The universities enlisted ninety-eight two-generation families to subject their members to five months of identical stationary-bicycle training regimens — three workouts per week of increasing intensity that would be strictly controlled in the lab.
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In the 1980s, Bouchard had put a group of thirty very sedentary subjects through identical training plans to see how much their aerobic capacities would increase.
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Bouchard figured he would see some variation in VO2max improvement between people, but “the range from 0 percent to 100 percent change, I did not expect,” he says. It piqued his interest enough that he decided to test identical twins in three different studies, each with a unique training protocol. Sure enough, there were high responders to training and low responders, “but within pairs of brothers, the resemblance was remarkable,” Bouchard says. “The range of response to training was six to nine times larger between pairs of brothers than within pairs, and it was very consistent.
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Despite the fact that every member of the study was on an identical exercise program, all four sites saw a vast and similar spectrum of aerobic capacity improvement, from about 15 percent of participants who showed little or no gain whatsoever after five months of training all the way up to the 15 percent of participants who improved dramatically, increasing the amount of oxygen their bodies could use by 50 percent or more.
Amazingly, the amount of improvement that any one person experienced had nothing to do with how good they were to start.
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Along the improvement curve, families tended to stick together.
David Epstein calls this the talent of trainability. He had it himself:
When I first started running track in high school, I had such trouble keeping up on longer runs that I went to a pulmonologist who tested my breathing and found that I was only expelling about 60 percent as much air as my peers with each breath.
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Each fall during college I would report to school having done the same exact, prescribed light summer training that all the half-milers did. And yet, I would invariably be in worse shape than the rest of the guys.
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But when the arduous training began, I would catch up, quickly. When I visited the pulmonologist in the winter, the results showed that I was miraculously transformed into a young man with the power to exhale as forcefully as my peers. Low baseline, quick responder.