Type 1 and Type 2 muscle fibers are found within the muscle’s motor units. motor units are where your fibers are grouped together inside the muscle. These fibers are controlled by the nervous system. So, your brain sends your muscle a signals to recruit on the appropriate muscle fiber group to power actions as simple as bringing a fork to your mouth (Type 1) to something as complex as a power clean (Type 2). Type 1 muscle fibers are used for lighter, less powerful movements, like distance running in your aerobic zone, and light resistance training and Type 2 muscle fibers are used to power quicker and more powerful movements like plyometrics, sprints and olympic lifting.
Type 1 muscle fibers (slow twitch) have slow contractions, but can withstand fatigue for long periods of time. It’s important to train type 1 fibers to maintain your aerobic base.
Type 2 fibers (fast twitch) are used for fast, strong motions, like a 200 meter sprint, or an olympic lift.
You need to train both Type 1 and Type 2 muscle fibers because you don’t want to be the lifter who can’t run a mile, or the marathoner who can’t do a box jump. By making yourself a well-rounded, more functional athlete, you will be stronger, faster, and more lean.
The more intense the exercise, the more fibers needed. So working big, total body movements where you have to use multiple muscles, or doing short sprints that bring you to a threshold, are the movements that are going to utilize type 2 fibers and these are also the movements that are going to burn the most calories, and torch the deep fat.
According to Runner’s World, “It’s important to train your Type 1 muscles by maintaining an aerobic base through cardio. And i’m not talking a spin class, or a boot camp style class, for “cardio.” It has to be long durations of utilizing the aerobic pathway. “On easy days, you’re using mostly slow-twitch muscle fibers. They have a higher density of mitochondria, high levels of aerobic enzymes and greater capillary density than fast-twitch fibers, which are more involved in higher-intensity training, says Dan Bergland, principal sport physiologist at Volt Sportlab in Flagstaff, Arizona. On easy days, “You increase mitochondria and capillaries and blood flow to those muscles, so they’re better able to utilize oxygen,” he says. “Without that, you can’t do the intense runs.”