Final answer:
Two properties that are inversely proportional to afterload during an isotonic contraction are contraction velocity and maximum force production. The correct option is B.
Step-by-step explanation:
In an isotonic contraction, two properties that are inversely proportional to the afterload are contraction velocity and maximum force production. Afterload refers to the load against which the muscle must work during contraction, commonly used in the context of the heart ventricles during blood ejection.
When afterload increases, the velocity of muscle contraction generally decreases as the muscle must generate more tension to overcome the greater load. Similarly, there is a decrease in the maximum force production due to the higher afterload overpowering the muscle's capacity to generate force.
Neither muscle fiber diameter nor muscle temperature is inversely proportional to afterload in an isotonic contraction.