Do you need to see a doctor before starting your exercise program?

You don't need a doctor to tell you that exercise is essential for a healthy life. But if you don't already exercise, your doctor may need to advise you if it's safe to start.

Most people can safely take up walking. But it's best to check with your doctor before starting if:

• you are extremely unsteady on your feet

• you have dizzy spells or take medicine that makes you feel dizzy or drowsy

• you have a chronic or unstable health condition, such as heart disease (or several risk factors for heart disease), asthma or another respiratory ailment, high blood pressure, osteoporosis, or diabetes.

You may want to check out a helpful tool called the Physical Activity Readiness Questionnaire (PAR-Q). It was developed by the Canadian Society for Exercise Physiology to help people decide whether to talk to a doctor before embarking on or ramping up any exercise program. You can find it at /PARQ.

Several different specialists can help you build an exercise or tailor one to suit your needs. They include:

■ Physiatrists, also known as rehabilitation physicians, are board-certified medical doctors who specialize in treating nerve, muscle, and bone conditions that affect movement. Stroke, back problems, Parkinson's disease, neuropathy, and debilitating arthritis or obesity are a few examples. A physiatrist can tailor exercises to enhance recovery after surgery or an injury, or work with limitations posed by pain or problems affecting movement. He or she can also tell you whether certain types of exercise will be helpful or harmful given your specific health history.

■ Physical therapists help restore abilities to people with health problems or injuries affecting muscles, bones, or nerves. Their expertise can be valuable if you have suffered a lingering sprain or are recovering from a stroke or heart attack. Some specialize in geriatrics, orthopedics, cardiopulmonary rehabilitation, or other areas. After having received a bachelor's degree, physical therapists must graduate from an accredited physical therapy program. Most of these programs offer doctoral degrees. Additionally, they must pass a national exam given by the Federation of State Boards of Physical Therapy and be licensed by their state. Those who specialize complete advanced training and additional national exams to become board certified.

■ Physical therapy assistants provide physical therapy services under the supervision of a physical therapist. They must complete a two-year associate's degree, pass a national exam, and, in most states, be licensed.

■ Personal trainers are fitness specialists who can help ensure that you're doing exercises properly. While encouraging and motivating you, they can teach new skills, fine-tune your form, change up routines to beat boredom, and safely push you to the next level. No nationwide licensing requirements exist for personal trainers, although standards for the accrediting fitness organizations that train them have been set by the National Commission for Certifying Agencies. Two well-respected organizations that offer programs of study for personal trainers are the American College of Sports Medicine (ACSM) and the American Council on Exercise (ACE). Others include the National Council on Strength and Fitness (NCSF), the National Strength and Conditioning Association (NSCA), and the National Academy of Sports Medicine (NASM). All fitness organizations have different requirements for training and expertise. Some trainers specialize in working with particular populations—for example, older adults or athletes—and may have taken courses and possibly certifying exams in these areas.