Answer the following questions regarding muscle fiber types. Information for ans

Question

Answer the following questions regarding muscle fiber types. Information for answering these questions can be found in pages entitled, "Muscle Contraction, Muscle fiber types, and Theory of muscle contraction, fiber types and Training adaptations."

Choose the correct answer for each question. When submitting your answers, provide the full answer, NOT just the letter of the answer you are choosing.

About Diane:

Diane is a highly motivated endurance athlete looking to improve his training and competitive performance by seeking advice from a sports trainer/physiologist. She is initially subjected to an exercise graded treadmill test that involves brief periods of exercise at relatively low intensity, followed by progressive increases in exercise intensity until he was fatigued and unable to continue. Based on these results, a series of optimal exercise intensities at which Diane could train over the next 6 weeks to improve her performance. The proposed training program involved 6 sessions a week: 4 sessions of 60-90 min of continuous exercise at ~65-75% Wmax and 2 sessions a week, 6 x 1 min at 90-100% Wmax, with 3 min rest between bouts.

1) During the initial low intensity exercise periods during the test, the muscle fibre type most recruited would be:
a) I
b) IIa
c) IIx

2) As Diane transitioned from rest to exercise, and from one exercise intensity to the next during the test, there was a slow increase in oxygen uptake, bringing in the other energy systems to meet the energy demands of exercise. Which energy system contributed most during these transitions?
a) oxidation of muscle glycogen
b) glycolysis
c) creatine phosphate

3) As Diane approached the maximal exercise intensity during the test, all muscle fiber types were recruited. Which one produces the most force/power?
a) I
b) IIa
c) IIx

4) Which muscle fiber type has the highest fatigue resistance/endurance?
a) I
B) IIa
C) IIx

Explanation / Answer

1 Answer is A

Muscle fiber types can be broken down into two main types: slow twitch (Type I) muscle fibers and fast twitch (Type II) muscle fibers.[1] Type II fibers can subsequently be broken down into two types: type IIA, which is referred to as "fast twitch oxidative glycolytic", and type IIX, which is referred to as "fast twitch glycolytic". Slow twitch fibers are referred to as "slow twitch oxidative". Type I fibers are characterized by low force/power/speed production and high endurance, Type IIX fibers are characterized by high force/power/speed production and low endurance, while Type IIA fall in between the two.

2 answer is phosphate

3 answer is B

Type I fibers are characterized by low force/power/speed production and high endurance, Type IIX fibers are characterized by high force/power/speed production and low endurance, while Type IIA fall in between the two.

4 answer is A

type I, or slow twitch fibers. These fibers are slow to contract (hence, slow twitch), and can sustain muscular contractions for an extended period of time. This factor makes them ideal for endurance type of events where one is exercising for long durations. They also contain large and numerous mitochondria which aid in their oxidative metabolism (the use of oxygen). These types of fibers are fatigue resistant but are only able produce a relatively low level of force output.

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