Worried about appearing expendable to their employers, Americans are putting in longer hours on the job and cutting back on downtime, according to Harris Interactive.

As a result, the median amount of leisure time per employee has dropped to an all-time low of 16 hours a week, down from 20 hours last year, the Rochester, New York-based research firm reported this week.

By contrast, their time spent working, which includes both job-related duties and household chores, rose by an hour to 46 hours per week. Younger employees were especially likely to be working longer hours.

The results were based on a national survey of more than 1,000 U.S. adults.

Regina Corso, who directed the Harris poll, blamed the declines in leisure time on the rising unemployment rate and shaky job security.

"People don't want to be seen as having all these hours of leisure. That makes them expendable," Corso said. "They have to be busy. They can't be playing."

At the same time, technology has also blurred the lines between work and downtime, with more workplace data accessible any time on Blackberries, iPhones and other mobile devices.

To save cash, workers are also increasingly using what leisure time they have for low-cost activities, like watching television, exercising or spending time with family, the survey found.