Muscle fiber type | S&C Research
There are three different types of muscle fibers: Type I or slow oxidative fibers; Type IIA or fast oxidative fibers; Answered Apr 2, · Author has answers and m answer views Types of muscle fibers and their relation to strength. See "Regulation of Muscle Fiber Type and Running Endurance by PPARδ" . muscles that are composed predominantly of FT fibers (Costill et al. . fiber in relation to distance composition and VO2max running performance. Mammalian skeletal muscles are heterogeneous in nature. We then consider the variations in fiber type profile in relation to species, gender, and individual.
However, for many diseases it remains largely unclear why certain fiber types are affected. A substantial body of work has revealed molecular pathways that regulate muscle fiber type plasticity and early developmental muscle fiber identity.
Type 1 and type 2 muscle fibers
For instance, recent studies have revealed many factors that regulate muscle fiber type through modulating the activity of the muscle regulatory transcription factor MYOD1.
Future studies of muscle fiber type development in animal models will continue to enhance our understanding of factors and pathways that may provide therapeutic targets to treat muscle diseases.
Introduction The skeletal muscle groups of the mammalian body are made up of bundles of muscle fibers. These fibers can be assigned to different identity classifications "Types"with characteristic movement rates, response to neural inputs, and metabolic styles 12. The primary metabolic pathway used by a muscle fiber determines whether the fiber is classified as oxidative or glycolytic.
More ATP can be produced during each metabolic cycle, making the fiber more resistant to fatigue.
- Muscle Fiber Types
- Skeletal Muscle Fiber Type: Influence on Contractile and Metabolic Properties
As a result, glycolytic fibers fatigue at a quicker rate. Slow oxidative fibers have structural elements that maximize their ability to generate ATP through aerobic metabolism.
These fibers contain many more mitochondria than the glycolytic fibers, as aerobic metabolism, which uses oxygen O2 in the metabolic pathway, occurs in the mitochondria. This allows slow oxidative fibers to contract for longer periods because of the large amount of ATP they can produce, but they have a relatively small diameter and thus do not produce a large amount of tension.
The myoglobin stores some of the needed O2 within the fibers themselves and is partially responsible for giving oxidative fibers a dark red color.
And why do you think that is? Well, what are mitochondria used for? Mitochondria are used in biochemical processes that help us make energy. And the main process they function in that I'm going to reference a couple of times is called oxidative phosphorylation. Now, what is that term mean to you? What does that suggest?
What are the two things that are probably involved in oxidative phosphorylation?
Muscle fiber type
So just as the name suggests, oxidative means oxygen is going to be involved here. And then phosphorylation means that something is going to receive a phosphate group. Phosphoryl- -ation, something will receive a phosphate group.
So the oxidative part applies here to red, the same way that the color red shows up in our arteries. Why are arteries red, and why are veins blue? Well, arteries have more oxygen than veins do.
Muscle Fiber Types
And because of that, the color of our type 1 muscle fibers will be red because they produce more energy from oxygen than type 2 muscle fibers do.
More oxygen is present in type 1, so they're red. And so we could say then that our type 2 muscle fibers will be white.
All right, what about the speed of contraction that we see here? How fast do type 1 muscle fibers contract? Well, let's think about the process of making energy with mitochondria. If type 1 muscle fibers rely on mitochondria for energy, think about all the processes that have to go into making energy through oxidative phosphorylation. You can't just do this right away.
Types of Muscle Fibers | Anatomy & Physiology
You have to have glycolysis happen. You have to have the Krebs cycle occur. There's a lot of things that have to be done. So mitochondria take a while to make energy. So that means that the contraction speed here is also going to be slow because it takes a while to make that energy. And so on the flip side, that means that the contraction speed of type 2, or white muscle fibers, is going to be fast.
What about the conduction velocity? How quickly are we going to be able to receive a neuronal impulse or a nerve signal to type 1 muscle fibers to contract? This is also going to be slow. And the term here is called "slow twitch.
On the flip side, we call type 2 muscle fibers fast twitch muscle fibers.