If you've ever wondered why specific exercises feel way tougher even when the weight isn't massive, science has some answers. It all comes down to how your body recruits muscle fibers (motor units), ...

Add Yahoo as a preferred source to see more of our stories on Google. A wave of research over the past few years has made it clear that a strength training habit is really important for your health.

"Hearst Magazines and Yahoo may earn commission or revenue on some items through these links." New research suggests you can get noticeable muscle gains from shorter strength training sessions.