San Francisco ? For some Americans, Labor Day isn’t so much about relaxing from hard work as it is about laboring – at least a little – to keep up with that hard work, according to a new poll.

Forty-two percent of U.S. workers said they’ll be doing some type of work on Monday, ranging from the cursory – checking e-mail or voice mail – up to traveling for work or going into the office, according to a survey of 1,169 U.S. workers by Development Dimensions International, a human-resources consulting firm.

Much of the work is likely to be of short duration and from the comfort of home: Twenty-eight percent will check e-mail or voice mail, 14 percent will catch up on work-related reading and 11 percent will sort through mail.

But 18 percent said they’d be heading into the office, and 3 percent said they’d be traveling for work.

“Americans are working harder than ever, even to the point where they can’t seem to enjoy an eight-hour holiday,” said Rich Wellins, senior vice president at DDI, in Pittsburgh.

“Some of those people may be in retail and have to work, but (for) a lot of them it’s to stay connected,” he said.

“They may have their grilling spatula in one hand and their BlackBerry in the other. They’re going to be doing e-mail, catching up on paperwork, checking voice mail,” he said.

Still, more than half of those polled – 58 percent – plan to do no work whatsoever this holiday.

And most of those who plan to work are doing so of their own volition, not because of pressure from the boss: Seventy-nine percent of those polled said they’re not pressured by anyone to do the work.

Then again, the boss might not be exerting pressure directly, but the dictates of the job often require extra hours, according to a separate DDI survey of about 4,500 managers worldwide.

For some of those managers, company restructurings and job redesigns are leading to the feeling of overwhelming workloads.

In the global study, managers worked an average of 51 hours per week, and almost one-third of the U.S. managers said they don’t have a good balance between work and life.

Of those, 72 percent said the amount of work they’re expected to handle is the main reason, while just 22 percent of the overwhelmed managers said their manager or supervisor expected them to work that hard.

But another major driver of working around the clock “is a desire for achievement,” Wellins said. It’s “the good old American work ethic, and the desire for ambition, the desire to get ahead.”

Sixty-seven percent of the overwhelmed managers said an “internal drive for achievement” is the factor, and 49 percent said their own ambition to succeed or promote their career is leading to them work too hard.

Meanwhile, a separate survey finds satisfaction with work-life balance has a lot to do with how much money you earn: Just 28 percent of workers earning $20,000 to $40,000 said they’re very satisfied with work-life balance compared with 46 percent of those earning $100,000 or more, according to a survey of 1,891 U.S. workers by Hudson, a global staffing and consulting firm.

Still, American workers appear to be a relatively happy lot: Seventy percent of the workers overall said they had fun at work, according to the Hudson survey.

Another reason American employees are more likely to work on holidays: Technology has made staying connected that much easier.

“If today we didn’t have work e-mail and voice mail,” Wellins said, “I don’t think people would work on Labor Day.”