Britain's chief medical officer recommends that adults should achieve at least 30 minutes of moderate activity five or more days per week. No specifications are made for particular age groups, but the advice is to accumulate exercise as part of your daily routine until you have amassed the target amount. No need to pound it out at the gym for half an hour a day, just get moving more.
Don't restrict your exercise to the weekends, advises Louise Sutton, senior lecturer in health and exercise science at Leeds Metropolitan University. "Squeezing your physical activity into two days puts more intense strain on your body and doesn't increase your fitness levels as effectively as more consistent activity over the week," she says.
Get some instruction: Sutton suggests either joining a gym or a running/swimming/walking club where you will get expert tips and coaching advice to ease you back into action. Your local authority will have details of all leisure and fitness clubs and societies.
Balance your activities. Try to include elements of aerobic exercise (swimming, walking, cycling), flexibility (yoga, below, or Pilates) and resistance work, which is important for strengthening bones and preventing osteoporosis as you get older (try weight training).
Stick to the 10% rule, which means don't increase your usual activity by more than 10% at a time. "If you normally walk two miles, don't try jumping to 12 miles," says exercise physiologist Kate Owen of the Olympic Medical Centre. "Build up your fitness gradually, especially when weight training."
Remember to rest. Allow time for your body to recover and adapt to activity, especially if trying something new, says Owen. Active rest, like a gentle walk, will help you avoid overtraining and injury.
Always warm up until you break into a light sweat, and stretch before any physical activity. Claire Small, a physiotherapist for the Chartered Society of Physiotherapists says that muscle loss usually begins in the mid-40s (earlier if you're inactive) and it may drop by as much as 10% after the age of 50. "As you get older, you also lose water content from all the body's structures, including cartilage that protects joints," she says. "Tissues become weaker and less compliant, all of which means injuries happen more easily." In short: the older you are, the stiffer your body and the more important it is that you are well-prepared for working out.
Classes at gyms or leisure centres are a great way to ensure you don't overdo things early on. "Because they are a defined length of time, there is no chance of you pushing on when you should stop," Sutton says. "And there is the advantage of an instructor keeping watch over you."
With sports, take lessons every so often, even if you've been playing for a long time - a rusty technique could predispose you to injury. Use good equipment, especially the shoes appropriate for your sport, and replace them as soon as they start to look worn.
Last year, the American Academy of Orthopaedic Surgeons (AAOS) and the National Athletic Trainers' Association launched a campaign aimed at reducing the number of workout-related injuries among the baby-boomer generation (people born between 1946 and 1964) - a phenomenon they term "boomeritis". Figures from the US Consumer Product Safety Commission reveal that sports injuries among the 50-plus age group have risen by 33% in the past 15 years, an increase that experts suggest is mirrored in the UK.
Ironically, if you were seriously sporty in your youth and did a lot of intense training, you may be more prone to overuse injuries later in life. "The most common types of injuries that occur to baby boomers are often the result of years of overuse to the musculoskeletal system: old injuries that occur again; the normal 'wear and tear' of tendons and joints; and muscle-loss associated with ageing," says Dr Nicholas DiNubile, an orthopaedic surgeon and fellow of the AAOS. "Because of age-related changes, boomers' bodies are just more vulnerable." If you have or have had a sports injury, consult a physiotherapist to develop a fitness routine suited to your needs to help avoid recurring problems.
Don't forget your age. "The important thing is to listen to your body," says Claire Small. "Don't just dive in expecting to achieve what you did 10-15 years ago as you may find that you are not as flexible, as you once were or that you cannot tolerate the same types of activities that you did before. You may need to modify your fitness programme to meet your current needs and ability."