Understanding Fast and Slow Twitch

Want to take your training and understanding to the next level? One way to increase positive results from a workout or training program is to better understand the body and its muscle groups. A key factor to understanding these groups is to understand the fast twitch and slow twitch muscle groups, along with how to better train them.

What are fast and slow twitch muscles? Never new muscles twitched fast and slow? Never heard of any of this type of voodoo before? Don’t worry, here’s the basics.


Slow twitch muscle fibers, or Type 1 fibers, are the muscle fiber groupings that twitch slowly and are meant for endurance muscles. These muscles have the slowest-contractile speed, highest oxidative/aerobic capacity, smallest cross-sectional area, and lowest glycolytic/anaerobic capacity. Due to their slow contraction rate, these muscles are typically used for endurance activities rather than short-burst power activities.

Activities Using Slow Twitch Fibers

  • Swimming
  • Cycling
  • Long Distance Running


Type 2A and 2B twitch fibers are regarded as the fast twitch muscle fibers. Type 2A contract the fastest out of the two, while Type 2B twitch intermediately between slow and fast twitch fibers. Twitch fibers like 2A have the lowest oxidative rate and the highest glycolytic capacity, making them perfect for short bursts and power lifting. Type 2B, since they fall in the middle, are generally utilized in between the uses of slow and fast twitch fibers.

Activities Using Fast Twitch Fibers

  • Power Lifting
  • Sprinting
  • Bodybuilding


Your muscle groups are made up of lots of muscle fibers. No really, thousands upon thousands of muscle fibers. Controlling these muscle fibers are motor neurons, which are connected to the spinal cord and brain. These neurons, both slow twitch neurons and fast twitch neurons, in turn make the muscle groups contract slowly and quickly. When someone does a light exercise, they may only require type 1 fibers. However, when they become exhausted, they may call upon 2A and 2B fibers. There’s a lot going on here, but an individual can become exponentially stronger if they learn how to harness all of their motor units rather than just 1 group.

For example, consider a power lifter. Power lifters are known for their immense strength and power. How do they lift such heavy weights? They have learned to harness the full power of all of their muscle fibers so that they can utilize both short bursts and endurance. Powerful stuff, right?


A training program utilizes both fast and slow twitch muscle fibers. The body will utilize type 2A and 2B muscle groups for short burst and powerful workouts. Type 1, or the slow twitch muscle fibers, are used for endurance exercises. Learning how to efficiently utilize both types of muscle fibers will ensure maximum gains and muscle stamina for anyone, whether just starting their program and continuing the program.

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