They have found that women who look at their reflections during a workout feel more tired and less relaxed than those whose eyes are trained elsewhere.

They are also much more likely to have negative thoughts about themselves.

These women were not regular gym goers. They were asked to cycle a stationary bike at a moderate pace for 20 minutes.

Tired and exhausted

The researchers found that women who cycled in front of a mirror felt worse after their workout.
They felt less energized, less relaxed and less upbeat compared to those who trained without having to watch their own reflections.

They were also more likely to say they felt exhausted after the 20-minute routine.
The researchers said the findings could explain why some women stop going to the gym.

"Certainly, if a women leaves the gym feeling even worse than when she arrived, she will not be particularly motivated to continue exercising in the future," said Dr Martin Ginis.

Many gyms have wall to wall mirrors.
In some cases, this is to make the gym look bigger but in others they are designed to help people to exercise.

For instance, people who use free weights are advised to lift them in front of mirrors so that they can check their technique.

Nick Hudson of Holmes Place, one of the UK's biggest gym companies, said some people can benefit from training in front of a mirror.

"We haven't been all that big on having mirrors in the cardiovascular areas of our gyms.
"In most cases, we have big televisions and we rather people concentrate on them.

"However, we do have large mirrors in our weights areas and we do advise people to train in front of them."
But speaking to BBC News Online he added: "Most people look pretty terrible when they start exercising.

"People should not let mirrors or how they look get in the way of the long term benefits of exercising."