For the past 11 years, North Andover resident Tom LaChance has put his back through the ringer.

He owns and operates his own FedEx Ground truck — day in, day out. A prerequisite of the job is to be able to lift a 150-pound package, and that ability gets tested regularly.

"You really do get those 100-pound, 140-pound packages," LaChance, 58, said. "I usually deliver between 250 and 340 packages a day. This is definitely a physically demanding job. You're twisting and bending and placing a lot of weight on your back."

LaChance's daily routine has caused him substantial physical pain, as is true for many people. Long days hunched over a desk, loading and unloading heavy boxes, even getting in and out of a chair improperly: It all adds up to 31 million Americans experiencing lower back pain at any given time — including an annual 50 percent of the country's work force, according to the American Chiropractic Association.

For most people, such issues are correctable by strengthening weak core muscles and doing daily posture exercises. But for others like LaChance, the problem is much more serious and can lead to spinal postural misalignment, which causes headaches, dizziness, pain and numbness in the limbs. It also can affect the nervous system's ability to do its job, as the spinal cord is a conduit for messages between the brain and the body, said Christopher Condon, a chiropractor at the Andover Spine Center.

"It's like if the frame of a car is out of alignment and you keep driving it; the car is going to wear out. That's what is happening to the body," Condon said.

Condon is a part of the 15 percent of chiropractors in America who specialize in spinal corrective care techniques, known as chiropractic biophysics, which restores the tissue in front or to the side of the spine. X-rays can show where the spine is curving unnaturally, as well as reveal when it has returned to the proper state. Once the passive rehabilitation process is complete, core exercises can target the surrounding muscles.

The three body regions most prone to injury are shoulders, the lower back and the knees. People who roll their shoulders forward, carry their head 3 inches in front of their body, or are knock-kneed are most likely to sustain strains and tears, be it on the job or at the gym, said Andrew Cannon, sports physical therapist at Merrimack College in North Andover and director of sports medicine at Northeast Rehabilitation Health Network in Salem, N.H.

"If you've been sitting for years in a classroom or in front of a computer, you've probably strained your body into a forward head and pelvis position," Condon said. "All of the muscle tendons and ligaments start to shorten and tighten, and pull your body into a hunched forward position. People will tell me, 'I try to sit up straight, but I can't hold it.' That's all due to the shortened connective tissue."

Unfortunately, pain is usually the last sign of spinal misalignment. Early warnings include banal symptoms, like stiffness or loss in range of motion in your neck and mid-back area, Condon said.

It was a FedEx package for the Andover Spine Center five years ago that literally transformed LaChance's quality of life.

"I was delivering a package to Dr. Condon's office and said, 'Hey, Doc, I got this problem with my leg,'" LaChance recalled. "He said it could be sciatica and gave me a few exercises. He said to try them for a few days and if the pain didn't go away, that it could be something else happening physically."

Previously a nonbeliever in chiropractic medicine, LaChance decided to return to Condon's office when the pain failed to go away. Results do vary, but LaChance said the stress and pain disappeared — not just in his leg but also his back — after his very first treatment.

Most patients require between 10 to 20 corrective care treatments and then monthly maintenance checkups. LaChance went back into the corrective cycle when he recently hurt his back. X-rays clearly showed the misalignment in his spine.

"My spine was skewing sideways; I could see how the spine was curving when he did the X-ray," LaChance said. "I realized it was because I really favor the right side of my body and I always throw boxes up on my right shoulder. I was really carrying the boxes incorrectly."

LaChance has continued with a full regimen of trigger-point therapy, which directly addresses the sensitive areas in his spine. And he also corrected the way he carries heavy loads throughout his workday. The combination is tackling the pain.

All of these treatments have cost LaChance thousands of dollars, but anything that could so drastically improve his quality of life is well worth it, he said.

"It has been a real commitment in my life. But it's turned my health right around," LaChance said. "To give your body the opportunity for health without aches and pain, that's something you can't put a price on — it really is priceless. I'd rather spend the money now for good heath. I feel like I made the right investment in life."

Reprogramming You

Your mother always told you to sit up straight, but you never thought the alternative could lead to injury. Ready to resume proper posture?

Here are a few exercises you can do to strengthen your core muscles and reprogram your posture, as recommended and demonstrated by Andrew Cannon, sports physical therapist at Merrimack College in North Andover and director of sports medicine at Northeast Rehabilitation Health Network in Salem, N.H.

r Shoulders: The No. 1 cause of shoulder injury is slumped forward shoulders and neck. Couple that posture with overhead weight lifting at the gym and you've got Shoulder Impingement Syndrome.

Rewire: When you wake up in the morning, sit at the edge of the bed and pinch your shoulders back, count "One," then relax the muscles. Throughout the day, repeat 100 times. This exercise should help you register mentally how to carry yourself all the time.

r Lower Back: Your lower back takes a beating from daily life. A long-term solution for back pain: Fitness. You simply need to integrate basic trunk strengthening into your workout routine.

Rewire: You've heard of Where's Waldo? But where's your belly? Where's your lower back? Throughout the day, consciously bring your belly button upward and inward.

r Knees: Many issues with the knee joint or knee cap often correlate with lifting or lowering more weight than you're physically comfortable doing — whether you're on the job or at the gym.

Rewire: Whenever you sit down, consciously move your butt backward before bending your knees. This will remind you that your knees shouldn't be the first thing to pop forward when lowering your center of gravity.

Basic back figures

r As much as 80 percent of our population will experience a back problem at some point.

r Half of all American workers annually report experiencing back pain.

r Back pain is one of the most frequent causes for missed work and the second most common cause for doctor's visits.

r Americans spend a minimum of $50 billion to treat back pain every year.

Source: American Chiropractic Association, amerchiro.org