Greg Eskedjian, MSc. CSCS
Director ofHockey Training & Sports Nutrition
Muscle Fibre Types
The human body contains 3 types of muscle: cardiac, smooth and skeletal. Skeletal muscle is the type of muscle used to produce movement during exercise Cie. quads, biceps, pecs). However, our body contains different types of skeletal muscle as well, that are used in different proportions based on the type of activity performed.
The three types of skeletal muscle found in the human body are: Type 1, Type 2a, and Type 2x fibres. Each fibre type has different characteristics and responsibilities related to exercise. Although we use each fibre type during exercise, exercise intensity and duration will dictate which muscle fibre type is responsible for producing the maj ority of the energy needed.
Type 1 fibre or “slow-twitch” fibre is mostly related to endurance-based activities/sports such as long-distance running or cycling. These fibres are typically smaller, with a smaller force production, but a higher fatigue resistance. Therefore, when exercise lasts beyond a couple minutes, this fibre type is most relied on for energy production.
Both Type 2a and 2x fibres are known as “fast-twitch” fibres because of their speedy contractile abilities. Type 2x fibres are large, with the ability to produce high amounts of force very quickly, although fatigue sets in much faster. Very high-intensity, short duration (under 1 Osec) activities/sports rely heavily on these fibres, such as sprinting, power lifting, and jumping.
Type 2 a fibres are known as more of an intermediate fibre, with characteristics of both Type 1 and Type 2x fibres. Type 2a fibres are intermediate in size, with the ability to produce force quickly, but are somewhat more fatigue resistant than Type 2x fibres. Type 2a fibres are mainly relied on when exercising at a high intensity for about 15sec to a couple minutes. These fibres are predominantly used in high-intensity “stop-and-go” sports such as hockey, football and basketball.
Characteristics of Muscle Fibre Types
| Characteristic | Type 1 | Type 2a | Type 2x |
|---|---|---|---|
| Contraction Speed | Slow | Fast | Fast |
| Fatigue Resistance | High5 | Intermediate | Low |
| Force Production | Low | Intermediate | High |
| Power Output | Low | Intermediate | High |
| Aerobic Enzyme Content | High | Intermediate | Low |
| Anaerobic Enzyme Content | Low | High | High |
| Fibre Diameter | Small | Intermediate | High |
Hockey
Hockey is a “stop-and-go” sport that combines repeated, high-intensity bursts over a prolonged period of time (3 periods). Due to the dynamic nature of the sport, hockey players rely on all fibre types during practices and games. However, Type 2x and Type 2a fibres are predominantly responsible for producing the energy needed play.
During a practice or game, Type 2x fibres are used when a player is sprinting, shooting, and checking because a large amount of energy is needed in a short period of time. During slightly longer high-intensity situations such as battling on the boards, cycling or an intense penalty kill, Type 2 a fibres are mostly responsible for energy production because Type 2x fibres will fatigue at a quicker rate. As for Type I fibres, they are also used during a hockey game, but to a lesser extent. Towards the end ofa long shift or in the period after fatigue has set it, Type I fibres will help us continue to play, although our ability for powerful bursts are gone.
NOTE: Your body never only uses 1 fibre type regardless of the activity. All 3 types are always involved, however, usually we rely on one type of fibre more so than the others to produce the energy we need based on the type of activity.
