Q: MY husband gave me a celebrity fitness video-tape for my birthday and it features my favourite movie star leading some of the classes. I wonder if there could be any harm in doing some of these moves. They look a little unnatural and I am a little overweight and out of shape. Dr Rose writes: You are absolutely correct in thinking that not all celebrity fitness videos are medically sound. Most celebrities are not fitness experts. However the exercises are usually designed or led by a fitness expert. The celebrity lends star quality to enhance the sales. Few fitness videos are reviewed for content or screened for their health effects or effectiveness. Therefore, one must rely on the recommendations of friends, health clubs or health magazine reviews. If you are a member of a fitness club, ask your aerobic or fitness instructor for their advice and recommendations. When purchasing one of these fitness videos, read the description to see whether the video is designed by a well-known and respected fitness expert. Good exercise videotapes list the level of strenuousness on the tape: beginner, intermediate or advanced. If an exercise movement doesn't look natural or you become dizzy, short of breath, or experience any sharp pain while exercising, stop immediately. Q: MY wife and I are in our early twenties. We really do not want to have a child for another few years. Therefore, we would like to know what is the safest birth control device on the market. We eventually want to start a family so we do not want anything that will cause any permanent problems. I have been using condoms so far but I know that they are not faultless. What are the latest developments in birth control? Dr Rose writes: Putting off having a baby until both you and your spouse are ready is a smart move. Due to your young age, there are lots of options for you. Barrier methods, such as condoms - for both males and females - cervical caps, diaphragms and sponges have few side-effects but their effectiveness varies greatly depending on the user. For example, the one-year pregnancy rates for the male condom ranges from two to 50 per cent, with the average being 12 per cent. By using spermicides with a barrier method, the effectiveness increases as does your protection against sexually transmitted diseases. Presuming your wife is a non-smoker, and doesn't have problems with high blood pressure, migraine headaches or blood clots, she would be a good candidate for hormonal therapies: either birth control pills, implants or injections. Birth control pills are the most reliable and effective methods of contraception. While most women use them without side-effects some experience headaches, weight gain, nausea, fatigue and circulatory problems. Depo Provera, an injectable birth control drug given every three months, is highly effective but has side effects including weight gain, bloating and nausea. Patients using the drug should be aware that it may take their bodies six months to one year toresume their natural ovulation cycles. The newest available form of hormonal therapy are thin flexible capsules place under a woman's skin by local anaesthetic, which release small amounts of hormones into the body and can prevent pregnancy for up to five years. Introduced in the United States in 1991, this method has been researched and tested in women in over 50 countries around the world. It can be removed when you decide to become pregnant. The most common side-effects are menstrual irregularities and spotting between periods. Three new birth control products may soon be on the market: 1. The female condom should be available in Hongkong by mid-1993. Inserted behind the pubic bone by hand, the female condom consists of a seven-inch long plastic bag with rings at each end. Onering holds the inner end of the bag around the cervix. The outer end is held in place by a larger ring. The effectiveness rate is about 85 per cent. Like the male condom, the female one protects against sexually transmitted diseases including AIDS. 2. A long-acting vaccine should be available in the next two years. It will work by making the female immune system produce antibodies that render a sperm unable to fertilise an egg. 3. A ''male pill'' may be available in the next five years. Doctors in Hongkong are trying to develop an inexpensive and effective version of the pill for Asian men, while their US counterparts are trying to develop one suitable for Caucasians. Made from testosterone, use of the pill leads to a reduction in the production of sperm. As you can see, there are many methods to choose from. Your best bet is to discuss these options with your physician, or contact your local Family Planning Association. Dr Rose Ong is a certified family physician licensed in the United States. She welcomes enquiries but cannot answer them individually. Specific questions should be addressed to your own physician. Additional enquiries: Peak Corporate Health Management, 525-6600, fax 525-8100.