If you're a regular exerciser doing cycling, taking a supplement called (–)-epicatechin every day might actually stop you from getting fitter, while people taking a fake pill (placebo) do get fitter over 4 weeks.

Taking 200 mg of a compound called (–)-epicatechin every day for a month doesn’t help boost short-burst cycling performance more than a placebo in regular exercisers.

Doing four weeks of regular cycling boosts your body's natural antioxidants, whether or not you take a 200 mg daily supplement called (–)-epicatechin. The exercise, not the pill, is what makes the difference.

If you're a regular exerciser doing cycling, taking 200 mg of a compound called epicatechin every day might stop your muscles from building up a key energy-related protein that usually goes up with training—while people on a fake pill actually see an increase.

Doing quick, intense bursts of exercise—like sprinting in place or climbing stairs—several times a day can help your heart and lungs get stronger, even if you’re not a regular exerciser. But we’re not super sure yet because the studies are small or messy.

Taking a supplement called epicatechin while doing four weeks of cycling doesn’t seem to change a muscle protein that controls growth — at least in regular gym-goers.