This means a loss of 5% of metabolic rate every ten years. By the age of 80, most women will only have around one third of the muscle mass they had when they were 40. This process is called Sarcopenia. And it isn't just age that can have this effect, under use of muscles can make the process start at a much earlier age, much like the astronauts.

Strengthening exercises can not only delay the onset of Sarcopenia, they can actually reverse the process, resulting in increased strength and a higher metabolic rate. Here are some of the other advantages of strength training:

• In a study the thighs of women who did strength training for a year were on average 73% stronger. Loss of fat meant that they were slimmer too, even with a 8% gain in muscle size;
• Muscle is active tissue, so it consumes energy, unlike fat which is inert. The more muscle you have, the more you can eat without putting on weight;
• The better your muscle to weight ratio, the lower your chance of heart disease. Even most people with cardiac problems can benefit from strength training;
• Every year after menopause, a woman loses 1 per cent of her bone density. Women who do strength training gain 1 per cent. This dramatically reduces the chance of fracture which is normally a 30% chance of a hip fracture by the time a woman reaches 70;
• Strength training lifts depression. This due to a combination of feeling better about yourself and the chemicals releases during training;
• Women in a strength training programme are 27% more active by the time they finish the programme;
• There is now some evidence that internal muscles - those that control digestion benefit from strength training;
• Your appearance will greatly improve as lean muscle replaces body fat, giving your body better definition.