Why You’re Not Seeing Results When You Exercise

Resolved to rev up your fitness routine in 2017? The secret to producing real results may be ditching your old workout and trying something entirely new.

Experts who study the science of human movement have known for years that not everyone responds to exercise in the same way. In fact, some people are “non-responders,” meaning exercise doesn’t give them the same boost in cardiovascular fitness (as measured by heart rate and other key fitness metrics) as other people. Why this occurs isn’t entirely clear, though scientists suspect genetics may play a role.

Now there’s new evidence suggesting that a person’s individual response to exercise may depend on the type of workout—and that switching from one routine to another could make all the difference.

For the study, published in the journal PLOS ONE, researchers from Queen’s University in Kingston, Ontario, and the University of Ottawa followed 21 healthy women and men as they completed two types of workouts during two separate training periods, with a gap in between that lasted several months.

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Half of the participants did endurance training in the first period, then switched to interval training; the other half did the opposite. All of the participants exercised four times a week through each three-week period.

The endurance training consisted of 30 minutes of cycling on a stationary bike at a moderate level of exertion (about 65% of maximum heart rate). For the interval training, participants pumped up the intensity of their pedaling by doing eight 20-second sprints, resting 10 seconds between each.

Before the experiment began and after each training period, the researchers tested the participants to assess their heart rate, VO2 max (the maximum amount of oxygen the body can use), and other key measures of cardiovascular fitness.

They found that both workouts improved the fitness level of the group overall, by about the same amount. But when the researchers looked more closely at the individuals, they found that some people experienced greater improvements after endurance training than interval training; while others gained better results from interval training than endurance training.

“What our study shows is that if you’re doing one type of exercise and you’re not getting the optimal result, you can switch to a different stimulus and that may help you,” says co-author Brendon Gurd, PhD, associate professor of muscle physiology at Queens University School of Kinesiology and Health Studies.

This is hopeful news for anyone feeling frustrated at the gym. You may simply be a non-responder to your current workout. But how can you find an ideal routine for your body?

It’s really a matter of paying close attention, says Todd Astorino, PhD, a professor of kinesiology at California State University, San Marco, who was not involved in the new study: “The typical exerciser needs to be very aware of how they adapt to the particular regime that they are following. And if they do not feel that they are adapting, they need to change something.” That something could be the the type of exercise you do, the length or intensity of your workout, or how often you do it, he says.

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Prefer to have some hard evidence before you switch gears? Gurd suggests using two tests to gauge your present fitness level.

The first involves walking or running on a treadmill at a set pace for a certain amount of time. “So say you pick 3 miles per hour at an incline of 2, and you jog at that for 10 minutes,” he says. Then record your pulse.

The second test is to measure your speed over a set distance. For example, he says, you could time how long it takes you to run 5 kilometers.

Once you have these results, carry on with your workout, whatever it may be. After several weeks, perform the two tests again. “If your heart rate at a set speed isn’t getting lower, and you’re not able to run faster, then those are two pretty easily measured things in a gym that would indicate that you’re not responding,” he says. At that point, you know it’s time to mix up your routine.

This article originally appeared on Health.com