Can Usain Bolt Become Prefontaine?

As we learned in class, there are different types of muscle tissue including skeletal, cardiac, and smooth muscle.  For this particular paper, they focused on skeletal muscle.   As we also learned in class, skeletal muscle is powerful, striated, and voluntary (2).  We also briefly discussed how a person is capable of changing their muscle content, but this paper goes into more depth about how the phenotypes of the muscles change in response to different conditions and it also discusses some potential mechanisms. 

Skeletal muscle is composed of different types of muscle, but one type of muscle is usually dominant and that is how we characterize the muscle (2).  These fiber types “differ according to their molecular, metabolic, structural, and contractile properties” (1).  The different phenotypes are affected by “innervation, exercise training, mechanical load, hormones, and aging” (1).   

As discussed in class, we have three main types of muscle fibers; slow twitch (type I), fast twitch (type IIA), and fast twitch (type IIB) (2).  Because of these different muscle fibers and their ATP needs, we can conclude that “myofibrillar ATPase activity correlates with specific myosin heavy chain (MHC) profiles” (1).  This paper also found that there were “pure and hybrid fibers” of muscle and that that the hybrid fibers were needed to transition from one muscle type to another and also they existed for a particular condition (1).  The transition tends to follow “fast-to-slow and slow-to-fast” (1). 

Since there are many properties contributing to the transition of muscle content, one of importance is innervation.  From this paper, they concluded that “fast muscles turn slow when re-innervated by a slow nerve and, and slow muscles turn fast when re-innervated by a fast nerve” (1).  As discussed in class, our brains can rewire our nerves when there is damage to a nerve and also when there are different stimuli (2).  As predicted, the change in muscle fiber content “depends on the duration of the stimulation” (1).  The duration would have to be over an extended amount of time and that stimuli may be exercise training.

Hormones, mainly from the thyroid also contribute to changing muscle fiber content as well as mechanical load (1).   Aging changes muscle fiber content from fast-to-slow twitch (1).

So in conclusion, muscle fiber content can be changed by “innervation, exercise training, mechanical load, hormones, and aging” (1).  Maybe Usain Bolt could become a long distance runner like Prefontaine or vice versa, but they would most likely not be as good as the other at their specialties. 

Reference:

1.       Pette, Dirk; Staron, Robert S. “Transitions of Muscle Fiber Phenotypic Profiles.”  Histochem Cell Biol (2001) 115: 359-372

2.       Skeletal Muscle: Organization, Excitation and Contraction, Mechanics Lecture