<Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (August 2017) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (August 2017) (Learn how and when to remove this template message) </Td> </Tr> <P> Aerobics is a form of physical exercise that combines rhythmic aerobic exercise with stretching and strength training routines with the goal of improving all elements of fitness (flexibility, muscular strength, and cardio - vascular fitness). It is usually performed to music and may be practiced in a group setting led by an instructor (fitness professional), although it can be done solo and without musical accompaniment . With the goal of preventing illness and promoting physical fitness, practitioners perform various routines comprising a number of different dance - like exercises . Formal aerobics classes are divided into different levels of intensity and complexity . A well - balanced aerobics class will have five components: warm - up (5--10 minutes), cardio vascular conditioning (25--30 minutes), muscular strength and conditioning (10--15 minutes), cool - down (5--8 minutes) and stretching and flexibility (5--8 minutes). Aerobics classes may allow participants to select their level of participation according to their fitness level . Many gyms offer a variety of aerobic classes . Each class is designed for a certain level of experience and taught by a certified instructor with a specialty area related to their particular class . </P>

Where does the first and second aerobic steps proceed why