Yoga and exercise are not the same. Today, most fitness programs teach exercises, Yoga asanas, pranayama, Tai Chi, aerobics, martial arts, etc or a combination of these. Though all of these are aimed at maintaining and improving health, few understand the difference between Yoga asanas and other forms of fitness methods.
Exercises are aimed at building your muscles and physical strength and endurance. Exercises involve repetition of certain movements aimed at building a certain group of muscles, thereby increasing the muscle weight and improving strength of those body parts. It increases the blood supply to those parts. Most exercises increase your breath rate and heart rate. You consume more oxygen during exercises than when you are doing your daily routine activities.
Yoga asanas on the other hand, work in a totally different fashion. The idea of asanas is not building muscles, but harmonizing the body, breath and mind, thereby contributing to the overall health of the individual. In the Patanjali Yoga Sutras, asana is described as “Sthiram Sukham Asanam”, which means that which gives steadiness, stability and Joy is called Asana. From this definition, it is clear that unlike exercises, you cannot do asanas with strain or tension. There is no extra load on the respiratory and cardiac systems.