Question

1. What are the typical types of fibers in these muscles, how are these fibers organized and how does this architecture affect your selected movement from a functional perspective? (for runner muscles )

2.How is the mechanical behavior of a single muscle fiber in tension different from the whole muscle? What is the functional value? (for runner muscles )

3.5. Do your selected muscles cross more than one joint? What are disadvantages associated with muscles that cross more than one joint? (for runner muscles )

Answer 1

Ans 1:

• There are three types of skeletal muscle fibers present in runner muscles.

1. Type I, known as slow-twitch fibers, are the body's primary method for less explosive, sustained movements. They do not contract forcefully and thus requires less energy to fire, which makes them well suited to long distance running. These muscle fibers house our main supply of oxygen boosting power plants - mitochondria, myoglobin and capillaries.
2. Type IIx are best known as fast-twitch muscle fibers. These muscle fibers are primarily responsible for fast, explosive movements like sprinting. They lack the endurance-boosting ability of slo-twitch fibers and can only be used for short periods of time.
3. Type IIa are called intermediate-twitch fibers. These ara a blend between slow and fast twitch fibers. They have some aerobic capability, but not as much as the slow-twitch fibers, and they can fire more forcefully, but not quite as explosively as the fast-twitch fibers.

• All these three fibers are organized with respect to a process callled recruitment ladder. The recruitment ladder is a way of envisioning how and when each fiber is activated. At the bottom of the ladder, muscle have slowest, least explosive, Type I, slow-twitch fibers and at the top of the ladder, muscle have Type IIx, fast-twitch fibers. In-between these two fibers, Type IIa, intermediate-twitch fibers are arranged.

• This organized fibers architecture i.e. ladder affects the selected running movement based on how much force body need to generate to sustain a given pace. If runner head out to the streets and begin running easy, the body would start by using Type I slow-twitch fibers. If runner were to pick up the pace, the body would start recruiting some of the Type IIa intermediate-twitch fibers to supplement the need for more power from muscles to generate more force during the stride. Finally, if runner were to sprint across the road to beat traffic, the body would then engage the Type IIx fast-twitch fibers to give body the explosive burst needed to sprint.