DEAR DR. DONOHUE: I am an avid bicyclist on weekends. Would you please enlighten me as to how to prevent or minimize annoying saddle sores? – P.F.

DEAR DR. DONOHUE: I am a policeman who patrols on a bike. I have noticed numbness in my penis. Is this from riding the bike, and could worse happen? – K.L.

ANSWER: Both complaints are common woes of bicycle riders.

For K.L.: Surveys have shown that 13 percent of male bicyclists complain of penile numbness. It should not be ignored. It means there is pressure on the nerves serving the penis, and if it continues, it can lead to erectile dysfunction. Close to 20 percent of bicyclists who ride great distances – about 240 miles a week – experience such trouble unless they stop biking to give the nerves a chance to heal.

The solution to both problems can often be found in an adjustment to the bike’s seat. It might be too high, too low, too far forward, on too much of an incline or too hard.

The seat should be at such a height that there is a slight bend in the knee when that leg’s pedal is at its lowest position.

Whether to tilt the seat or have it horizontal to the ground is something that can be learned only from experimenting. Many find that a downward incline of 10 to 15 degrees for the front of the seat provides them the most comfort.

A seat without a protruding nose takes pressure off pelvic nerves and would be a good idea for K.L. A split seat – one with a gap between the right and left sides – is another idea. Both cyclists need a more forgiving seat. A wider and cushioned seat is another possible answer for both riders.

In addition to making a seat change, P.F. should invest in shorts that don’t bunch up and that have a lining that draws moisture away from the skin.

DEAR DR. DONOHUE: I am in training now to run a marathon in the spring. I have heard that taking a carb drink while running keeps the energy level up. Does it? – K.R.

ANSWER: Blood sugar and sugar stored in the muscles (glycogen) are the major fuel sources for muscles. When the body’s supply of sugar in both forms is close to the empty level, a person becomes fatigued. At this point, fat is the chief source of energy. It doesn’t, however, completely overcome fatigue that comes from carbohydrate depletion.

It has been demonstrated that long-distance runners who drink fluids with carbohydrates (sugar) in them are subjectively less tired than those who don’t drink such fluids. It is also important in long-distance running for fluids to contain sodium and potassium. The concentration of carbohydrate in replacement fluid should not exceed 8 percent. Runners in the study I mentioned drank a fluid that contained 6 percent carbohydrate along with sodium and potassium. Carbohydrate concentrations greater than 8 percent delay stomach emptying and can cause stomach cramps.

The carbohydrate-containing drink maintains blood sugar at near-normal levels. It does not, however, stop glycogen depletion from muscles.

DEAR DR. DONOHUE: I was struck with a case of dizziness that was unbelievable. I had to stay in bed for two days because I was so unsteady that I knew I would fall if I tried to walk. I am now in my second week of this, and things have improved but haven’t gone away. The doctor says I have labyrinthitis. I need information on it. When does it go away? – L.L.

ANSWER: The labyrinth is the part of the inner ear where the balance organs are located. Inflammation of the labyrinth – labyrinthitis – makes people feel like they are spinning in space. As a result, they are frequently nauseated and often vomit. They might suffer a slight hearing impairment, and their ears might ring.

Labyrinthitis is usually due to a viral infection.

Medicines can lessen labyrinthitis-induced dizziness, but they rarely completely eliminate it. Antivert is a popularly used medicine. The Transderm Scop skin patch, a seasickness treatment, is another medicine that controls dizziness.

Two days in bed for dizziness is enough. Even if people feel unsteady, they should walk with assistance. Walking helps the brain right itself when it gets confusing messages from the balance organs.

People are generally over a bout of labyrinthitis in a few weeks to a month or so. If matters do not clear up by then, the doctor can refer patients for vestibular rehabilitation. The vestibule and labyrinth are more or less synonyms. Therapists teach head and eye movements that restore inner ear function so dizziness and balance are no longer problems. For most, however, nature takes its course, usually without leaving any permanent problems.

DEAR DR. DONOHUE: I fast-walk three miles a day and also ride my bike three miles a day. I understand both are great for a cardiac workout. If I have to give one up, which should I keep? – K.K.

ANSWER: Both do provide the heart with excellent exercise. If you have to make a choice between the two, choose to keep the one you like better. They’re pretty much a tossup. A person who weighs 150 pounds burns about 6.6 calories a minute when walking at a pace of 4 miles an hour. The same person riding a bike at 11 miles an hour burns about 7 calories a minute.

I must admit that calorie estimation is a rough guess at best. Your pulse is another way of determining which is the better workout for you. Which one raises your pulse to a higher level? Choose that one if both are equally pleasing to you.

Dr. Donohue regrets that he is unable to answer individual letters, but he will incorporate them in his column whenever possible. Readers may write him or request an order form of available health newsletters at P.O. Box 536475, Orlando, FL 32853-6475.