In mice at least, physical exercise appears to boost the production of a naturally occurring brain substance that has anti-depressive effects. Exercise has long been credited with indirect effects in terms of mitigating depression. A recent study, published in the journal Nature Medicine, suggests how it may have a direct effect as well.

Laboratory mice that worked out for a week on a running-wheel exhibited altered activity in 33 genes, one of which was for a specific nerve growth factor that helps develop and maintain neurons of the hippocampus, a vital area of the brain. The hippocampus, which is integral to memory formation and retrieval, has also been associated with mood regulation and with the brain's response to antidepressant drug therapy.

SFA author Jim Evans is a 40-year veteran of the health-exercise industry and an internationally recognized senior fitness consultant. Today, Jim provides common-sense measures that can help to diminish knee pain.

DEAR JIM: I'm only 69 years old, but my knees feel like they're 169 years old! There is a persistent, almost unbearable pain, under my kneecaps -- especially when I climb stairs or try to stand up after sitting in a deep chair or couch for any length of time. I have tried ice packs, aspirin, and other home remedies, but they only work temporarily. Is there anything else that might help relieve the pain? ACHING KNEES IN KNOXVILLE

DEAR ACHING KNEES: Your condition sounds like patellofemoral pain syndrome (PFPS). A mouthful, isn't it? Actually, it is a common injury occurring around and under the kneecap, often affecting runners, hikers, cyclists, and other athletes. But it can affect inactive people, too -- particularly older adults.

Most older adults have a tendency to lean forward when they climb stairs, placing virtually all of their weight on their knees rather than allowing the larger hip and thigh muscles to absorb the stress. The smaller knee joints naturally become inflamed, often advancing into PFPS. Fitness professionals typically instruct their clients not to let their knees extend past their toes when performing knee bends. The same principle applies when climbing stairs: Don't let your knees extend beyond your toes.

Try standing more erect when you climb stairs, and push off with your instep -- not your toes. It will probably be more tiring in the beginning until the muscles of your hips and thighs become stronger from the increased work load. But it should reduce the pain within your knees, and eventually climbing stairs should become much easier for you. Hold on to the handrail for stability, but let your hips and thighs do the work.

Of course, the problem of trying to stand up after sitting on a deep couch or chair is easily remedied by not sitting on a deep couch or chair in the first place! Again, fitness professionals will tell you not to sit "below parallel." In other words, the tops of your thighs should never be lower than parallel with your knees. If the chairs in your home are too low or deep, consider having them elevated by placing carpeted platforms beneath them or adding extra cushions. Even traditional toilets can be replaced with higher, wall-mounted units to make it easier to get up and down.

Our knees are very vulnerable to injury, and sometimes making simple adjustments in our day-to-day lives can help to prevent injuries and/or relieve existing pain and discomfort. Try these suggestions -- also follow up with me (to discuss medical intervention).

Utilizing the good-posture and the good-technique approaches described above, one can enlist stairs to optimize balance training. When performing the following exercise, suggested by Daytona Beach News-Journal medical writer Paul Donohue, MD, participants should make use of the stairway's handrail as needed for support. Also, they should have someone at hand to assist, in case they become unsteady and start to fall.

To begin, stand facing the stairs. Lift your left leg, placing its foot on the bottom step. Your right foot is still on the floor. At this point, the left knee is bent. Slowly straighten the left knee until your right foot rises to the height of your left foot. However, do not place your right foot on the step. Instead, simply tap it lightly on the step, and then bend the left knee until your right foot is back on the floor again. Reverse leg positions, and repeat. Perform this exercise several times per day as well-tolerated (reducing the number of repetitions if muscle soreness develops).

Older adult fitness practitioners -- as well as exercise physiologists, gerontologists, researchers, and university students -- will be interested in Human Kinetics' impressive new book Physiology of Exercise and Healthy Aging by Albert W. Taylor, PhD, DSc, and Michael J. Johnson, PhD. In fact, although geared toward professionals, the text is sufficiently reader-friendly that well-informed laypersons with a strong interest and the habit of delving into this topic area should also find it quite navigable. The 304-page hardcover textbook, published in 2008, can be ordered through any bookstore.

Physiology of Exercise and Healthy Aging is organized to present information in terms of three major groups: average-aging individuals, the frail elderly, and master athletes. It addresses:

That last topic -- exercise benefits -- receives an especially thorough-going and highly enlightening discussion. Physiology of Exercise and Healthy Aging makes an irrefutable case for physical activity's positive contributions to longevity, to the delay of specific age-related diseases, and to the enhancement of quality of life in our aging population.

We can undergo extensive medical procedures to confirm what we already know in our hearts: that we need to perform more physical activity! Or, we can employ a much simpler method to arrive at the same conclusion, as follows:

"If your dog is fat, you're not getting enough exercise."

-- Author Unknown