The human skeleton contains three types of muscle fibers fast glycolytic (FG), fast oxidative (FO), and slow oxidative (SO). They are categorized based on their speed of contraction and adenosine triphosphate (ATP) regeneration rate (Beline et al., 2021). The paper will describe the three types of body fibers, the relationship between the size principle of motor unit recruitment with muscle fibers, and how understanding muscle fibers is vital to a personal trainer.
The first muscle fiber is SO; these fibers undergo relatively slow contraction and use aerobic respiration for ATP production. Their contractions yield low power for extended periods and have a low exhaustion rate (Beline et al., 2021). Second, FO fibers have a quicker contraction rate and mainly use aerobic respiration. However, since they can adjust to anaerobic respiration (glycolysis), they tire faster than SO fibers (Beline et al., 2021). Finally, there are FG fibers; they undergo rapid contractions and primarily use anaerobic respiration (Beline et al., 2021). Nonetheless, the FG fibers fatigue more quickly than the other muscle fibers. Therefore, the difference between the three muscles depends on their contraction speed.
The size principle of motor recruitment states that “as more force is needed, motor units are recruited in a precise order to the amount of the force output, with small units being engaged first, thus exhibiting task-appropriate recruitment” (Azevedo et al., 2020). The principle relates to muscle fiber type in that motor unit employment measures the number of neurons activated in a particular muscle (Azevedo et al., 2020). Thus, it is a measure of the number of muscle fibers that are activated (Azevedo et al., 2020). Therefore, the higher the recruitment, the stronger the muscle will contract.
The information about muscles is vital for a personal trainer because it plays an essential role in enhancing body health. Knowing the proper exercises to perform in every muscle group has a powerful impact on preventing injuries, and muscle imbalance, improving posture, and building muscles correctly. Therefore, personal trainers with such information can offer the best training for building a healthy body.
References
Azevedo, A. W., Dickinson, E. S., Gurung, P., Venkatasubramanian, L., Mann, R. S., & Tuthill, J. C. (2020). A Size Principle for Recruitment of Drosophila Leg Motor Neurons. Elife, 9, e56754.
Beline, M., Gómez, J. F. M., Antonelo, D. S., Silva, J., Buarque, V. L. M., Cônsolo, N. R. B., & Silva, S. L. (2021). Muscle fiber type, postmortem metabolism, and meat quality of Nellore cattle with different post-weaning growth potential. Livestock Science, 244, 104348.