Bismihi ta'ala

Yes, Muslims are allowed to practice yoga exercise, as long as it does not harm the body or lead to un-Islamic practices or belief. As you know, yoga in its origin is a Hindu spiritual practice, and the word means "to unite" with God. 

Simple yoga stretches are very useful, and the meditation aspect is good as well, but there is also the yoga culture that could be attached to it that a believer must stay away from, like un-Islamic chants, or that yoga alone gives one serenity and inner-peace. 

The great blessing we have as Muslims is what our five daily prayer has for us, which many of us have still not yet discovered. We should also journey into our own Islamic heritage and culture and benefit from its wonders.

With prayers for your success.