Regression to the Mean

The past two semesters my graduate coursework has largely revolved around statistics. As I mentioned in a previous posting, I am not proving to be a standout statistician, though I am still picking up the essentials. Among the essential ideas of statistics is the notion of regression to the mean.

In last week's readings, the textbook cited people's heights as an example of regression to the mean. People come in many different shapes and sizes. More specifically, some people are very tall, some people are very short, though the majority are within a small band of heights around the population average. Regardless of family of origin, genetics or other variables, adult height strongly trends toward the average (mean).

I found this interesting, and not solely because I am 6'6" and more than three standard deviations away from the mean. I found it interesting that when very tall people have children, their children are rarely so tall. And after a few generations, the children of even the tallest people tend to a more average height. And the same regression to the mean holds true for very short people. When very short people have children, their children are almost always taller than their parents.  Successive generations of kids, independent of their heredity, tend toward the mean in most criteria.

Regression to the mean is found in most, if not all, natural systems... including Yoga and Pilates.

I've taught Yoga for almost thirty years, and have now taught Pilates for more than ten years. Within the arc of this career, I've seen many trends come and go. For many years I considered the various offshoots of Yoga to be borderline blasphemous, though I'm reframing that view through the lens of regression to the mean.

In the US, the corpus of fitness has stayed relatively constant. There have long been various paths to build strength, mostly involving lifting/pulling/pushing against resistance. While some minor details vary from this form to that form, the basic essence of strength training has stayed pretty constant. The mean, if you will.

Similarly, the paths to building cardiovascular fitness mostly involve activities that elevate the participant's heart rate for some length of time. As with strength training, details vary from form to form, though the basic essence of building cardiovascular fitness has stayed more or less the same. Again, the mean, if you will.

When Yoga first burst on the popular US scene a few decades ago, it was touted as being your one-stop-shopping for a strong and supple body, healthy nervous system and a calm mind. Whether or not these claims were or are true, Yoga was significantly removed from the fitness mean. If running on a treadmill and lifting weights were the average (mean) way to get fit, Yoga was the outlier among outliers.

After a few decades of operating far outside the mainstream, Yoga has seen successive generations marching progressively closer to the mean. At first these changes seemed relatively small, such as playing recorded music in classes, covering studio walls with mirrors or adding weights/resistance to class routines, though they've summed to make Yoga in 2019 a far cry from what Yoga looked like in 1979. While I used to mourn what I considered Yoga's co-opting, I am now reframing the changes in Yoga as a normal and natural occurrence. Maybe these changes are not devolution, but rather, the imprint of nature's inexorable march toward the mean? In this particular case, the mean may be more cultural than biological, though I think the same forces are afoot in both cases.

While I'm often nostalgic for the Yoga that I practiced in the cozy, stand-alone studios I loved to visit in Maui and Boulder, I'm recognizing that it's unrealistic to expect that any activity can or should remain frozen in time. And particularly, I'm recognizing that the mean is a powerful magnet that inevitably outstretches its arms and draws in all who pass by. Yoga, as it goes, now looks significantly more like fitness than it used to. And with regression to the mean as a powerful force in the natural world, it seems likely that Yoga (and Pilates) will almost inevitably trend closer to the mean in coming generations.

The evolution of the practices that I am attached to demonstrate nature's enforcement of impermanence - the often invisible force that shapes the wonder of life as we know it. And thanks to regression to the mean, I am forced to recognize the impermanent nature of the objects of my attachments.