Not all of us can bend it like Beckham, especially if we have a sedentary lifestyle or want to be more physically active after laying off exercising for some time.

So start up slowly.

Before you begin an exercise regimen or pick up a strenuous sport, you need to keep two things in mind, said Dr Leslie Lam, a cardiologist at the Cardiac Centre.

"It is important to find out if you have any existing heart problem. Also do not exceed 85 per cent of your maximum heart rate while exercising," he said.

An example of a heart problem would be chronic heart disease, which is characterised by blocked arteries.

There is a formula to determine your = maximum heart rate: 220 minus your age = maximum heart rate. A 40 year old should have a maximum heart rate of 180 beats per minute.

Most exercise machines have a heart-rate monitor or you can count your pulse at the carotid artery located at your neck.

Dr Lam said that if people get a check-up and monitor their heart rate, they need not fear a cardiac arrest if they start exercising again. However, there are other ailments that kick in when one starts an exercise regimen like muscle soreness.

"Muscle soreness is so common and temporary that most people do not see a doctor," said Dr Jason Chia, a consultant sports physician at the Singapore Sports Medicine Centre. However, a person should see a doctor if the muscles soreness does not go away after 72 hours. Muscle soreness is usually the result of starting on an unaccustomed exercise too vigorously.

Another common problem that people might experience is knee pain.

Dr Chia said that knee pain varies with different age groups. Runner's knee is more common among younger people as they run and take part in sports more frequently, while degenerative knee pain can be associated with bone mass loss and tends to afflict older people.

He said one way to prevent these ailments is to train or exercise progressively and to ensure that you have adequate recovery after that.

Warming up exercises are necessary because they can prevent muscle soreness and joint pains. "Warming up prepares the body for movement by activating the body's muscles; it gets the heart ready for exercise too," said Mr Jonathan Woon, 29, a freelance personal fitness trainer.

Dr Chia also recommends that people consult a doctor before starting to exercise again after they have laid off physical activity for more than six months.

A consultation session will help identify undiagnosed diseases and control previously diagnosed illnesses. The doctor may also recommend suitable exercises.

"Start with basic conditioning exercises like brisk walking to build up fitness and continue for about three to four months before starting on more demanding sports like soccer," said Dr Chia.

However, there is no one-size-fits-all programme. "Exercise has to be individualised as we differ in our health and fitness levels," he added.

Older people, for instance, have a greater chance of developing diseases like hypertension and diabetes. There are also physiological changes like a decrease in muscle mass and flexibility," said Dr Chia.

Thus, individuals with osteoarthritis of the knee may be better suited for lower impact exercises like swimming and cycling rather than running.

Diabetics - with decreased sensitivity in their feet due to low blood circulation - may not be suited for running Diabetes affects the nerves which may result in decreased sensation in the feet.

In a person with no other medical problems, the slightest discomfort or abrasion, for example, from a poor fitting
pair of shoes or unaccustomed exercise, will signal to the person to take corrective measure.

However, a diabetic who does not feel the discomfort will miss detecting any foot injury and this can result in ulcers which may lead to complications if they do not heal well. This is why diabetics have to pay attention to foot care and try not to choose exercises that are more likely to result in foot injuries.

Pregnant women who want to start exercising have to proceed with caution, said Ms Chong Wan Kit, the managing director of Contours Express, a women's fitness centre. She said that exercise should be done in
moderation and pregnant women should avoid activities involving the back or high impact movements.

According to Dr Chia, during the third trimester, women should avoid back exercises as it can compress a major vein in that position which would decrease the flow of blood to the uterus and kidneys, thus reducing the amount of oxygenated air for both mother and child.

A pregnant woman's joints become looser as her body prepares for birth and high impact movement may strain her joints and make her susceptible to injury, he added.

Dr Chia said the full benefit of exercise requires time. "Abrupt increases in exercise lead to a breakdown of the body that can result in muscle soreness, injuries or tiredness."