Target Heart Rate Is a Guide, and Not a Hard and Fast Rule for Exercise

Dear Dr. Roach: I’m 54 years old, 5 feet, 1 inch tall and weigh 110 pounds. I’m not medicated and I do go for a yearly physical with my M.D. I exercise regularly and have done so for most of my adult life. When I ride my bike outdoors, I’m usually out for a good three hours. My heart rate averages 155, at its highest 175. I’m always still able to breathe and talk, and when I rest it comes down pretty quickly. This is a lot higher than the target heart-rate zone for my age (116-149, according to an Internet search). What are your thoughts? — A.D.C.

Answer: Target heart rate is a good example of a characteristic that varies a great deal from one person to another. The ranges that are published are right for many people, but not for everybody. The formula for women is even less accurate than the one for men. It is particularly bad for athletes, who tend to have heart rates similar to those of younger women. The fact that your heart rate comes down quickly is another sign of good fitness.

The best way to find your maximum heart rate is to have a supervised maximal exercise session. However, being able to talk during exercise remains a good way to be sure you are properly regulating your exercise.

Dear Dr. Roach: I understand that THC is the active drug in marijuana. Where medical marijuana is legal, why isn’t THC extracted and prescribed?

It seems there would be more-consistent dosage, less risk of lung disease, no secondhand smoke issues and no fire risk. — T.A.

Answer: Synthetic THC has been available for years as the prescription medication dronabinol (Marinol). It is Food and Drug Administration-indicated to treat nausea associated with chemotherapy and to help people with advanced HIV gain weight, but is also used for pain, headache and other symptoms. It does indeed have the benefits you mention, but many people feel the synthetic drug does not work as well as actual marijuana, which has several types of THC, not just the delta 9 that is in Marinol. It is a class III restricted substance.

Medical opinion is divided about whether natural marijuana has any benefit over the synthetic, exactly dosed and purified pharmaceutical product. In addition to the many other active substances in natural marijuana, oral use is different from smoked, since any drug taken orally must go through the liver, which metabolizes it into yet more compounds. The American Medical Association has recommended further study before it is recommended for general use.

My limited experience is that synthetic Marinol is very effective for a subset of people.

DR. ROACH WRITES: In January I wrote about cluster headaches, and many readers took the time to write in with what had been helpful for them. Among the treatments recommended were the antidepressant Zoloft, and the anesthetic lidocaine administered in the nose. Several readers wrote in to tell me that acupuncture cured them. Mold and food sensitivities also were frequently mentioned, with an antihistamine and avoidance of offending agents being helpful. Botox, commonly used for migraine, was the key for at least one reader. Finally, several people said chiropractic manipulation cured their headaches.

It is easy to say, “If it worked for someone else, it will work for me.” However, the body is vastly complex, and it takes a great deal of judgment to know what is right for a given person. I don’t pretend to have all the answers, but I wanted to share my readers’ experiences. What is certain is that none of these treatments will work for everybody.

Many headache questions reach me on a regular basis. For a general explanation of headaches and their treatment, consider the booklet on that topic. It presents a comprehensive view. To order a copy, write: Dr. Roach -- No. 901, Box 536475, Orlando, FL 32853-6475. Enclose a check or money order (no cash) for $4.75 U.S./$6 Can. with the recipient’s printed name and address. Please allow four days for delivery.

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Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to or request an order form of available health newsletters at P.O. Box 536475, Orlando, FL 32853-6475. Health newsletters may be ordered from

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