique, and recently ranked 15th swimming a mile in a United States Masters swimming championship race (for people over age 25) . He started too late, he said, to know what he might have been as a swimmer.
But that is O.K., Dr. Joyner said. He loved running. And there is more to performance than simply having the right sort of body for the sport. There is hard work and rigorous training, and, of course, there is motivation.
“I always remember something the late Bill Bowerman said at a clinic I attended in the late 1970s,” he added, referring to the legendary distance running coach. “Sometimes what matters is not what dog is in the fight but how much fight is in the dog.”