The specific tension of muscle is about 30 N/cm 2 . a. The cross-sectional areas

Question

The specific tension of muscle is about 30 N/cm2.

a. The cross-sectional areas of the prime movers for elbow flexion and extension have been measured as follows:

Muscles

Cross-sectional area

Biceps brachii

3.6 cm2

Brachialis

6.0 cm2

Brachioradialis

1.5 cm2

Triceps brachii

17.8 cm2

Determine the maximum force that the elbow flexors (as a group of muscles) can exert.

b. Consider the elbow flexors to act together with a moment arm of 4 cm, and the triceps with a moment arm of 2.5 cm. If all of these muscles were activated fully, would the elbow flex or extend?

Muscles

Cross-sectional area

Biceps brachii

3.6 cm2

Brachialis

6.0 cm2

Brachioradialis

1.5 cm2

Triceps brachii

17.8 cm2

Explanation / Answer

Force = specific tension* area

Biceps brachii = 30*3.6 = 108 N

Brachialis = 30*6.0 = 180 N

Brachioradialis= 30* 1.5 = 45 N

Triceps brachii = 30* 17.8 = 534 N

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