Why this is necessary may not be clear to you, but fortunately she lays it out for us:
Your yoga teacher may bow to her class saying, “Namaste” (“I bow to the divine in you.”). Postures have names such as Savasana (the Corpse Pose) and Bhujangasana (the Cobra or Snake Pose). References are made to chakras or “power centers” in the body, such as the “third eye.” The relaxation and visualization session at the end of yoga classes is skillfully designed to “empty the mind” and can open one up to unwholesome spiritual influences. As Christians, we are instructed to “be transformed by the renewing of your mind” (Romans 12:2). Yoga’s breathing techniques (pranayama) may seem stress-relieving, yet they can be an open door to psychic influences, as is the customary relaxation period at the end of a yoga session. Before becoming a Christian, I remember numerous instances of “traveling outside my body” during yoga relaxation periods. I wonder who – or what – checked in when I checked out? (Note: While Christians cannot be “possessed” since the Holy Spirit resides in your re-created human spirit, one may be “oppressed” by demonic influences.)
Of course, this isn’t just quasireligious frippery; it’s quasireligious frippery from someone with an agenda. The author is the founder of PraiseMoves, and will happily sell you books, tapes, etc., so you can free yourself from the spiritual dangers of Yoga. And put money in her pocket.