It was Tough Mudder that brought me back to yoga. Last October, I was trying to get back in shape to run the popular obstacle race, but after almost a year without exercising consistently, I didn't know where to start. Turns out it's hard to tell your body that you're going to cut out Hot Cheetos and try to regain definition in your abs. I decided to start small by taking a yoga class.

I had tried yoga before, but it had been a while. After doing some research, I decided to enroll in Bikram, a type of Hatha yoga that involves doing 26 different poses in a room heated to 105 degrees. Maybe, I thought, it could help me get my training started. At the very least, it sounded entertaining.

Former Indian yoga champion Bikram Choudhury developed his brand in the early 1970s after moving to California and founding his own studio. His special practice of yoga quickly became famous, as celebrities such as Madonna and Kobe Bryant took it up. By 2006, he had 1,650 studios around the world.

Increased popularity should attract increased scrutiny, but in many cases the yoga industry, and Bikram in particular, has escaped such vigilance. Instructors in classrooms around the world continue to portray yoga as a practice of whole body-mind healing without strong skepticism on the part of consumers. “If you know that a pursuit is as popular as Bikram yoga is and they give no disclaimer, would you assume it was dangerous?" asks Tali van Sunder, a writer for BeingHealthy.TV who has reported on the potential dangers of Bikram. "People just follow everyone else, especially if they want to believe what you are selling.”

This became apparent to me on my first day of yoga. As I moved into locust pose, which involves lying on your stomach with your arms underneath you, I could feel pain in my elbow as my body blocked the flow of blood in my forearm and hand. As if anticipating my question, my teacher said: “If you feel pain, it’s good. If you feel numbness in your arms, it’s your body saying ‘thank you.’” Red flags went up in my mind. It didn’t make any sense.

I felt dizzy during class, and could count my heartbeats in my throat. I had never felt so thirsty, but my teacher said that dizziness after a pose was a good thing and I should ignore it. Every time my teacher told me to "work through the pain," I wondered: How much pain is too much?

According to Keith Baar, a biology professor at the University of California-Davis and an amateur yogi, my teacher's statements about numbness being my body’s way of thanking me were an example of "yoga physiology," the myriad of physiologically incorrect proverbs spit out by yoga instructors in their classes. This is a nice way of saying that it's crap.

Even some of the more mild physiological claims made by Bikram yoga can be disproved by basic knowledge of human body systems. My teacher kept telling my class that all the sweating we were doing was helping our bodies flush out toxins. Baar said this idea was “unfounded.” Your liver and kidneys do most of the detoxification in your body, and the toxins they clean out are excreted when you use the restroom, not when you sweat.