When it comes to yoga, some like it hot. Enticed by promises of weight loss and purification, Bikram enthusiasts crowd into 104-degree-Fahrenheit rooms, which guru Bikram Choudhury calls "torture chambers." Some students get nauseated. Others pass out. Outer thigh numbness is less common, but just as dangerous as some of the other side effects.
Before You Blame Bikram
The most common form of outer thigh numbness -- meralgia paresthetica -- results from compression of the nerve that supplies sensation to your outer thigh. Pregnancy, obesity, tight clothing, diabetes and long-duration standing can trigger meralgia paresthetica. Scar tissue from past injuries might also take responsibility. Before you make assumptions, get a doctor's diagnosis of what's going on in your body. If your doctor rules out meralgia paresthetica, your outer thigh numbness might be related to Bikram yoga practice.
Inductees into the cult of Bikram are told not to drink water during the class, and to breathe through their discomfort and remain in the room, even if they feel faint or dehydrated. Those who drink this Kool-Aid often end up severely dehydrated. Dehydration causes electrolyte imbalances. Your electrolytes include minerals such as sodium, potassium, magnesium and calcium. These free ions regulate oxygen and fluid within your cells. Low calcium levels sometimes cause leg numbness, explains Sonia M. Astle, RN. General electrolyte imbalances can also trigger a syndrome called unilateral leg numbness.
Your Sartorius Takes the Heat
Your sartorius muscle sits in the front of your thigh. Originating at your hip bone, it meanders downward, crosses toward your inner thigh and meets its insertion point at your shinbone. The word sartorius stems from the Latin for “tailor.” Tailors often sat cross-legged while doing their work. External hip rotation of the sartorius muscle allows you to sit cross-legged. Extreme external rotation lets you contort your legs into a full lotus. Under normal circumstances, your hips would beg for mercy, but your muscles might surrender to the heat of the Bikram studio. That doesn't make it a good thing. Dr. Robert Gotlin, director of orthopedic and sports rehabilitation at the Beth Israel Medical Center told the "New York Times" that stretching muscles beyond 25 percent of their resting length causes muscular damage.
Sartorius Trigger Points
Trigger points are muscle knots that cause referred pain or numbness in other body parts. Sartorius might mimic the symptoms of meralgia paresthetica, explains massage therapist Scott M. Belanger. William J. Broad, author of "The Science of Yoga: Its Risks and Rewards," told the "New York Times" that Indian yogis sat cross-legged in daily life, so positions like the full lotus came naturally. Fast forward to the 21st century. We sit in chairs, with our legs in parallel alignment. The extreme external hip rotation required of many yoga postures shocks your body. Belanger explains that "contorted yoga postures" can create trigger points in your sartorius muscle, which cause outer thigh numbness.
In 1999, Lisa Mercer’s fitness, travel and skiing expertise inspired a writing career. Her books include "Open Your Heart with Winter Fitness" and "101 Women's Fitness Tips." Her articles have appeared in "Aspen Magazine," "HerSports," "32 Degrees," "Pregnancy Magazine" and "Wired." Mercer has a Bachelor of Arts in psychology from the City College of New York.