We know sitting all day in an office chair is killing us, and there's no shortage of stories in the news telling us so. And while you should limit sitting, standing for long periods isn't that much better, according to a new study.

The research, published in Human Factors, the Journal of the Human Factors and Ergonomics Society, found that workers who stood all day experienced significant muscle fatigue, regardless of age and gender.

Prolonged standing can lead to leg cramps, backaches, varicose veins and other ailments that can affect job performance. And that sustained muscle fatigue causes more serious joint problems over time, according to the study.

"So there are a lot of effects that are quite nasty," said Bernard Martin, one of three researchers involved with the study and an associate professor at the University of Michigan's College of Engineering.

The researchers looked at two groups of participants — ages 21 to 30 and 55 to 65 who simulated standing work for five-hour periods, including brief seated rest breaks and a 30-minute lunch. Through participants' own self-reporting and electronic muscle stimulation, researchers found the participants all experienced some amount of muscle fatigue.

The electronic test was a more accurate measure of workers' pain than workers' own subjective assessments, since they may self-report differently, Martin said. He also noted that sometimes workers may not even realize they feel fatigue at the time.

About half of all employees worldwide are required to stand for more than 75 percent of the workday — such as restaurant, retail, factory or healthcare workers, to name a few.

"There are a lot of complaints among these workers of back pain and also some complaints of varicose veins associated with standing work," Martin said. "We thought we have to investigate further, deeper, to be able to quantify the long lasting effects of fatigue."

Martin says the topic of standing in the workplace hasn't been studied thoroughly enough to provide any recommendations to employers, but he hopes continuing research will find the answer.

"We don't think that recommending a reduction of the work time is a particular solution," he said. "We are trying to find better alternatives to that."

However, Martin doesn't have any objections to the increasingly popular standing desks that have been showing up in offices these days. In fact, he encourages sedentary workers to use them for at least some of the workday — because we can't discount the dangers of sitting all day, either.

After all, a study published in January in the Annals of Internal Medicine showed sedentary behavior can lead to cardiovascular disease, Type 2 diabetes and cancer, even among people who exercise. And a separate study earlier this month in Cancer Epidemiology, Biomarkers and Prevention found women who sit too much during their leisure time have an increased risk of several types of cancer.

The real consensus, Martin says, is that our bodies just weren't made for work that requires sitting or standing all day — it strains our muscle system in a way it wasn't designed for. For now, he says the best solution is combination of sitting and standing if possible.

"But some workplaces may not allow for the alternation of sitting and standing," he said. "We are looking at alternatives at what would be the best cycle of standing and sitting."