There is a sequence of practicing yoga . It’s not that you can start practicing a particular asana all on a sudden without energizing with Warm-up exercises or you will receive injuries. Yoga is practiced as a sequel to ‘physical’ exercises. You go for physical warm-up session for a period which will lead to sweating. You then ‘cool down’ with rest, preferably with savasanam before you go to the prime yoga session with your choices of yoga asanas. The mudras are practiced after that and the pranayamas (breathing yoga exercises) at the end. This is the sequence of yoga practices. Even for other physical exercises you have to have a beginning session of warm-up exercises without which you run the risk of getting ‘injured’.