Question

Consider a situation when only two torques are acting about the elbow: torque due to the biceps brachii and torque due to resistance (ie, weight). During an elbow flexion exercise, if the biceps brachii generate 250 N of force with a moment arm of 0.05m, what type of contraction would occur if the resistance force was 62 N with a 0.2m moment arm?

a. Isometric
b. Cannot be determined
c. Concentric
d. Eccentric

Answer 1

When the torque generated by the biceps brachii is greater than the torque due to the resistance force, a concentric contraction occurs, resulting in elbow flexion.

Step-by-step explanation:

When only two torques are acting about the elbow, the type of contraction that occurs depends on the relationship between the torques due to the biceps brachii and the resistance force.

In this case, the biceps brachii generate a force of 250 N with a moment arm of 0.05m. The torque generated by the biceps is given by T1 = force x moment arm = 250 N x 0.05m = 12.5 Nm.

If the resistance force is 62 N with a moment arm of 0.2m, the torque due to the resistance is given by T2 = force x moment arm = 62 N x 0.2m = 12.4 Nm.

Since T1 is greater than T2, the biceps brachii is generating a greater torque than the resistance force, resulting in a concentric contraction. This means that the biceps muscle is shortening and causing the elbow joint to flex.