A recent study explains why infrequent exercise does you more harm than good

Are you the kind of person who compensates for a month's absence from the gym by trying to fit ten workouts into one session and doing as much as you can, as hard as you can? If so, recent research suggests that a sporadic approach to exercise could be putting your health at risk.

American scientists from the William Beaumont Hospital in Royal Oak, Michigan, and Wayne State University School of Medicine in Detroit studied three million fitness club members across the US for over two years. They tracked how often they came to the gym to work out and found that out of 71 fatal heart attacks that occurred during or after a workout, almost half of these incidents affected people who exercised less than once a week on a regular basis. The authors concluded that people who only work out occasionally have a small but definite increased risk of having an exercise-related heart attack.

Now, before you cancel your own gym membership and vow never to sweat again, bear in mind that the risk is still very low at one death in 2.57 million workouts and that those who died were an average age of 52 and already had one or more risk factors or history of heart disease. "It's likely that the people who died had been exercising at an excessive intensity and may have avoided a heart attack had they been exercising less vigorously," says Dr Barry A Franklin, co-author of the study and director of cardiac rehabilitation at William Beaumont Hospital in Royal Oak, Michigan.

Nevertheless, if a strenuous exercise session can put this kind of strain on your heart, should you give up workouts altogether unless you can make them a habit? Like everything else, moderation is the answer. "If you haven't been exercising regularly, it's best to start out slowly. You can't expect to jump into a new kind of exercise head first and for your body to withstand it if you're not fit," says exercise physiologist, David Bentley, from the University of Bath. Dr Bentley likens your body to a plant - if you give it too much water at once, it will die. But if you give it a steady stream, it will grow healthily.

Dr Len Almond, exercise physiologist from the British Heart Foundation National Centre for Physical Activity and Health at Loughborough University, agrees that you're not going to see any improvements in fitness or get many health benefits if you only workout a couple of times a month. "If you're sedentary, when you start exercising, your heart and circulation adapt and your muscles learn to use the extra oxygen, helping you walk faster or further," he says. However, if you work out once or twice in a row and then stop altogether, Dr Almond reckons within three days your body's back to where it was before you started. In other words, you haven't progressed at all.

Making exercise a regular habit is more important than giving it your all during a random trip to the gym. If the reason that you're working out in fits and starts is that you often feel that you can't spare the time to travel to the gym, work out, then shower, try sticking to a lower maintenance activity like brisk walking that you can do almost anywhere without even changing clothes.

It's tempting for new exercisers to make up for lost time by giving 110% on their first exercise session. But it's crucial to take it easy. "Start off small, but think big," says Dr Almond. "Make sure you warm up and cool down. You shouldn't feel any discomfort. If your workout is too intense, you'll not only get put off, your muscles will be sore and achy because you haven't given your body time to adapt." He suggests starting with a 10-minute walk a couple of times a week, then gradually increasing the length or frequency of your workout until your body gets accustomed to it. Dr Almond recommends starting at 15 minutes, moving up to 20 minutes and finally working your way up to 40 minutes of exercise three times a week.

What if you prefer gentler exercises such as yoga but find yourself going to class only once a month? "If you haven't been to a yoga or Pilates class for a while, it's best to stick to a beginner's class and not push yourself too far," says yoga therapist, Liz Taylor, from The Yoga Therapy Centre at the Royal London Homeopathic Hospital. "Like any exercise, it takes time to retrain your muscles and loosen the joints. If you push yourself too far, too soon, warns Taylor, you're in danger of pulling a muscle because your body's not supple enough to handle the moves. Most yoga classes incorporate the warm-up into the session, but if your class is held in a cold hall or you feel the warm-up is inadequate, she suggests going for a brisk walk on the way to prepare your muscles.

"We have so many daily habits that are bad for our body - sitting in office chairs, stuck in cars, or slouching on sofas - that being active once a fortnight or once a month isn't enough to counteract the harm we do every day," she says. "That's why frequent exercise is important." She adds, however, that even people who go to yoga once a week do see improvements.

Whatever your choice of exercise, remember it isn't what you do but the way you do it and how often you do it that counts.