You've probably heard this advice many times from doctors and fitness buffs: If you want to stay healthy, you should be doing at least 30 minutes of moderate-intensity exercise five days a week.
But if you are not sure what's meant by "moderate intensity," you're not alone.
"When we ask people to walk at a moderate intensity, not many know what that feels like and therefore are not able to do it. They either walk far too slowly or far too quickly," said Simon Marshall, an assistant professor at the school of exercise and nutritional sciences at San Diego State University.
So, in the interest of health promotion, Dr. Marshall and his research colleagues decided to develop a simple formula that most people can follow.
They recruited a group of volunteers - 58 women and 39 men - to perform treadmill tests. As the volunteers walked at various speeds, their oxygen consumption and heart rates were monitored so researchers knew when they had reached the proper pace.
Based on these observations, researchers calculated the typical adult would have to walk about 100 steps a minute - or 3,000 steps in 30 minutes - to achieve a moderate-intensity workout. "It's a brisk walk," Dr. Marshall said.
"It's as though you were late for a meeting or trying to get to the bathroom - that kind of pace. You are not running but you are certainly not strolling."
He suggests using a pedometer and wristwatch to keep track of how many steps you take during the workout.
And if you don't have time for a full 30-minute jaunt, break it up into a series of 10-minute instalments. "You can do three bouts of 10 minutes over the course of the day, and that would be equally beneficial for your health as one continuous 30-minute walk."
But the study, which was published in the American Journal of Preventive Medicine, found one big problem with using a pedometer - a lot of them are inaccurate.
Dr. Marshall recommends buying one that was made in Japan. "And it's not because we are trying to prop up the Japanese economy. It's mainly because Japan is the only country that sets an industry standard for pedometer accuracy."
NIGHT-SHIFT CANCER RISK
In a landmark ruling, 37 Danish women with breast cancer have won the right to financial compensation after claiming their disease was linked to many years of night-shift work.
The women, mainly nurses and flight attendants, were part of a group of 75 breast-cancer survivors who had sought aid from Denmark's state-run National Board of Industrial Injuries.
Of those claims, "37 were considered to be [job-related], entitling the applicants to compensation," spokeswoman Birgitte Lynhe told Agence France-Presse. The committee handling the claims concluded that no other significant factors could account for why these women developed the disease.
"Breast cancer after many years of shift work qualified for recognition as an industrial injury," the board said in a statement posted on its website.
The decision makes Denmark the first country to officially recognize shift work as a potential cause of cancer and follows a preliminary report on the subject by the International Agency for Research on Cancer. The United Nations' agency suggested that prolonged periods of shift work are probably carcinogenic to humans. Some scientists have speculated that hormonal changes caused by a disruption of the body's circadian rhythm - or internal clock - could be to blame.
Still, many experts expressed surprise by the Danish action, saying there is not enough scientific evidence to confirm a correlation between breast cancer and night-shift work.
SHINING LIGHT ON TB
Researchers think they have a bright idea for reducing the spread of tuberculosis in the overcrowded hospitals of Third World countries.
It involves the use of a special type of bulb that emits ultraviolet "C" light.
"Just by chance, UVC is very harmful to TB bugs in the air - it damages their DNA so they can't infect people," said lead researcher Rod Escombe of Imperial College London.
Each year, about nine million people are infected with TB worldwide and almost two million die from the disease. When someone with an active infection coughs, the TB-causing bacteria can be sprayed in the air in tiny droplets - and inhaled by those nearby. Infection rates are especially high in places where vulnerable people are crowded together, such as hospitals in impoverished developing countries.
Dr. Escombe and colleagues put UVC to the test in a hospital in Lima. UVC light bulbs and fans were hung from the ceiling of some rooms in which TB-infected patients were being treated. Air from a variety of hospital rooms was then diverted to cages containing guinea pigs.
The findings, published in the online journal PLoS Medicine, revealed a 70 per cent lower rate of TB infections for the animals getting the UVC-exposed air compared with those receiving untreated air.
UVC light is produced naturally by the sun, but very little of it reaches the Earth's surface because it is blocked by the atmosphere.
Direct exposure to UVC light can cause eye and skin irritation, Dr. Escombe noted. That means the bulb must be shielded.
The light is essentially directed upward and the fan helps circulates the air so the TB bugs get zapped when they drift to the ceiling.
