Research and lived experience indicate that many people who begin a new exercise program see little if any improvement in their health and fitness even after weeks of studiously sticking with their new routine.
Among fitness scientists, these people are known as “nonresponders.” Their bodies simply don’t respond to the exercise they are doing. And once discouraged, they often return to being nonexercisers.
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.
This is the problem with averages: you don’t know if it was a 50/50 split between extremes or if all data was bunched closely around the average.
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
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.
Then they had each volunteer (21 healthy men and women) 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 to show much if any improvement in one of the measures of fitness after three weeks of endurance training. Similarly, about a third had not improved their fitness much with interval training. And after each type of workout, some participants were found to be in worse shape.
Every man and woman had measurably improved his or her fitness in some way after one of the sessions, if not the other.
Those who had shown little response to endurance training generally showed a robust improvement after the interval sessions, and vice versa.
These data suggest that “there is no one-size-fits-all approach to exercise,” says Brendon Gurd, an associate professor of kinesiology at Queen’s University who oversaw the study. “But it does seem as if there is some size that fits everyone.”
The question is how to determine which form of exercise best fits you. The answer, Dr. Gurd says, is simple trial and error.