Dear Doctor: My company provides perks for involvement in its wellness program, and I’ve decided to start biking the 4 miles (with a few hills!) to work. Do you think it’s a good choice? Any advice for getting started?

Dear Reader: First, congratulations for making this positive change in your life. Cycling is a terrific activity with multiple health benefits. Exercise, in general, has been shown to help boost energy; improve mood; reduce the risk of a range of diseases, including heart disease and certain cancers; maintain a healthy weight; add to strength, agility and flexibility; and aid in sleep.

As you cycle the 4 miles to and from work, you’ll use an impressive range of muscle groups. These include the hamstrings and quadriceps, which are the two major muscles in the legs; the calf muscles; the gluteals, which are the trio of muscles that make up the buttocks; the core muscles of the abdomen; and to a lesser degree, the muscles of the upper body. Conquering those hills will get your heart and lungs working and help build strength, stamina and endurance.

Cycling is an excellent resistance activity, which means it’s good for bones and bone density. It’s also a low-impact activity, so it’s kind to the joints. And the hundreds of tiny decisions needed to navigate a route and negotiate traffic help keep you mentally sharp. By the time you wheel into work after 30 to 45 minutes on the bike, you’ll have a nice endorphin glow with which to start your day.

The two main things to consider are conditioning and safety. If you haven’t been cycling on a regular basis, start by making sure your bike fits you properly and is in good repair. Your local bike shop can help you with that. Start training with short rides, gradually building up until you’re comfortable with your daily commute. The goal is to improve physical conditioning and also to become comfortable on the bike and out on the roads. Age plays a role as well. Once we hit our 40s, our muscles don’t perform at the same level as in our younger days. For older riders, this means more time to build strength, and longer to recover.

The main risks of cycling come from run-ins with motor vehicles, so you want to focus on safety. Always obey the rules of the road; for instance, be sure to ride with traffic, not against, and signal your turns. A common refrain from drivers is that they didn’t see the cyclist until it was too late. So make yourself as visible as possible with bright colors and reflective gear. In low light or darkness, make yourself known with reflectors, a white front light and red rear light on your bike, and again, reflective gear. And always -- this is non-negotiable no matter how short a distance you plan to ride -- wear a good helmet. It can save your life.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: I’m old enough to remember the shock over actress Farrah Fawcett’s anal cancer diagnosis, which was not a disease you heard much about. Now I’m reading that this type of cancer is relatively common. Isn’t there some kind of screening test?

Dear Reader: It’s true that Farrah Fawcett made international news when she went public with her diagnosis of anal cancer in 2006. Due to taboos associated with its location in the body, anal cancer was seldom discussed. The actress made a point of publicly sharing her medical journey until her death three years later, and she was applauded for helping to ease the stigma associated with the disease.

Now, with the release of findings from a new study, anal cancer is in the spotlight once again. According to the study, which looked at data collected by U.S. cancer registries between 2001 and 2015, the incidence of the most common type of anal cancer rose 2.7% each year for the last 15 years. The researchers said this annual increase makes anal cancer one of the fastest-growing cancer diagnoses in the U.S., particularly among young black men and older women. The reason for this increase is not yet clear.

The public silence around anal cancer means that most people know very little about the disease. It’s a relatively rare form of cancer, with about 8,300 new cases diagnosed each year. The disease is about twice as common in women as in men, and it occurs most often in people over age 50. Many are surprised to learn that the majority of cases -- more than 90% -- are caused by the human papilloma virus, or HPV. This is the same virus that we now know causes most cervical cancers, as well as many cancers of the penis, vagina and vulva. However, it is important to note that only a small fraction of those infected with HPV go on to develop cancer -- in fact, there are more than 100 strains of the virus, but many are considered “low-risk.”

Anal cancer occurs when abnormal cells begin to grow in the anal canal, the final segment of the large intestine. Symptoms of anal cancer include bleeding, stool mixed with visible blood, pain, the presence of a mass or growth, and more rarely, persistent itching. Several of these symptoms match symptoms of hemorrhoids. Hemorrhoids can usually be diagnosed with a visual and rectal exam. Anal cancer is diagnosed via a biopsy. In addition to age, race, gender and infection with HPV, risk factors for anal cancer include a history of smoking, anal sex with younger male partners, chronic inflammation and suppressed immunity due to disease or medical treatment.

Although there are no screening guidelines for anal cancer at this time, individuals who are at risk can talk to their doctors about tests or procedures. These include rectal exams and anal Pap tests. The HPV vaccine, which is recommended for both female and male adolescents, may also be helpful for adults in certain cases.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: I just turned 65, and my doctor wants me to have a bone density test. What is it, and how does it work?

Dear Reader: A bone mineral density test, or BMD, measures the strength of one’s bones. It’s an important diagnostic tool for osteoporosis, a progressive disease in which bones become brittle and fragile and can easily break.

Although our bones appear hard and static, they are made up of living tissue. The honeycombed inner framework of a bone is composed of collagen, which is a protein. A mineral known as calcium phosphate provides strength and solidity. Together, these two substances create a strong and flexible structure that successfully withstands stress.

Our skeletons have a dynamic life cycle in which old bone is continuously removed, while at the same time new bone is added. In children and teens, the addition part of the cycle outpaces removal, allowing the skeletal bones to grow in both strength and density. This cycle peaks sometime in our late 20s, at which point bone reabsorption gradually begins to overtake bone formation. Certain hormonal changes that occur in women during menopause further accelerate that imbalance. The result is that old bone may be removed too quickly, new bone may be added too slowly, or both. Over time, the honeycomb framework within the bone grows increasingly porous, while the exterior structure becomes thinner.

All of this leads us back to the scan your doctor has recommended. Known as a DXA test -- that’s short for dual-energy X-ray absorptiometry -- it’s essentially the same procedure and technology used in a standard X-ray. A machine delivers low-dose X-rays, which measure the amount of calcium and other bone minerals present in a segment of bone. The proportion of bone minerals to soft tissue reveals bone density.

The DXA test, which is most often used to measure bone density at the hip and the lumbar spine, is used to diagnose osteoporosis. It can also help assess risk of future fractures, and to detect whether a treatment for osteoporosis is working. The test, which is as quick and painless as an X-ray, is performed on an outpatient basis. It takes from 15 to 30 minutes to complete, depending on the part of the body being scanned. The results of the test, known as a T score, are presented as a comparison between your own bone density and that of a young adult at the peak of bone formation. A second measurement, known as a Z score, compares your bone density to people your own age, size and gender.

The BMD test is usually recommended for women when they turn 65. It may be recommended earlier than that if a woman has rheumatoid arthritis, low body weight or low vitamin D levels; has used a corticosteroid for three or more months; has a family history of osteoporosis; has experienced bone breaks resulting from a minor accident; has lost height; or is a heavy smoker or drinker. Depending on the results of the initial test, a followup test may be needed in one or two years.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)