This is the time when many of us pledge to do better in the new year. Among the top resolutions routinely are to lose weight and get more exercise.

Before joining the health club or buying fitness equipment, you may want to read a provocative new book, Exercise Will Hurt You: Concussion, Traumatic Brain Injury, and How the Dangers of Sports and Exercise Can Affect Your Health.

The author is Steven Barrer, director of the Neurosciences Institute and former chief of the division of neurosurgery at Abington Memorial Hospital. As such, he is certainly qualified to speak about the damaging impact on the brain of boxing, football, and ice hockey. But Barrer goes further, acquainting readers with the potential hazards of such sports and modes of exercise as running, cycling, yoga, the marathon, and CrossFit.

No one can accuse Barrer of hiding his biases. In the introduction, he declares: "I hate to exercise." And a sentence later: "I am physically lazy." That puts Barrer in the company of millions of his fellow Americans, including many medical colleagues who, he writes, view exercise as a "necessary evil."

The aspect of Barrer's book that hooked me was the declarative title. He does not say exercise may hurt you. He says it will hurt you. At first, I thought such a claim was too broad and sweeping. On reflection, I realized he is right. Every sport or physical activity I've engaged in over the last 50 years - running, wrestling, weightlifting, squash, tennis, cycling, etc. - has injured me at one time or another.

Barrer recounts his own battle scars: a broken hand, collarbone, ribs, and fingers and assorted strains, sprains, contusions, and lacerations.

"I posit that exercise can be bad for you in several ways," he writes. "Injuries can result from routine participation. . . . And there are hidden dangers that lie in the cumulative effect of even the seemingly most trivial of injuries or just the overuse of our joints and muscles in the absence of injury."

He elaborates: "We wear out. And the older we get, the more we wear. We just can't do at 45 what came easily at 25. And even those under 25 often overdo it."

For you macho CrossFit fans and lactic-acid junkies, Barrer is especially contemptuous of the mantra "no pain, no gain" - "unquestionably the stupidest thing I have ever heard." Pain is the body's signal to stop!

When I spoke to Barrer, he told me his book began as an essay meant to justify the fact that he's a "lazy exerciser." He soon realized he had much more to say, and in the end, he produced what he hopes is a convincing call for common sense and moderation and a protest against "the cult of exercise" and what he calls "the sports-industrial complex."

Indeed, according to Barrer, we Americans spend $180 billion a year on dietary products, nutritional supplements, exercise equipment, and gym memberships.

The result?

"I've seen a career's worth of back pain, neck pain, arm and leg pain, altered gaits and numb hands and feet that are the culmination of a lifetime's wear and tear on the human body," Barrer writes. "Many patients come to me when a sport or exercise can no longer be performed without causing pain, and they want the problem fixed."

As a neurosurgeon, Barrer makes every effort to seek the informed consent of his patients, to make sure they realize the potential risks and downsides of a procedure. His book, he says, is an attempt to do the same for sports and exercise, to "educate people about things they're not aware of or don't think about."

He supports his arguments with medical knowledge, scientific studies, and his own experience, and he's not averse to leavening his sermon with humor.

As a longtime runner, I knew about the toll it takes, the pounding on the joints (including the spine), and how extreme exertion can thicken the heart muscle, leading to potential arrhythmias. But I was surprised to learn that yoga, supposedly a healing practice, can also damage the body. Certain postures can injure the back and neck, compress nerves, deprive the brain of oxygen, and, in rare cases, cause strokes and arterial tearing or splitting.

It should be emphasized that Barrer is not against exercise and leading an active life.

"Nowhere do I say that exercise isn't good for you," he says. "I'm not saying you should hang up your running shoes and we should all become couch potatoes."

In fact, Barrer, 64, exercises regularly on an indoor rowing machine and a stationary recumbent bike, and he proudly walks 2.5 to four miles in the course of his daily hospital duties.

"I am of the belief," he writes, "that there is a proper medium between being completely sedentary and fanatically active."

"Well Being" appears every other week, alternating with Sandy Bauers' "GreenSpace" column. Contact Art Carey at art.carey@gmail.com. Read his recent columns at www.philly.com/wellbeing.