Rubbing In Sweat
From a new reader:
“I just found your blog and am enjoying perusing the posts. I practice ashtanga yoga and I’ve heard many times that it’s important to rub the sweat you produce while practicing the asanas back into your skin. The idea is that the sweat preserves your increased heat, and therefore the benefit of your practice. It’s said that if you wipe the sweat away, you actually weaken yourself in the long run, and on the other hand, if you rub the sweat back into your skin, it acts like the fountain of youth. People are adamant about this! And yet it makes no intuitive sense to me. Do you know of any medical reasons why this rubbing in of the sweat might actually work, or why it might not? I’d love to hear a scientifically based consideration of this practice.”
Some yogis today are adamant about rubbing in sweat. It’s a directive that’s been passed down orally through the ages and is in writing in the classic 15th century yoga manual, the Hatha Yoga Pradipika.
“Heat” can be interpreted as energy in yogic terms. Depleting electrolytes and fluid through sweating can result in dehydration and a a feeling of energy depletion with low stamina.
Gurus of old realized that when we sweat, we lose fluids and valuable nutrients through the skin. Conserving the fluid loss by rubbing it back into the skin rather than letting it evaporate was thought to be helpful. Remember that this was back in the days before running water flowed freely and abundantly from faucets in several rooms of a home. Those yogis were pulling up buckets from a well or carrying it from streams. It was a valuable resource that one had to work to obtain in most cases. We live in an age when clean water is readily available and we all know of the importance of staying hydrated by drinking to thirst. We also know from the science now that not much water will be absorbed across the skin surface.
The nutrients lost through sweating are mostly sodium and chloride, but also some potassium and minor amounts of calcium and magnesium. Since table salt (sodium and chloride) was in short supply in areas not near the sea, the yogis were attempting to help the body to conserve its salt.
Turns out though that you can’t really rub the lost electrolytes back into your body. Sodium and chloride are actively transported out of the body in sweat with the aid of ion gates that require energy in the form of ATP – with the point of pulling water out with them in order to cool off the body and lower the body temperature. The water on the surface evaporates and creates a cooling effect. It serves a purpose.
There’s no mechanism for electrolytes to get back into the body in such high quantities as what is lost since there are no ion gates working in this reverse order. What little gets through the skin back into the body will do so by passive mechanisms. Since ions are polar, it will be a negligible amount.
Today, table salt is plentiful (in fact overdone), and there is no real impetus to follow this directive that was written for another time. Even if we could significantly replenish electrolytes and fluids by rubbing them back into the skin, there’s no need. We have an abundant supply through food and drink, a much better way to stay fortified and energized.