fibre types & athletic performances

Question 1

contraction speed: what does the unloaded
shortening velocity experiment demonstrate

Answer 1

demonstrate differences
in contractile speed between muscle fibre
types

Question 2

Contraction speed: describe the different speeds of type I, IIA and IIX

Answer 2

Type I fibres are ≈3 times
slower than IIA and ≈10*
times than IIX

Question 3

limitation to the Unloaded shortening velocity experiment

Answer 3

dramatically different temperatures from our body temp to what the experiment is done at

Question 4

solution to temperature problem in Unloaded shortening velocity experiment

Answer 4

In vitro motility (IVM) assay:
myosin function at molecular level

Question 5

are male fibres stronger than female fibres and why

Answer 5

Male fibres are stronger, more force is generated because their Cross-sectional area are larger

Question 6

describe the specific tensions between male and females

Answer 6

When corrected for the size difference, female fibres develop the same specific tension (amount of force per unit of cross sectional area) as male fibres

Question 7

describe the specific tensions between the different fibres

Answer 7

Type IIX fibres generate greater specific tension compared to type I and
IIA fibres

Question 8

do fibre NUMBER differ between sexes

Answer 8

Studies in the species where all fibres can be counted and compared between homologous muscles (e.g.
mice) indicated that there is no significant difference between male and females

Question 9

can fibres co- express more than one MyHC (Myosin heavy chains)

Answer 9

yes as Slower isoform of myosin heavy chains (MyHC) determines the contraction speed of a fibre unless faster isoform is appreciably abundant (>50%)

Question 10

Does variation in the fibre types have functional consequences?

Answer 10

force generated at high
(but not low) velocity and maximal speed of contraction positively correlate with proportion
of FT fibres.

Question 11

how to Estimate muscle fibres in biceps

Answer 11

Cross-sectional area of the muscle (left)
* Mean fibre cross-sectional area from the biopsy (right)

Question 12

what is the Number of fibres in b. brachii

Answer 12

Number of fibres in b. brachii between 172,085 and 418,884 (>2-fold difference)

Question 13

what does the hypertrophy of the fibres in body builders do

Answer 13

contribute to a larger cross-sectional area (CSA) of the muscle (average CSA in body builders nearly 2- fold larger than in untrained subjects)

Question 14

what does the proportion of fast fibres in the muscle corelate with

Answer 14

the ability to develop dynamic force and power

Question 15

which muscle fibre contract slower

Answer 15

Type 1 fibres contract slower than type 2A or 2X fibres