each muscle has a defined action. muscles have particular roles: stabilizer, neutralizer, agonist, antagoinist) that can vary from one situation to the next. we have single joint muscles, two joint muscleds and multijoint muscles.
it is important to work with muscle groups rather tahn with individual muscles. therefore yoga practice should be varied with a variety of asanas for each muscle or muscle group.
we need to be aware of nerve reflexes when lenghtening a muscle and avoid the fight or fright response that occurs when stretching or tensioning a muscle