It seems somewhat ironic, but the exercise regime often recommended by doctors and therapists as a rehabilitation tool to overcome a range of sports injuries can itself be a cause of harm.
Yoga, considered a relatively gentle means of building flexibility, muscle strength and endurance through physical poses and controlled breathing, can lead to a number of repetitive strain injuries and even osteoarthritis, doctors say.
"Most of the injuries I see are from repetitive strain," says Dr. Raza Awan, a Toronto sports medicine physician who's been practising yoga for about a decade.
The most common yoga-related injuries he sees in patients are rotator cuff tendonitis and tears; spinal disc injuries in the low back and neck; cartilage tears in the knee; hamstring strain and tears; and wrist injuries.
There are a number of reasons why yoga — in which practitioners generally perform a series of poses, called asanas — can cause injury, he says.
One is "definitely pushing too hard" to attain a specific pose, which can involve stretching the upper body into a forward or backward bend, twisting the torso, or performing an inversion, such as a handstand or headstand, balanced on the hands or forearms.
"So, for instance, people who are too flexible or people who are too tight, they're at more risk, I find," says Awan. "If you're too tight and you try to force yourself into a pose and your muscles aren't flexible, then you might strain another area to compensate."
"Or let's say that you're very flexible and you get to the end range of a pose and you don't have the muscular support to maintain the pose ... you're holding the pose without muscular endurance, you're basically holding it on your ligaments or your tendons and you strain those structures that way."
Ego also can lead to injury, he says, explaining that in yoga classes, some people push their bodies beyond their limits trying to match or outdo the person on the next mat.
Even competing with oneself — for instance, trying to get the heels flat to the floor during the "downward dog" pose, despite having tight calf muscles from sitting at the computer for hours — can lead to strains or tears, he says.
"You strain yourself because you push yourself."
Sometimes, overdoing it in yoga may exacerbate an underlying problem called femoroacetabular impingement, or FAI, in which the bones of the hip are abnormally shaped and don't move together smoothly. The hip bones grind against each other during movement, causing joint damage over time and osteoarthritis.
Dr. Chris Woollam, a Toronto sports medicine physician, says he started seeing "an inordinate number of hip problems" about two years ago, including among women aged 30 to 50 who were practising yoga.
When range of motion in their hips was tested, not only was movement limited, but "they would jump off the table because of the pain," Woollam says.
MRI scans showed the women had joint damage resulting from FAI, which can be severe enough in some cases to require hip-replacement surgery.
"So maybe these extreme ranges of motion were causing the joint to get jammed and some to wear," Woollam says of certain yoga poses. "If you start wearing a joint down, then it becomes arthritic. So you're seeing these little patches of arthritis in an otherwise normal hip that seems to be related to these extremes of motion or impingement or both."
That appears to have been the case for Cory Lund, a Toronto artist who started doing yoga about 20 years ago after he injured his back in a snowboarding accident. He found the stretching exercise helped alleviate the pain better than anything else he tried.
Over the years, he practised different kinds of yoga, most recently one called ashtanga, a more vigorous type that involves moving through a series of progressively challenging poses.
But about 18 months ago, Lund began experiencing periodic bouts of nagging hip pain. He was diagnosed with FAI in his right hip.
"It is an injury and I know that now, but it's not like there was some catastrophic moment," says Lund, who is taking a hiatus from yoga.
"My body can only do what it does and the whole point of yoga is to respect its limits. I'm not a terribly flexible person.... When I moved into the positions that are the end range of motion, it has caused damage," he says.
"Yoga isn't entirely to blame. You just have to listen to your body. When it's saying there's a pain, then you have to recognize that."
Vancouver chiropractor Robin Armstrong, who's been practising yoga since 1999, says the most common injury she sees among fellow enthusiasts are hamstring strains. Typically, they are overuse injuries and tend to occur more among experienced practitioners than beginners.
"I think it's also just repeating core movement patterns, and if you have a teacher who corrects the way you're moving, I think that can help prevent these types of injuries," says Armstrong, who also teaches anatomy and injury prevention to yoga instructors.
"I talk about where you have to use caution in certain poses and when appropriate use certain poses for certain people and when to avoid them altogether."
Some yoga teachers will encourage students to try a more challenging pose, while others may physically "adjust" a student to correct their posture and alignment. And that can take a person to a place their muscles and joints aren't ready to go.
But Armstrong says how far and how fast an individual advances in yoga is a shared responsibility between the student and the instructor.
"The teacher doesn't know what you're feeling in your body and you have to be comfortable enough knowing, 'OK, is this right for me? This might be right for the person beside me, but is this right for me at this moment?'"
"Don't get so attached to making the pretty picture with your body, you're still doing yoga even if you're not doing the full expression of the pose," she says. "And that goes back to not comparing yourself to others, because everyone comes with a different body and a different experience."
Yoga has many upsides, including sharpening mental focus, easing stress, and improving range of motion that can help avoid injuries while performing day-to-day activities or participating in sports.
"There's a lot of benefits to doing yoga for certain types of problems, but obviously any physical activity has its risks, too," says Awan, who is among those who uses yoga as a therapy for some patients and believes most yoga-related injuries are preventable.
"It's a great movement-based activity to do, but you have to try to keep safe, just like in other sports activities. Don't push your body beyond."