a.Too much violent exercise. it will increase the production of metabolism and require more oxygen and nutrition which will give more pressure to your heart by supplying more blood; if not, your body would be reduced into oxygen insufficiency.Hard Ten Days

b.Inadequate exercising time. In the beginning of aerobic exercise, it is glycogen that release energy, while 30min later, in place of glycogen, fat starts to release energy, and only about one hour later, fat can become the main supplier of energy. It is almost impossible to lose weight if you stopped exercising at the very time that fat began to break down.MAXIMUM POWERFUL

c.Explosive and fast exercise. human muscles consist of muscle fiber(white fiber and red fiber). In the course of explosive and fast exercise, white muscle fiber can get growth, whose section is relatively broad, thus, tends to grow strong and broad. In a word, in order to get a fully developed or shapely figure, you need to do aerobic exercise (at least one hour) which requires heart beats within 120-160 times/min.Happy Passengers