If yoga was just a physical training or sport exercise, there was no reason in asking whether it is allowed for Muslim to practice it or not. As yoga has been taken by some Hindu groups and propagated as a Hindu practice, many Muslims from the subcontinent have doubts about it as they don't want to support Hindu propaganda.

I advise you to seek the opinion of respected scholars in your area whether yoga is taken by people there as just sport or people take it as part of Hindu religious practice?

If your community or your society looks at yoga as part of Hindu practice, then you as a Muslim should not support spreading their propaganda.

If your society looks at yoga as a sport like football or basketball or swimming which has no link with Hindu or any non Muslim faith, then it will be allowed for you to practice it. 
Wassalam.