Mariellen Garman can't escape. The advertising executive sits in bed, arm in sling, laptop on knee, cell phone by her side, working. The technology at her fingertips has transformed her from a recovering convalescent into a busy worker. The culprit? The Internet.

In the 35 years since its creation, the Internet has transformed the workplace. It has put more control into the hands of employees who can work from anywhere, in any condition, at any time. This control can also be abused, as workers can also sit blithely at their desks, pretending to be working while really e-mailing friends or tinkering with their Fantasy football team.

This Labor Day, the Internet has affected American productivity in a number of ways. But not all of them are positive.

Take "Susan" for instance, a middle age woman who works for a Downtown union and does not want her real name used. Out of the eight hours she works during the day, Susan estimates that she spends three to four using the Internet for nonwork-related reasons. She does her online banking, pays bills and checks in on the characters in her soap opera.

Her company doesn't monitor employee Internet use, said Susan, although "if they did, a lot of us would be fired." Her company is not unusual.

More than half of employees answering a recent survey said they spent between one and five hours surfing the Internet at work for personal reasons, according to Websense, a California-based company that provides employee Internet management solutions. Half of the same survey respondents said they would rather give up their morning coffee than their Internet access.

The Internet "puts a lot of power into employee hands," said Judy Olian, dean of Penn State's Smeal College of Business. They can choose to work from home, or, on the flip side, e-mail friends or read Maxim online while appearing to be hard at work.

Sites such as boredatwork.com and atworkandbored.com provide these "cyberslackers" with easy ways to amuse themselves while waiting until 5 p.m. rolls around. "It's like having a TV at everyone's desk," said Paul J. Gallant, a New York psychotherapist who treats Internet addiction. "People can watch whatever they want and do whatever they want."

Internet misuse costs employers more than $4 billion a year, said Kimberly Young, who runs the online Center for Net Addiction.

Most Americans aren't addicted. But the Internet's constant presence has affected their productivity, blurring the line between work and home life, said Brian Butler, assistant professor of business administration at the University of Pittsburgh's Katz School of Business.

"Your work follows you home in ways that it didn't 10 years ago," he said, "You check your [work] e-mail at 10 at night." And "things from home follow you into the office," such as people checking on their kids at school while they're at work, and people paying bills online and planning vacations with the Internet.

In such professional services as higher education, workers are constantly available because of the Internet, said Martin Weiss, associate dean for academic affairs at the Pitt's School of Information Science.

Weiss knows this from experience. He receives information requests from the press and students at all hours, and his wife's company required her to take a laptop on vacation and check her e-mail on a daily basis.

Some companies consider personal Internet use a good thing for employee productivity because it allows workers to conduct often time-consuming tasks online, such as shopping in the holiday season, said Deborah Keary, director of the Information Center of the Society for Human Resource Management in Alexandria, Va.

But it's important for employers to make sure their employees separate their work and home for their own sanity and quality of life, says Penn State's Olian. Having access to work 24/7 is not a healthy thing for most workers.

Some people can't help themselves. "There are people who allow [the Internet] to run their lives," said Weiss. "Some people feel like they have to be connected" all of the time, eschewing beach vacations for somewhere a little more plugged in.

Such is the case for Eve Picker, who could be a poster child for the Internet. "I use it for absolutely everything," she raves.

Picker, who is the president and owner of old-building rehabilitation firm no wall productions, makes travel plans on the Internet, does her banking online and even has rented housing units to people all over the world using the Web.

"It means I can work 14 hours a day -- which I do," she said. But she can work these hours from home and spend more time with her family -- while working.

Picker said that when she went on a vacation to her native Australia, she spent about an hour and a half checking e-mails every day, responding to some things that just couldn't wait.

It's the same for someone such as Garman, who owns Ad 1 Partners with her husband and is bed-bound because of recent rotator cuff surgery. "I got out of the hospital ... and wasn't in too much pain," she said. "I got the laptop out ... and I've pretty much been working on it ever since."