HOLD fire on the weight training, hop off the stair climber and postpone your next aerobics class, because oxygen, we are being told, is set to become the new staple of the gym. If the hype is to be believed, soon you may be able to create physical perfection out of thin air, by doing nothing more taxing than lying still in a purified, artificially altered atmosphere.

Exposure to thin mountain air has long been known to benefit competitors in endurance events such as cycling, running, swimming and triathlons. Now it seems there is no reason why keep-fit enthusiasts who attend a gym can't improve their fitness levels this way, too. Following a trend that started in New York, low oxygen or "hypoxic" cubicles measuring 9ft by 8ft, are becoming a familiar sight in health clubs and fitness centres around the United Kingdom.

Looking rather like a high-tech greenhouse, the room lulls the lungs into thinking they are on an Alpine peak with an oxygen content equivalent to that which would be encountered at up to 15,000ft above sea level. With the lower than usual levels of oxygen circulating in the air, the body is forced to work harder as it acclimatises - which is why regulars at Manhattan's trendy Crunch Gym have nicknamed it the "punishment chamber".

According to the manufacturer, just sitting inside will improve cardiovascular fitness. Muster the energy to do anything remotely active and you are looking at more fat and calories being gobbled up, while your average workout time will be sliced in half.

However, the latest low oxygen product to hit the UK doesn't even require you to break into a sweat. Athletes such as Mark Steinle, who represented Great Britain in the marathon at the Sydney Olympics, some premiership football clubs and Britain's triathlon squad have all invested in hypoxic tents to gain a competitive edge.All that is required is to sleep in them and breathe the thinned-out air that circulates inside. The Low Oxygen Tent is essentially a basic two-man tent with a filter to extract pre-set amounts of oxygen from the air. Because the atmosphere is adapted to avoid the drop in barometric pressure, its UK distributor, insists there is no chance of getting altitude sickness.

Neneh Cherry and Tina Turner are fans of mountain air breathing which was developed in Russia in the Sixties and involves sticking your head inside a perspex bubble filled with purified air. You will need several sessions to feel any effect at all.

Professor Tom Reilly, of Liverpool John Moores University, an expert in the study of high altitude training, says that, used correctly, the devices can indeed help people to improve their fitness levels while they sleep.

"Spending up to eight of 24 hours in one means that a person is exposed to oxygen deprivation. The tents would have to be used systematically and regularly but can help the body to use oxygen at a more efficient rate during exercise."

Professor Tom Reilly, of Liverpool John Moores University.

Low-oxygen conditions trigger the kidney into producing more of a naturally occurring hormone called erythropoietin (EPO), says Prof Reilly, and that stimulates bone marrow into producing more oxygen-carrying blood cells. The performance-enhancing effects of EPO in endurance activities are so potent that it is listed as a banned substance if taken in injectable form.

At Staffordshire University, exercise physiologist Stephen Day has been carrying out tests on elite runners to find out just how effective sleeping in a low oxygen tent can be. The initial results, he says, are promising.

"We have assessed numerous physiological parameters and found that one elite athlete's red blood cell count has increased by 10 per cent since he started sleeping in the hypoxic conditions last November. There has also been a dramatic 30 per cent rise in his aerobic capacity - that is his ability to use oxygen efficiently - which all bodes well for his running."

Staffordshire University, exercise physiologist Stephen Day.

Prof Reilly is not surprised. He says most benefits have been noted in people who sleep or live at high altitude but train at sea level. Dr Benjamin Levine and his team of sports scientists from the University of Utah, who carried out research on 39 runners, found that those who spent four weeks sleeping in an area 7,000ft above sea level performed much better than those staying at lower altitudes. Based on these findings, some of the American swimming team now live at 6,000ft in Colorado but train at sea level.

Another new development in the oxygen fitness market is space-age capsules that actually give you more oxygen than you would normally get from breathing in air. The US-designed HyperOxy Chamber, originally designed for triathletes who wanted to recover quickly from training sessions, is now on sale over here and reportedly has other health benefits.

By mimicking the air pressure you would find 10,000ft below sea level, the chamber drives oxygen into the body's tissues. Spend 45 minutes in there, says its distributor, and you will emerge revitalised and with a renewed sense of well-being. Use it regularly and circulation will improve, as will your ability to deal with stress.

Similar high oxygen or hyperbaric chambers are widely used in hospitals because they are known to help heal wounds and severe burns. There are also claims that since some viruses and bacteria thrive on low oxygen, the chambers can be beneficial in warding off conditions such as thrush. Earlier this year, a study in the New England Journal of Medicine showed that patients who underwent oxygen therapy were 70 per cent less likely to suffer infections and were sent home much sooner than those given only antibiotics.

Whether or not we are being sold a load of hot air with some of the latest products remains to be seen, but they are not short of admirers. Britney Spears, Kirstie Alley and the Beckhams are all reported to be fans of canned oxygen and for a long time the hippest hangout in Los Angeles was Woody Harrelson's oxygen bar. Experts remain divided in their opinions on the latest health fad.

"Inhaling pure oxygen gas is beneficial for people suffering from illnesses that compromise the function of lungs and the cardiovascular system. While it isn't dangerous or harmful, for the average healthy person, ingesting extra oxygen will have a greater psychological effect than anything else."

says Dr Peter Jokl, head of sports medicine at Yale University Medical School, who has done research on the subject.

There may be no harm in using tents and capsules, but one thing is likely: the cost could take your breath away.

Overall, hypoxic training has the potential to improve aerobic capacity, cardiovascular fitness, and recovery times for athletes, potentially leading to improved performance in endurance sports and other types of physical activity. However, it's important to note that the effectiveness of hypoxic training can vary depending on factors such as the duration and intensity of the training, the individual's fitness level, and the specific type of training used.

Here are some statistics related to how hypoxic training can potentially make you fit:

1. Hypoxic training involves exercising in an environment with reduced oxygen levels, such as a hypoxic chamber or at high altitude. This type of training has been shown to improve endurance and aerobic capacity by stimulating the production of red blood cells and increasing oxygen uptake efficiency in the body.
2. Research has demonstrated that hypoxic training can improve cardiovascular fitness and increase the body's ability to use oxygen during exercise. This can lead to improved performance in endurance sports such as running, cycling, and swimming.
3. A study published in the Journal of Strength and Conditioning Research found that athletes who performed high-intensity interval training (HIIT) in a hypoxic environment had greater improvements in aerobic capacity and maximal oxygen uptake than those who performed the same training in a normal oxygen environment.
4. Another study published in the European Journal of Applied Physiology found that hypoxic training can improve running performance by increasing the body's ability to use oxygen during exercise and reducing the perception of effort during high-intensity exercise.
5. Hypoxic training has also been shown to improve recovery times for athletes, potentially reducing the risk of injury and allowing for more frequent and intense training.