I'm pedalling away on a stationary bike in an exercise studio with a difference. The air inside mimics the air you'd find at an altitude of about 3700 metres. I'm puffing more than I normally would because it is harder to get enough oxygen.
Though my lungs feel as if they are in Mexico City, I am in suburban Mosman, at Sydney Altitude Training. It is one of only a few commercial centres in Australia where you can work out in a gym where the air has a lower concentration of oxygen.
The centre is popular with travellers bound for mountain destinations such as Machu Picchu and Everest Base Camp. Training this way can help reduce symptoms of altitude sickness, including fatigue, nausea and headaches, which can take the gloss off trekking, skiing or sightseeing in scenic places.
About 65 per cent of people going to altitudes of 4000 metres or higher will have some symptoms of altitude sickness, says the exercise physiologist who runs the centre, Allan Bolton. It is impossible to eliminate the risk completely but working out in low-oxygen air beforehand can help acclimatise the body.
''Reducing the effects of altitude sickness can be the difference between having a fun trip and an OK or even miserable trip,'' Bolton says. ''It can also be the difference between getting down from a summit under your own steam rather than being carried.''
It is difficult to predict how individuals will cope with low-oxygen environments because some are more predisposed to altitude sickness than others.
''We've had elite marathon runners who don't do well at altitude and less-fit people who do fine. Being older isn't always a handicap either,'' says Bolton, who recently trained a 75-year-old for a trek to Mount Kilimanjaro. ''Younger people who are more gung-ho are more likely to get into trouble because they want to get to the top of the mountain more quickly. But an older person who's going more slowly is giving their body more time to adjust to the increasingly low levels of oxygen.''
Training in a low-oxygen environment is more than just an antidote to altitude sickness. It can also boost physical endurance and speed - which is why it is often used to give athletes an edge when competing at sea level.
But it is not just for elite athletes; the changes triggered in the body by working out at simulated altitude can help anyone improve their exercise performance or get fitter faster.
Altitude training forces the body to compensate for lower oxygen levels. It raises the heart rate to try and take in more oxygen and circulate it around the body. After a few sessions, the body learns to use oxygen more efficiently. The advantage is that when you go for a run or bike ride in normal air, more oxygen reaches your muscles, making it easier to go faster for longer.
''You also get more of a kilojoule burn - working out at altitude burns 25 per cent to 30 per cent more kilojoules compared to doing the same exercise at sea level,'' Bolton says.
How many sessions of altitude training does it take to conquer Mount Kilimanjaro, or for weekend warriors to boost their performance? To get ready for altitude, eight to 12 sessions are ideal, while about eight sessions will improve fitness. The more exposure the better. The enhanced oxygen uptake lasts about four to six weeks after training stops.
Paula Goodyer blogs at smh.com.au/chewonthis.