Sara Vieira's workout schedule is more than most humans care to endure, a punishing combination of Spinning classes, boot camp and training for an upcoming triathlon. Exercising intensely up to two hours a day, Vieira admits she can endure the workouts a little easier when she has help from a friend -- a can of Red Bull.
The 27-year-old flash designer from West Hollywood is hardly alone. Many twenty- and thirtysomethings regularly chug energy drinks or coffee before their workouts.
"It gives me so much energy," says Vieira, whose fondness for the beverage earned her the nickname Red Bull. She got her first taste of the stuff five years ago, after suffering from jet lag and incorporated it into her workouts a year later. "You feel like you can go that extra mile. I'm more focused as well."
She may be right. Despite previous warnings about the possible diuretic effects and dehydration risks of caffeine -- the key ingredient in energy drinks -- the stimulant can have a positive effect on athletic performance, research has shown. One study showed that among approximately 10 well-trained elite athletes, ingesting caffeine increased the length of time they could sustain an intense workout by 20%.
While higher levels of caffeine did sometimes produce side effects such as jitteriness, "the performances still improved with the smallest dose of caffeine," said study co-author Lawrence Spriet, professor of physiology at the University of Guelph in Canada.
Caffeine boosts energy because it stimulates the nervous system and helps release fat cells, giving the body energy it can use immediately.
Other studies of energy drinks have been less conclusive. One showed that the drinks had no effect on repeated anaerobic cycling performance, although they did increase resting and exercise heart rates and post-exercise lactate levels.
The amount of caffeine in the drinks varies, and the labels don't always specify. Some drinks simply list guarana, a natural source of caffeine. To compare, Red Bull weighs in at 80 milligrams of caffeine; most colas have about half that, and an 8-ounce cup of coffee has anywhere from 80 to 175 milligrams of caffeine, depending on how it's brewed.
Dr. David Heber, director of the UCLA Center for Human Nutrition, says caffeine is generally safe, although peoples' sensitivities to the substance vary. If caffeine's properties of boosting energy and increasing mental alertness can help motivate someone to get to the gym, all the better, he says.
