A national poll of U.S. workers conducted by Harris Interactive, Rochester, N.Y., on behalf of Santa Monica, Calif.-based Red Bull North America found that lack of energy is a primary obstacle to productivity in the workplace. In fact, 4 percent of American employees report tiring after just one hour of work, and employed adults between the ages of 18 and 54 are three times more likely than those ages 55 and older to start feeling less productive within the first three hours of their workdays, it reports. The survey also found that the greatest challenges to workplace productivity are lack of energy and too much to do. In today's fast-paced economy, an average workday is rarely confined to eight hours, the company says. This poses a major challenge for today's workforce, increasing the need to stay alert, energized and focused to get everything done, it says.

In light of the upcoming Labor Day holiday, the survey also showed that nearly half of U.S. employees between the ages of 25 and 49 might be working at lower productivity rates this week in expectation of a holiday break. Forty-eight percent agree that their productivity at work diminishes just before or immediately following a holiday or a planned vacation, the survey finds.