You are correct. It is not at all acceptable to engage in non-Christian practices such as QiGong and Nia - which includes yoga - and think we can slap the name of Jesus over them like a band aid on a sore. It doesn't work that way.
For those who are unfamiliar with these practices, Nia is described as dance cardio fitness classes which are taught by instructors who are educated in "mindful movement guidance" and somatic education. "They employ 52 basic movements and techniques that draw on a combination of Jazz, Modern and Duncan Dancestyles, Tai Chi, TaeKwonDo and Aikido; and the bodymind healing arts of Feldenkrais Method, Alexander Technique and Yoga."
QiGong is based upon a belief in an alleged universal life force energy (qi) which can be regulated through posture and in the mind through meditation and breathing techniques. As traditional Chinese practitioners explain, qigong involves a wide range of exercises and styles, such as “tuna” which emphasizes the practice of breath; “still” qigong, which stresses meditation and relaxation; “standing stance” qigong, which emphasizes the exercise of the body by relaxed and motionless standing posture; “moving” and dao-yin” qigong, which emphasizes external movement combined with internal quiet and control of the mind. “Soft qigong” refers to exercises which enhance spiritual, mental and physical health with meditation and gentle exercises while “hard qigong” refers to exercises done in martial arts that are designed to strengthen the body and protect it from injury.
There are many reasons why we should not get into the habit of using spiritual practices derived from other religions and think that if we just call them "exercises" or pray to Jesus while doing so, it's somehow okay.
First of all, the Lord tells us in Scripture that we aren't supposed to worship him the way the pagans do (see Deuteronomy 12:30-31) so if you want to worship Jesus, then do so with the methods He gave us, not those of other religions. And if you want to exercise, than use real exercise, not Hindu and Buddhist spiritual practices.
Second, it's erroneous to claim that the Church has been "Christianizing" pagan practices since the beginning of her history so it's okay to pray the Rosary while doing things like yoga. The only people who claim the Church does this are Fundamentalists, Seventh-day Adventists, Jehovah's Witnesses, Mormons, atheists, skeptics and miscellaneous Catholic bashers. Catholic Answers calls this the "pagan influence fallacy" - a mistaken notion promulgated by anti-Catholics that falls apart under "more mature scholarship."
All Saints Day is one example. Begun in the 4th century, this feast was established by the early Christians to commemorate the martyrs who gave their lives for the faith during those first bloody centuries of Church history. Originally, it was celebrated on May 13, but it was changed to November 1 in the 9th century by Pope Gregory IV. However, November 1st is the same day pagans used to mark the celebration of Samhain, which was the beginning of the Celtic winter.
For those who are unfamiliar, Samhain is a name which means "summer's end" and was also the name of the Celtic lord of death, which is how the Celts began to associate that date with death. On the eve of Samhain, Oct. 31, people believed the souls of the dead were allowed to return home for the evening and, perhaps, enact revenge on those who had hurt them in life. For this reason, the Druids built huge bonfires of "sacred oak" branches, and offered burnt sacrifices of crops, animals, even humans. Then they would tell fortunes for the coming year based on the placement of the burnt remains.
About the only thing similar between the Celtic and Catholic feasts is the date and the fact that it has something to do with death. Catholics have their own customs, such as having Masses said for the dead, visiting the gravesites of relatives, etc. But some folks still insist that the Church borrowed All Saints Day from pagans!
In other words, to say we can pray the Rosary while practicing yoga, Nia and QiGong, is like saying we can pray the rosary on All Saints Day while offering burnt sacrifices to God instead of Samhain and then telling fortunes from the ashes. But we all know that this is not how it's done.
The Church always creates something entirely new. There is no underlying posture or movement of worship to the gods of another religion that remain intact. These are either completely removed or fundamentally changed.
In the case of buildings, such as when St. Benedict took possession of Monte Cassino, he destroyed the sculpture of Apollo and the pagan altar found there, then consecrated the building. Under no condition would he have even considered using the same rituals pagans used to worship Apollo and just substitute the name of Jesus.
If we apply these facts to yoga, it would mean that in order to truly do what the Church has done with pagan practices in the past, one would have to change the yoga asanas so that they were no longer positions of worship to Hindu gods. QiGong movements which are founded upon a belief in an alleged universal life force referred to as "the new age god" in the Pontifical document, Jesus Christ the Bearer of the Water of Life, and which are meant to enhance spiritual health and worship the universe, could no longer be used. Nia workouts would also need to be fundamentally changed in order to eliminate all yoga.
It's heartening to me that people like VV are at least beginning to question this trend to adopt and adapt eastern religious practices into so-called "exercises" routines. Particularly in the case of yoga, even the Hindus agree we just can't do that!