This concern is accurate and valid. Unfortunately, the trend will continue to grow for at least these two reasons.
First, the yoga teacher training is highly deficient. Most of them do not include in depth training in philosophy, meditation, pranayma or yoga history and evolution. As a result, teachers emerge who are primarily engaged in body activity not different from any other group fitness class. This weak training also produces instructors who are offering Beer Yoga, Wine Yoga, Rock and Roll Yoga, Naked Yoga, Cat Yoga, Goat yoga, Mariujana Yoga, etc.
Secondly, yoga studio operators are making classes far too short. Many classes are 45 - 60 minutes. Not good! Not enough time for meditation, breathing, savasana. When yoga first began appearing in American communities most classes were 2 hours - 120 minutes. Pause and think how much a teacher could include. Little by little, that time frame eroded: 90 minutes, 75 minutes, 60 minutes, 45 minutes. Some studios even offer a yoga "quickie" - 30 minutes over the lunch time.
This pattern won't change until yogis and yoginis begin supporting studios and teachers who are offering traditional Yoga (upper case). This means finding properly trained instructors who are offering classes which allow time to include the full spectrum of Yoga to heal body, mind and spirit.
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