Yoga is a system of techniques that reflects real and proven scientific, concepts. Many things Western scientists understand about the body have actually been known by yoga practitioners for centuries. Yoga sees the body from a different perspective than traditional Western medicine, but the basic principles are the same.
What we Westerners call nerve plexus, yoga calls chakras (although these terms don't coincide precisely-chakras include psycho-spiritual energy). What we Westerners call spinal alignment, yoga accomplishes through various poses or exercises designed to do what some of us pay chiropractors to do. The human body is in a constant state of flux, continually adjusting internally to the influence of a changing internal environment. Western medicine calls this process homeostasis. Yoga's five sheaths of existence - in essence, the body, the breath, the emotions, the intellect, and happiness-reflect the same need for balance between internal and external forces. The terminology may be different, but the concepts are universal.