Considering the origins and the foundations of the yoga, can a muslim practice yoga as body activity instead as a set of tenets and beliefs?
This is based from country which I resides:
In Malaysia, Fatwa Council has declared that yoga is haram (prohibited) in Islam and Muslims are banned from practising it because incorporate physical movements, religious elements together with chants and worshipping. However merely doing the physical movements of yoga without the worshipping and chanting not considered haram.
Practicing Yoga has no prohibition if it's beneficial. If the Yoga is a sport for mind and body, and is not accompanied by any haram and sin, then it's not prohibited.
Resaale Estefta'at Ayatollah Behjat, Volume 4, Page 569, Question 6506
& Resaale Estefta'at Ayatollah Makarem Shirazi, Volume 3, Question 201
Don't be closed mind. As the quote, if it's not accompanied by any obvious Haram, then it must be OK.
Yes you will do shirk if you do Yoga as Yoga is not an exercise but a way of reaching god in Hinduism. Hindus every morning do SuryaNamaskar incase to the people have not been enlightened as yet should know that it is Yoga. This Yoga pose is basically getting closer to the god of Sun. Each Yoga has its own religious background and hence doing Yoga will definitely make you a shirk.
Various traditions of yoga are found in Hinduism, Buddhism and Jainism. In Hinduism, yoga is one of the six āstika schools (accepts authority of Vedas) of Hindu philosophy. Yoga is also an important part of Vajrayana and Tibetan Buddhist philosophy.
It is clear this is Haram since it is associated with beliefs muslims don't agree with. Besides, Islam came with other halal ways(Salah, duaa, etc...) to reach someone's permanent mind of state . We don't have to follow other ways when Allah showed us the true way to reach tranquility and peace.
If you want to practice Yoga health purposes, you can use other ways which is not associated with any religion such as p90 training or any recommended training online.