Are Muscle Fibre Types Genetically Determined Or Determined By Training?

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Are Muscle Fibre Types Genetically Determined Or Determined By Training?

The type of muscle fibres an athlete possesses will prove to be a limiting, or promoting factor in the sport an athlete chooses to participate in. There are two main types of muscle fibre, slow twitch and fast twitch. Slow twitch fibres enable an athlete to perform under aerobic conditions whilst fast twitch fibres enable an athlete to perform under anaerobic conditions. Therefore the percentage an athlete possesses of each can be a predictor of how well an athlete will do in a given sport.

The percentage of each type of fibre an athlete possesses is genetically determined. That is it is inherent from parents and other ancestors. This could be shown by a muscle biopsy taken, for example (although not practical in real life), at birth and then again at a later stage in the athletes life. The percentage of muscle fibre types would still be the same. Why is this important? If we look at modern day athletes, in particular 100m sprinters, it is clear to see that the majority of athletes are coloured. Their somatotypes suit sprinting and muscle biopsies have shown that they