The muscular system consists of three major muscle types:

肌肉系統由三種不同的肌肉類型組成：

Cardiac muscles, which are responsible for the function of your heart;

心臟肌，負責心臟的運作；

Smooth muscles, which are responsible for the function of all your other organs;

平滑肌，負責其他器官的運作；

And Skeletal muscles, which are responsible for, as the name suggests, the movement of your bones.

以及骨骼肌，顧名思義，負責骨骼的運作。

Both smooth and cardiac muscles function involuntarily, meaning they operate by themselves.

平滑肌和心臟肌的運作不受意志支配，也就是說它們會自行運作。

Skeletal muscles, on the other hand, function voluntarily and are under our conscious control.

另一方面，骨骼肌則受意志支配而運作。

There are three different skeletal muscle fiber types, known as Type I, Type IIa, and Type IIx fibers.

骨骼肌纖維有三種，分別是 I 型，IIa 型和 IIx 型。

The difference of size, color, contractual speed, contractual force, and energy source classifies each fiber.

根據肌纖維的大小、顏色、收縮速度、收縮能力和能量來源進行分類。

Type I fibers, also known as slow twitch fibers, are the smallest fiber types with a darkish red color.

I 型纖維，又稱慢縮肌纖維，是最小的肌纖維類型，顏色為暗紅色。

It has a fairly slow twitch speed and produces a relatively small amount of force when contracted.

它的收縮速度相當緩慢，收縮時的產生的力量也較小。

It has high amounts of mitochondria, which are organelles within each cell that uses oxygen to produce energy.

它有大量的線粒體，其為細胞內利用氧氣產生能量的胞器。

Although the force generated is fairly small, type I fibers are highly fatigue resistant, allowing it to be active for long periods of time.

儘管I型纖維產生的力量較小，它具有相當高的抗疲勞能力，能應付長時間的身體活動。

They are the primary fibers used during low-intensity activities with steady oxygen consumption, such as walking, jogging, or aerobics.

它是低強度、耗氧量穩定的活動所使用的主要纖維，如散步、慢跑或有氧運動。

Type IIa fibers, aka moderate fast-twitch fibers, are also red but intermediate in size.

IIa 型纖維，又稱中縮肌纖維，也是紅色的，但其纖維大小適中。

These larger fibers typically use a combination of oxygen and glucose as sources of energy.

這些較大的纖維通常以氧氣和葡萄糖為能量來源。

This combination allows for quicker contracting speed and higher force output compared to type I fibers.

相較於I型纖維，其能源組合可加快收縮速度、產生更大的力量。

However, fatigue resistance isn't as high.

然而，其抗疲勞能力就沒有那麼高。

These fibers are typically activated during anaerobic activities that are moderate in duration, such as a mile run, swimming, and short-distance cycling.

這是無氧運動會用到的纖維，如中長跑、游泳和短程單車騎行。

Type IIx fibers, aka fast-twitch fibers, are white in color due to the low oxygen capacity and by far the largest fiber type.

IIx 型纖維，又稱快縮肌纖維，因其氧容量低而為白色，是最大的纖維類型。

It makes up for the lack of oxidative capacity by having extremely high levels of glucose in its stored form of glycogen, producing the fastest twitch speeds and the most force.

肝醣儲存量高使其擁有大量的葡萄糖，以彌補氧容量的不足，因此其收縮速度最快且力量最大。

The downside, though, is that the fiber fatigues quickly, burning out after 15 to 30 seconds.

但缺點是這種纖維抗疲勞能力極低，只能支撐15-30秒。

High-impact, heavy resistance activities such as lifting weights and sprinting, will activate Type IIx fibers the most.

IIx型纖纖最適合高強度、高阻力的運動，如舉重和短跑。

For any activity, your muscles follow a certain recruiting order.

無論做什麼動作，肌肉都會遵循固定的順序。

The slow-twitch, low-force, fatigue-resistant Type I fibers are always activated first.

首先是收縮速度慢、力度低、抗疲勞性高的 I 型纖維。

When Type I fibers are maxed out, Type IIa fibers are activated, and then after those are maxed out, Type IIx fibers are then activated.

I型纖維耗盡後，就輪到IIa型纖維，最後才是 IIx 型纖維。

This order, known as the Henneman's Size Principle, helps minimize muscle fatigue and allows precise motor control by using no more than the force necessary to complete a movement.

這個順序被稱為「亨尼曼的大小法則」，它有助於減少肌肉疲勞，並精確地控制完成每個動作所需使用的力量。

Everyone has a genetically determined amount of each muscle fiber type.

人的基因決定了每種肌纖維的數量。

Some people are born with a predominant amount of a certain muscle fiber, making them effective with activities that favor those fibers.

有些人天生就有大量的特定肌纖維，使其特別擅長需要該肌纖維的活動。

There have been some findings that suggests that Type IIx fibers can change into Type IIa fibers with proper training.

有些研究顯示，透過適當的鍛鍊，IIx 型纖維可以轉變為 IIa 型纖維。

However, this might simply be due to Type IIx fibers showing higher oxygen capacity through physical adaptation.

然而，或許只是生理適應性而使 IIx 型纖維擁有較高的氧容量。

They are, ultimately, still Type IIx fibers.

但它們終究是 IIx 型肌肉纖維。

Based on your exercises, which muscle fibers do you train the most?

根據你平常的運動，你最常鍛鍊哪一種肌肉纖維？

Leave your answers in the comment section below!

請在下面的評論區寫下你的答案！