Did you know the human body contains 68 joints?

That is not particularly germane to the sixth chapter of Dr. Robert Butler's book we are reading together; I mention it because it surprised me. I mean, after ankle, knee, hip and the corresponding arm joints, I'm at a loss to name any. I suppose it's all the little ones in feet and hands that add up.

This is the longest and most tutorial of the chapters in Dr. Robert Butler's The Longevity Prescription, packed with specific information on how to maintain physical functionality throughout our late years of life.

You've heard it before and the need for regular, continuing exercise in old age is obvious, as the doctor explains:

”Our muscles diminish with age, losing not only strength but actually getting smaller, with the result that our ability to do physical work decreases...

“Your maximum heart rate also declines over time...Lung capacity decreases with age, meaning less blood flow and oxygen delivery to the cells of the brain and other organs.

“As we age, our sense of balance becomes more precarious.”

The good news, says Butler is that we can, to a large degree, counteract those normal losses and significant benefit can be the result of modest exercise.

The minimum Butler prescribes for the aerobic health we need is three, 30-minute, vigorous walks per week. But for maximum benefit we should also include exercises to enhance balance, strength and flexibility.

The remarkable thing about this prescription is that the exercises are not hard, not time-consuming and don't cost money. Here are some of his recommendations:

Aerobic – for heart and lungs: In addition to walking, says Butler, you could choose jogging if you are up to it, swimming, water aerobics which is especially good for people with joint problems, bicycle riding, bowling, rowing and canoeing. Or mix them up to avoid boredom.

Strength Training – for bones and muscles: Butler says the results of these exercises are surprisingly immediate. You could try weight machines at a local gym or buy your own dumbbells or resistance bands.

Although you cannot go wrong with aerobic training, strength training is more complex, should not be done on consecutive days and as with all exercise at late age and particularly if you have been sedentary, consult your physician before beginning.

There are many good and simple instructions in this section, but proceed with caution and instruction.

Balance Training: About one-third of people 65 and older are injured in falls each year – often for no apparent medical reason. They are the leading cause of death in this age group. Our ability to balance ourselves declines with age, says Dr. Butler, due to slower processing of signals in the brain. But there are simple exercises that can help.

There is not the space in a blog post to quote the assessment test for balance, which can be done at home, but suggestions for exercises include heel-to-toe walking, one-leg stands (do it while brushing your teeth, washing dishes, waiting for the bus or subway), most kinds of dancing and tai chi.

Staying Flexible: There are many reasons our flexibility declines with age. Tendons become stiffer over the years, ligaments lose elasticity, cartilage in our joints breaks down but,

”Many studies,” writes Butler, “have shown that a sedentary lifestyle is the biggest single factor in lost flexibility.”

Aerobic, strength and balance training all help maintain flexibility, but stretching only a few minutes each day will also help to preserve range of motion, help keep joints supple and reduce the risk of injury. Several suggestions:

• Before getting out of bed, stretch every muscle from your toes upwards tensing and relaxing those muscles to get blood flowing.

• During the day, gently rotate your limbs and joints. Stay within their allotted range of motion. Pain means that's enough.

• Before a walk or other exercise, do some stretches holding a full extension for 10 or 15 seconds. No bouncing; it's an unnecessary strain.

• Yoga or Pilates is good.

• Practice good posture – it helps with back pain.

There is way too much in this chapter to cover it all in a blog post. There are good, long sections on osteoporosis, arthritis with explanations of various kinds of treatment.

Like all the literature on the importance of exercise, Dr. Butler repeats the oft-heard, “It's never too late,” and reminds us that exercise is essential to keep our minds and bodies healthy as we get older.

“Exercise plays a role in enabling our bodies to handle everyday stress. Exercise has been found to be as effective as selective serotonin receptor inhibitors (a class of prescription antidepressants) in treating depression.

“Exercise can lower cholesterol levels and, in some people, eliminate the need for cholesterol-lowering drugs. People who raise their heart rate and get the blood pumping vigorously through their bodies – and brains – have been cognitive function, too.”

Next week is all about food.

At The Elder Storytelling Place today, Marcia Mayo: Mama's Last Cat