You shouldn’t drink water during yoga class.
Your yoga instructor may argue that reaching for your water bottle in the middle of class breaks your concentration—but so does the woozy, lightheaded feeling that can result from dehydration. As for the claim that sipping water between asanas affects your subtle energies
and cools your system in a way that negatively affects your physical practice: This has yet to be proven by science. A few sips—not guzzles—during your practice won't make it more difficult to perform poses, says Matthews (who, as a registered yoga instructor, teaches classes with the yoga certification program at Miracosta College) and can be especially important during Bikram or other challenging classes in which you're sweating profusely. Your instructor may want you to learn how to manage mild discomfort, but that doesn't mean she wants you to suffer (and if it does, you might want to find another yogi).
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