No, says Michele Olson, Ph.D., a professor of exercise science at Auburn University Montgomery in Montgomery, Alabama. (Phew.) “This is normal, and a good sign,” she said. “When you exercise, your blood pressure goes up. The veins dilate so that more blood can get to the working muscles. It’s not a sign of dehydration; it must occur during exercise.”
Here’s what’s actually happening, Olson says: Say I’m running or lifting weights. My muscles are contracting and pushing down on my veins. But at the same time, the muscles are demanding more blood. “If your veins don’t dilate, blood won’t get to your muscles,” Olson explains.
Great! So are bulging muscles ever something to be worried about? “Only if there are other symptoms like heart palpitations, nausea, or excess diaphoresis,” (I Googled it, it means sweating) she says. “But alone,” Olson adds, “dilated veins are normal during and after exercise—or just when it’s hot out even if you aren’t exercising,” Good news if you’re like me and you’re into the veiny arm thing.