Which muscle action can result in passive insufficiency?

Passive insufficiency occurs when a multi-joint muscle cannot lengthen enough to allow for full range of motion at all joints that it crosses. This lack of available length leads to restricted movement due to the muscle being unable to stretch sufficiently in response to the demands placed upon it.

The correct choice pertains to the situation where the muscle is unable to lengthen further. For instance, if a muscle crosses over multiple joints (such as the hamstrings, which cross the hip and knee), they may be in a position where full range at both joints cannot be achieved simultaneously when the muscle is at rest or in a stretched position. This limits movement passively, thus demonstrating passive insufficiency.

In contrast, when a muscle actively contracts, as in the first option, or actively lengthens, as mentioned in the second, the muscle generates tension that can affect joint movements but does not typically lead to passive insufficiency. The fourth scenario, where a muscle sustains maximum contraction, does not address the ability of the muscle to lengthen and similarly does not result in passive insufficiency.