Most traditional exercise is termed a “workout”, likely because the objective and the experience is of making your muscles perform work. This consumes energy, produces heat and strengthens them at the same time. The specific muscles and tissues engaged in the type of exercise you perform are repeatedly engaged and become progressively stronger. You can generally work out while watching TV or performing other work that engages your attention, since your body is performing a repetitive routine.
Such exercise primarily activates the Sympathetic side of your Autonomic Nervous System (ANS), as your blood pressure and pulse rate rise as you work out. It also releases endorphins, good chemicals that create a feeling of wellness and elevate mood.
When you are practicing yoga exercises, especially yoga asanas, your objective is to bring balance into your system and establish a mind-body connection. The term Hatha Yoga is generally used for such practices, a word meaning balance (Ha – Sun, Tha – Moon). The balance is not only between the physical left and right sides for the body, or the front and back; but also between the Parasympathetic and Sympathetic sides of your ANS. Yoga asanas involve the process of moving into a posture and holding it, which engages your attention on the anatomy and physiology of the pose. Thus the mind and body come together, establishing a neural and chemical connection between the brain and the smallest tissue that gets engaged. A listening channel is opened up between often ignored parts of your body that you likely weren’t even aware of (except when they hurt and grab your attention through pain).
Practicing yoga asanas also engages your breath along with the attention. As you “breathe in” to a pose and then “breathe out” of it, you consciously experience the life force coursing through your body in the form of nerve signals, neurotransmitters, chemical ligands, ATP (Adenosine triphosphate) and oxygen involved in energy transmission and cellular nutrition. Over time, this establish healthy breathing habits and self awareness, which result in good health and wellness of body, mind and spirit.