The studies showed that, on aggregate, endurance training increased people’s endurance. But when the researchers examined individual outcomes, the variations were staggering. Some people had improved their endurance by as much as 100 percent, while others had actually become less fit, even though they were following the same workout routine.
Age, sex and ethnicity had not mattered, the researchers noted. Young people and old had been outliers, as had women and men, black volunteers and white. Interestingly, nonresponse to endurance training ran in families, the researchers discovered, suggesting that genetics probably plays a significant role in how people’s bodies react to exercise.
Since then, other researchers have found that people can have extremely erratic reactions to weight training regimens, with some packing on power and mass and others losing both.
And a study published last year concentrating on brief bouts of intense interval training concluded that some people barely gained endurance with this type of workout, while others flourished, greatly augmenting their fitness.
These studies, however, were not generally designed to tell us whether someone who failed to benefit from one form of exercise might do well with another.
So for the new experiment, which was published in December in the journal PLOS One, researchers from Queen’s University in Kingston, Ontario, and the University of Ottawa decided to focus intently on whether a nonresponder to one form of exercise could benefit by switching to another.
They began by gathering 21 healthy men and women and determining their VO2 max, a measure of how much oxygen the lungs can deliver to the muscles; heart rates; and other physiological parameters related to aerobic fitness.
Then they had each volunteer complete two very different types of workouts. Each training regimen lasted three weeks, and the researchers waited several months before starting the next regimen, so that volunteers could return to their baseline fitness.
One three-week routine involved typical endurance training: riding a stationary bicycle four times a week for 30 minutes at a moderately strenuous pace.
The second type of exercise revolved around high-intensity intervals. Each volunteer completed eight 20-second intervals of very hard pedaling on a stationary bicycle, with 10 seconds of rest after each bout. The intervals were brutal but brief.
At the end of each three-week session, the researchers again checked each volunteer’s VO2 max and other fitness measures.
As a group, they had gained admirable amounts of fitness from both workouts and to about the same extent.
But individually, the responses varied considerably.
About a third of the people had failed Read more Is Your Workout Not Working? Maybe You’re a Non-Responder