Question

As an instructor, I often have to stand for hours on end. What type of muscle fibers are most at work that allow me to do this?

Slow-glycolytic fibers

Fast-oxidative glycolytic fibers

Slow-oxidative fibers

Fast glycolytic fibers

Answer 1

Slow glycolytic fibers

This is the right answer because it consists of high number of mitochondria and there is slow use of aerobic fibers. Hence the rate which glycolysis takes place is slow and they produce ATP by aerobic mechanism. They are able to supply energy which reduces the fatigue and hence are used during the muscle when used for standing.

The second option is not correct because in this ATP is produced at high rate and hence there is production of high ATP and energy during both aerobic and anaerobic mechanism.

The third option is not correct. These are those muscles which can perform for longer period and hence helps in maintaining the posture through isometric contraction. The slow oxidative fibers are those which are able to contract at relative slow rate and hence during the process it is able to use oxygen and glucose through aerobic respiration which produces ATP.

The last option of fast glycolytic fibers is not correct as it is able to produce short burst of energy leading to increased fatigue. They are mostly used during anaerobic glycolysis and leads to increase in the production of ATP.