Home -> Advanced Training -> Cardio Training Q&A -> Aerobic or Anaerobic Exercise         Q. Do some people react favorably to anaerobic exercise but not aerobic exercise? If so why?         Some people do, in fact, react more favorably to the more short duration, high power anaerobic exercise (such as sprinting or weight training) as compared to longer duration, low power aerobic exercise (such as walking or jogging). The main reason for this is muscle fiber type. There are two main types of fibers in your muscles. Slow Twitch: These are also known as Type I muscle fibers. They are responsible for long-duration, low-intensity activity such as walking or any other aerobic activity. Fast Twitch: These are known as Type II fibers (they are divided further into Types IIA and IIB). They are responsible for short-duration, high intensity activity. Type IIB fibers are built for explosive, very short-duration activity such as Olympic lifts. Type IIA fibers are designed for more moderate-duration, high-intensity work such as weight training. The difference for the trainer is the ratio of slow twitch to fast twitch fibers. A marathon runner may have 80% slow twitch fibers in his or her legs and, therefore, be an amazing aerobic athlete. An athlete such as a sprinter may have 80% fast twitch muscle fibers in his or her legs and be an amazing anaerobic athlete. This type of person would not react favorably to aerobic exercise due to the high percentage of fast twitch fibers in their legs. They would tire quickly because most of their muscle fibers are designed for short bursts and, most likely, would lose motivation rapidly.   Metabolic Surge - Rapid Fat Loss Lose the Fat and Keep the Muscle!   Get a free sample of Metabolic Surge now!    Learn how to use proper training and nutrition   to lose bodyfat while keeping and even   building muscle mass.    This free course will give you programs,    training techniques, supplement information,   exercise technique and more! Your E-Mail:   Return To Cardio Question Index