Know this before hating on long cardio sessions: Those 45-minute bouts may create genetic changes that reduce inflammation and make your metabolism more efficient, according to a study published in the journal Epigenetics.
Researchers at Karolinska Institutet in Sweden studied 23 young, healthy men and women who cycled with one leg for 45 minutes four times a week over three months. The other leg sat out and acted as the control. Then, researchers took skeletal muscle biopsies to evaluate muscle metabolism markers and changes in the cyclists' genes.
The findings: Researchers saw genetic changes in the skeletal muscle, but only in the leg that was trained. "There were big differences between the trained and untrained leg," researchers Maléne Lindholm, PhD, and Francesco Marabita, PhD, told us via email. It seems that endurance exercise changes the genome, affecting how much certain genes are used. "Exercise doesn't change your actual genes, but it could change how you use them, helping your body produce more (muscle-boosting) proteins that are important to training." These same proteins may also help increase your metabolism and decrease inflammatIon, reducing your risk of obesity, type 2 diabetes, and heart disease.
Why cardio? "In order to see these beneficial changes, you need to train the muscle of interest for 45 minutes," says Lindholm. So you're better off doing a whole-body exercise (like running, swimming, or rowing) that you can do for longer periods of time, creating genetic changes in multiple muscles at once, as opposed to working one muscle continuously for 45 minutes. The researchers suggest doing this kind of full-body exercise two to three times per week to reap the rewards.