As studies emerge classifying sitting for extended periods as bad to our health, wobbly stools and exercise balls are replacing office chairs, pedal sets are being installed under desks and everyone's talking about how to stay physically active while seated at their desk.

But what can we expect from active sitting? L.A.-based trainer and martial arts expert Philippe Til weighs in on the facts and fables.

Fact: Effective posture is the basis for active sitting, so if we start off slumped, we might not get anything out of it at all.

"Doing exercises in a chair or on an exercise ball without taking posture into account is like stacking fitness on top of dysfunction," says Til.

To get started, take what he calls the "horse ready" position. "Sit on the edge of your chair with your spine straight and your shoulders squared," he says, "And open up your thigh-to-trunk angle so that it's obtuse -- this part is very important. Your feet will be directly under your shoulders."

Fable: Active sitting is a good way to get in shape.

Hardly, according to Til, who says that it should never be considered a substitute for whole fitness.

"Active sitting is still sitting," he says. "It's not going to help you lose weight and it certainly won't increase your cardiorespiratory fitness levels. It will, however, get your blood flowing and can hinder some adverse long-term effects on the joints if done properly, starting with proper posture."   

Fact: Once good posture has been established, blood flow and oxygen intake improve.

The simple postural adjustment that Til suggests can open the airways in your lungs.

"I've had clients with frequently occurring headaches who have seen them stop once they changed their posture, which is most likely due to the increased oxygen intake and blood flow."

Fable: Active sitting will make joint pain go away.

According to Til, desk jockeys are prone to pains in certain joints. Take the knees, for example, which weaken in the absence of a load. Active sitting might reduce the pain a bit, he says, but it won't replace actual exercise. 

Fact: Extended sitting is more likely the cause of joint pain than exercise.

Indeed, says Til, when his clients complain of pain in, for exemple, the lower back, sitting is the culprit in most cases. The pain is the back's way of responding either to lack of use or poor posture, or a little of both.

He advises keeping the thigh-to-trunk angle open during the day to avoid the tightening of the hips experienced by most desk jockies. Keeping up your regular exercise program, however, is essential if one is to benefit from active sitting.

"Your joint pain will likely go away," he says, "and if it doesn't, it's best to see your doctor."

Getting started

Til suggests using a variety of tools, including barbells and exercise bands, that can add variety to your moves and perhaps even some calorie burn. If it's not possible to take equipment to work, start by using your desk, subtly placing your hands on the top and pushing down -- and the opposite -- to get in some isometric moves.

In the traditional seated position, push your heels powerfully into the ground. Shoulder rotations are important for keeping them square, says Til, and neck rotations engage the muscles in the spine.

Til has an upcoming translation of French fitness expert Georges Hébert’s "Practical Guide to Physical Education" into English. To be released in January, it the second edition of "The Natural Method Book."