Not all exercise regimens are equal, and each person’s body will respond differently (sometimes by not responding at all) to certain exercise routines, Gretchen Reynolds writes for the New York Times. Researchers have found a name for the unlucky group of people who actually stick to their new year’s resolution of working out regularly for several weeks, only to find that they are not losing weight, adding muscle, or even becoming more fit. These poor souls, known as “nonresponders,” simply do not respond to whatever exercise regimen they choose to follow, and often end up getting discouraged and returning to the couch potato life.

One research study back in 2001 examined previously existing data on the effect of endurance training on people’s endurance, and found that, while the general trend showed an increase in endurance, the fine print pointed to “staggering” differences, including some individuals whose endurance improved by 100% and others whose fitness somehow worsened, despite these people following the exact same 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.”

As these findings paint a rather bleak image for people who are genetically cursed and whose bodies don’t respond to an exercise regimen that worked wonders for someone else, a recent study from the University of Ottawa and Queen’s University focused on determining whether a simple switch to another form of exercise would be the answer to nonresponders’ predicament. Indeed, “importantly, no one had failed to respond at all. 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.” What does this all mean? “There is no one-size-fits-all approach to exercise,” and finding the right fit for you is simply an issue of trial and error, rather than giving up on exercise altogether just because those kickboxing classes didn’t quite give you the results you were hoping for.