Alex Hutchinson draws on the latest research to answer your fitness and workout questions in this biweekly column on the science of sport.
Can yoga elevate my level of fitness as well as my consciousness?
A few years ago, researchers at the University of Nevada, Las Vegas found that a brief yoga session allowed high-school track athletes to improve their mile run time by an average margin of one second. In comparison, they found that 20 minutes of motivational shouting ("You're the definition of speed!") improved performance by five seconds.
The point here is that it's very difficult to tease apart the mental and physical components of athletic performance.
"Yoga would say that there's really no way to affect the mind without affecting the body, and there's no way to affect the body without affecting the mind," says Timothy McCall, a San Francisco doctor and author of Yoga as Medicine.
One physical manifestation of yoga's impact is lowered levels of cortisol, a hormone associated with stress. "But it's an oversimplification to say that yoga is just about relaxation," Dr. McCall says. Many studies in recent years have demonstrated improvements in strength, flexibility and other measures such as bone density - unsurprising results, given the challenging, weight-bearing nature of some yogic poses.
Aerobic fitness, on the other hand, is a more complex topic. Fans of "power yoga" have no doubt that their vigorous routines provide a good cardiovascular workout. But a 2002 study from Northern Illinois University, published in the journal Medicine & Science in Sports & Exercise, found that subjects participating in a series of 45-minute power yoga sessions failed to consistently reach the heart-rate intensities recommended for aerobic exercises.
One problem with this study was that the subjects had no prior experience with yoga, says Karen Rzesutko, the lead author. "Our participants kept stopping the pose when it became difficult to hold."
As a personal trainer, Ms. Rzesutko incorporates yoga into the routines she provides clients, and she believes that an experienced practitioner "who is motivated enough to give 100 per cent to the practice" can reach and maintain the target heart rate.
Of course, if mind and body are the same, it's worth asking whether conventional exercise can provide the same benefits as yoga. Last May, researchers at Rutgers University presented results that compared a typical beginner-level yoga class with a typical resistance-training session using weights. Both routines lasted 50 minutes, and the subjects' levels of anxiety, tension, calmness, energy and tiredness were measured at 15-minute intervals for an hour afterward.
Both yoga and resistance training had positive effects - yoga improved scores on anxiety and calmness, while resistance training improved all variables. Interestingly, yoga's impact was most pronounced immediately afterward, then began to fade within an hour. Resistance training, in contrast, produced effects that intensified as recovery progressed, suggesting a longer-lasting result.
It's important to note that the weights session was perceived by participants to be "moderate exercise," while the yoga session was "light exercise" - a difference that could explain why weights had a bigger effect. But, lead author Joseph Pellegrino says, the details of the sessions were carefully chosen to mimic how people really do weights and yoga. Altering the sessions to get equivalent levels of difficulty would "falsely represent the exercise and the way it is actually applied in a real-world situation," he says.
Given the incredible diversity of yoga techniques, it seems likely that just about any claim made about its physical effects (levitation aside) can be achieved if you try hard enough. But balance is also a worthy yogic principle, says Dr. McCall, who hikes, bikes and dances in addition to doing yoga. Just as yoga can be great exercise, you shouldn't underestimate the psychic healing that a good run offers.
Alex Hutchinson is a former member of Canada's long-distance running team and has a PhD in physics.