Muscle Twitch: Build Jogging Endurance Developing Your Slow Twitch Muscle Fibers

Muscle twitch, fast or slow, is a deciding factor in your body's ability to perform fast exercises (e.g., sprinting) or slower exercises (e.g., jogging) on demand.



The skeletal muscle is comprised of bundles of individual muscle fibers called myocytes. Each myocyte contains many myofibrils, which are strands of proteins (actin and myosin) that latch on to one another and pull. This is what shortens the muscle and causes muscle contraction.

Muscle fiber types are broken down into two main categories: slow twitch (Type I) muscle fibers and fast twitch (Type II) muscle fibers. Fast twitch muscle fibers are broken down further into Type IIa and Type IIb fibers.

The difference between the muscle twitch fibers affects training and physical activity. Our muscles contain a genetically determined mix of 50 percent slow twitch muscle fibers and 50 percent fast twitch muscle fibers.

Slow Twitch (Type I)
The slow muscles use oxygen better to generate fuel (known as ATP) for ongoing muscle contraction over a period of time. They are designed to fire more slowly than our fast twitch muscle fibers and allow us to go for longer distances without fatiguing quickly. This is why slow twitch muscle fibers are great for long distance endurance events such as marathons.

Fast Twitch (Type II)
Fast twitch muscle fibers are better at generating short bursts of speed or strength because this type of muscle twitch fiber uses anaerobic metabolism to create fuel. Consequently, they tire more quickly. Generally, fast twitch fibers contract with about the same force as slow twitch muscle fibers, but they fire more quickly which is the reason they're called fast twitch muscles.

Type IIa Fibers
These are intermediate fast twitch muscle fibers that are a combination of Type I and Type II muscle fibers because they use anaerobic and aerobic metabolism to create energy.

Type IIb Fibers
These fast twitch muscle fibers excel at producing quick, powerful bursts of speed. This muscle fiber has the highest rate of contraction (rapid firing) of all muscle fiber types, but they also tire quickly and can't last long.

If you are consistent with your endurance training, than you'll find your muscle fibers will develop more and improve their ability to cope with and adapt to the stress of jogging further distances.Source: McArdle, W.D., Katch, F.I. & Katch, V.L. (1996). Exercise physiology: Energy, nutrition and human performance

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