Here is a video clip titled "The Health Benefits of Yoga" broadcast on ABC’s Good Morning America TV Show. There is a segment with Sat Bir Singh Khalsa, Ph.D. where he talks about the scientific studies done which shows the benefits of doing Yoga.
Whenever I hear Sikhs ragging on Yoga saying it is "against Sikhi" I can only laugh at the ignorance and lack of understanding of Yoga. Some of this opinion seems to be from the perception that Yoga = Hinduism. There is a strong will to want to dis-associate from anything Hindu-ish. I can understand where this comes from with all the things that have gone on in India in the past 50 years, but in fact, Yoga is not a religion and is not a Hindu practice.
The other mis-understanding relating to Yoga is that "the Gurus were against Yoga". In case you didn’t know Yoga means "Union" (to Yoke or Unite) and this "Yoga" can come in so many forms. We as Sikhs practice many types of "Yogas" if you look at it from this perspective.
People often mention to me various parts of Gurbani (Sidh Gosht and others ) as an indication of the Guru’s being against Yoga. When in reality if you look at the big picture of the circumstance and the examples shown, the lessons are more about the not leaving society to seek God, and how it is fruitless trying to seek "super natural powers". Anything in life that might have benefits, when out of balance can be bad. The inbalance is the issue…not the normally the thing itself.
I think it is time that Sikhs open their minds a bit and stop being so judgmental about something they know little about. In my experience Kundalini Yoga helps create clarity of mind and a healthy body, which is a GOOD THING. Many Sikhs I see have way too much desi ghee, and could do with a bit of Yoga (or some form of exercise). However, Kundalini Yoga goes beyond just exercise, but however you want to rationalize it in your mind, go for it. I’m not trying to convince you to do Yoga. That’s up to you. Just open your mind a bit and learn something about it so you don’t judge others out of ignorance. Wether you do yoga or play basketball, bottom line is that you should DO SOMETHING to take care of your "body temple". We often just think that if you just do Bani then all is well and leave out taking care of our bodies. We are the Sant Siphi (Warrior Saints) and if we are to be in a position to help and serve others we must be ready, physically, mentally, spiritually.
Ps. If you want to try doing some Kundalini Yoga, you can search for a certified kundalini yoga teacher in your area.