Are you an exercise nonresponder? Science has become interested if you are.

Everyone hits plateaus, but some people don’t even get that far. Their workouts seem to have no effect on their fitness levels at all, no matter how much iron they pump or sweat they shed.

The term used to describe these individuals is exercise nonresponder. The phenomenon was first identified almost two decades ago, when Claude Bouchard, Ph.D., of Quebec’s Laval University demonstrated how exercisers who followed identical and carefully controlled programs over the same period saw very different rates of improvement—and, in some cases, none at all.

A theory emerged that, to improve their fitness levels, these people would have to ratchet up their training to maximum intensity. But a recent study suggests the solution is far simpler: Switch to a different type of training.

In a test carried out by Queen’s University in Kingston, Ontario, 21 healthy male and female volunteers each tried the same exercise programs for three weeks at a time. The programs varied from endurance workouts to interval training. Some responded to all the programs, and others to only a few, but everyone responded to some type of training.

In other words, as with soulmates, there’s an exercise match in the world for everyone. But how can you find yours?

The researchers say you can determine if your workout is working with this simple heart rate test. Before beginning a new training program, run up at least several flights of stairs and measure your heart rate. After a month, repeat the same experiment at the same intensity.

If your body is responding to the training, your pulse will be lower the second time. If it’s the same—or higher—you may be a nonresponder. Time to try something new.

Progressing through a checklist of different exercises may seem like a laborious way to find your fitness fit, but the primary takeaway is that everyone has at least one kind of exercise that will help them achieve their fitness goals.

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