When the wrist is flexed, finger flexors may have difficulty forming a tight fist. This illustrates what concept?

The concept illustrated by the difficulty in forming a tight fist when the wrist is flexed is known as active insufficiency. This phenomenon occurs when a muscle cannot generate optimal tension because it is excessively shortened. In the case of the finger flexors, they are responsible for bending the fingers at the joints. However, when the wrist is flexed, these muscles are already in a shortened position, which limits their ability to contract effectively to fully engage the fingers.

As a result, the flexor muscles lose the capacity to produce adequate force for gripping tightly. This directly impacts the ability to form a fist. In contrast, when the wrist is in a neutral or extended position, the finger flexors can work more effectively and produce a stronger grip, since they are not in a shortened position.

The other options refer to different mechanical concepts. Passive insufficiency relates to a muscle being elongated beyond its optimal length, while active sufficiency is generally not a standard biomechanical term. Gravity assistance pertains to the role of gravity in movement but is not relevant to the issue of muscle shortening in this context.