Your muscles help power your every move — from walking to running to sprinting. And your muscles are made up of countless cells known as muscle fibers. These hard-working muscle fibers are split into different types, which offer unique benefits and ultimately influence how your body responds to training.
在这里，我们回顾了您需要了解的有关构成许多肌肉的纤维。
A FEW BASICS ABOUT MUSCLE FIBERS
There are two primary muscle fiber types:
- I型或慢速肌肉纤维
These muscle fibers are endurance-focused. That is, they develop force and relax slowly, and have the ability to work for long periods of time without fatigue, according to the “Essentials of Strength Training and Conditioning, 4th ed.” Type I muscle fibers look red under a microscope, thanks to their higher concentration of oxygen-carrying red blood cells. - Type II or Fast-Twitch Muscle Fibers
In contrast to slow-twitch fibers are fast-twitch muscle fibers. These fibers develop force and relax quickly, making them responsible for explosive, power-focused movements. Unfortunately, type II muscle fibers tire out faster, so they’re best for short-duration efforts. Type II fibers often look light red or even white under the microscope, due to a lower concentration of red blood cells.
Most muscles contain a mixture of type I and type II muscle fibers, though some muscles generally have a higher concentration of one type of fiber than other muscles.
例如，据认证的力量和条件专家兼所有者William Kelley称，比目鱼是两种主要小腿肌肉之一，体内I型肌肉纤维的百分比最高。白羊座物理疗法在佛罗里达州劳德代尔堡。原因？比目鱼在以耐力为中心的活动中起着关键作用，从站立到步行到慢跑。凯利说：“这些肌肉整天都在低级别的重力作用，因此它们更具疲劳性，因此具有更多的I型纤维。”
Meanwhile, muscles used more for power — like the glutes, deltoids and quadriceps — tend to have a higher percentage of type II fibers, Kelley says.
What’s more, some people genetically have higher concentrations of specific muscle fiber types than others. These differences are largely responsible for the variations we see in body types and physical and athletic abilities. “Someone who already has a greater percentage of type I fibers will inherently be a better endurance athlete, and someone with a higher type II count will exhibit greater short-duration power abilities — all other things being equal,” Kelley explains.
WHICH MUSCLE FIBER TYPE DO YOU FAVOR?
You can probably tell which type of muscle fibers you have more of based on which activities you’re better at. “If someone is a slow sprinter but can run 13 miles quickly, then it’s a safe bet they are more type I dominant,” Kelley says. If you were a sprinter or a football wide receiver, it should come as no surprise you likely have more type II muscle fibers.
您也可以根据自己的体型来分辨；如果一旦开始训练，就相对容易获得肌肉，那么您可能拥有更大比例的II型肌肉纤维。另一方面，如果您较小，并且不管训练多么艰难，都可以增加肌肉，那么您可能会有更多的I型肌肉纤维。“当然，这是一个概括，”凯利说。
您可以改变肌肉纤维类型吗？
您对I型和II型纤维的比例 - 以及扩展的身体和运动技能，主要取决于您的遗传学。换句话说，您可能无法将I型肌肉纤维变成II型纤维，至少不是我们所知道的。
However, within the two primary muscle fiber types are subtypes, including type I, Ic, IIc, IIac, IIa, IIax and IIx. While you can’t magically turn a type I muscle fiber into a type II fiber (and vice versa),您可以通过训练更改肌肉纤维的亚型。
例如，类型的IIX肌肉纤维产生的所有纤维类型中最大的力量，但也最快地疲劳，使其效率低下。但是，仅锻炼一点将这些类型的IIX纤维转换为IIA型纤维，这些纤维仍然功能强大，但比IIX型持续更长，根据国际体育科学协会（ISSA）。
训练缓慢与快速交换肌肉纤维
Even if you’re not naturally fast — or, on the other hand, equipped for endurance — you can still maximize the muscle fibers you have through training.
Keep in mind your results won’t be the same as someone who has more of the muscle fiber types you’re targeting. “I use the analogy of someone trying to play golf with a baseball bat,” Kelley says. “You will eventually hit the ball into the hole, but it will be harder, take longer and score worse than someone already using the golf club.”
If you want to make the most of your type I muscle fibers, the American Council on Exercise (ACE) recommends prioritizing these kinds of training:
- 等距练习像木板一样，使您的肌肉纤维保持长时间
- High-rep (i.e., more than 15 reps) resistance training with lighter weights
- 巡回训练，您在其中从一个练习到下一个练习，在之间几乎没有休息
On the other hand, if you want to maximize your type II fibers,王牌建议:
- Strength training with heavy weights for fewer reps (ideally 2–6), and taking more rest in between sets
- Performing explosive movements, like kettlebell swings, barbell snatches and jump squats
