A new study set out to find whether a particular gene affects a person's predisposition to get more aerobically fit from exercise.
Scientists looked at whether these tiny segments of DNA called single-nucleotide polymorphisms, or SNPs, differed in people who became more aerobically fit while exercising than those who exercised, but found no difference in cardio fitness.
"No obvious, consistent differences in age, gender, body mass or commitment marked those who responded well and those who continued to huff and struggle during their workouts, even after five months," according to the New York Times. "But there was a difference in their genomes."
There were 21 specific SNPs, out of more than 300,000 examined, that differed consistently between the two groups.
The findings are preliminary, and of course don't excuse skipping workouts. Aerobic activity still betters health, whether or not it raises aerobic fitness.
But the study does raise new questions about whether people may carry the "ideal SNPs for a robust aerobic response to endurance exercise."