6.6 Energy Systems vs Muscle Make up

Consider that an individual’s muscle make-up can be helpful in understanding how energy systems supply our body with fuel. While muscles and muscle fibre types are discussed in Chapter 5, understanding how muscles function can help indicate the types of energy systems our body will favour.

Movement in Action

Let’s take a look at two well-known Canadian athletes. On the left is Rory Linkletter, a Canadian Marathon runner who competed in the Paris 2024 Olympics and on the right is Andre De Grasse, a Canadian sprinter. Both are clearly physically fit to compete in their respective sport at a high-performance level. However, each athlete’s muscle makeup is very different from the other.

Muscle fibre types can exist as either type 1 or type 2/2b.

Type 1 Muscle Fibres (Rory Linkletter)	Type 2/2b Muscle Fibres (Andre De Grasse)
Known as slow-twitch fibres and favour aerobic activity. Fatigue slowly and are dense in capillaries and mitochondria, and therefore have a high blood supply. As a result, type 1 muscle fibres are red in colour.	Known as fast-twitch fibres and favour anaerobic activity. Fatigue quickly and house a lower number of capillaries and mitochondria, and therefore a low blood supply. As a result, type 2 muscle fibres are pale in colour.

So, how does this relate to our athletes above?

Well, the average individual will not often demonstrate the same phenomenon as these elite athletes can. Because both athletes are highly trained in their sport, their bodies have adapted to their advantage. Over time, this has caused their bodies to produce more of one muscle fibre type over another. Meaning, Rory Linkletter, who prominently engages in long-distance running, will have more type 1 or slow-twitch fibres. This is because marathon running, or long-distance running, is an aerobic activity that uses cellular respiration for the majority of its ATP demands. However, an Olympic sprinter, like Andre de Grasse, who engages in short but very strenuous bouts of activity, will have more type 2 or fast-twitch fibres. This is because sprinting is an anaerobic activity that uses both the ATP-CP pathway and Glycolysis for ATP production.

Can you alter your own muscle fibre makeup if you are not an elite athlete?

Absolutely, you can. Although everybody is born different, some individuals may be born with more type 1 over type 2, the opposite, or a complete 50 to 50 split of each type. If trained consistently, your body can adapt to the change in demands you place on it.