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Passive Insufficiency With Finger Flexion
Fully flex the fingers with the wrist held in a neutral position of extension. Now, slowly flex the wrist
and notice how the fingers start extending slightly, and notice that it is not possible to maintain full
flexion of the fingers. This is due to passive insufficiency of the extensor digitorum. The extensor
digitorum is not long enough to stretch over all of the joints it crosses, including the wrist, midcarpal,
metacarpophalangeal, and interphalangeal joints. Under normal conditions when one makes a fist,
the wrist extensors (extensor carpi ulnaris and extensor carpi radialis longus and brevis) hold the
wrist in extension, acting as synergists to neutralize flexion of the wrist produced by the extrinsic
flexors of the fingers so that full lexion of the fingers can occur. The optimal position for grip func-
tion appears to be about 20° to 30° of wrist extension (Soderberg, 1986), and forcefully flexing
the wrist of someone holding a weapon can be used in combat to force the person to loosen the
grip on the weapon.CONCEPT DEMONSTRATION 7.7
FIGURE 7.51 An example of stylized use of the upper extremity in (A) the Graham-based movement and (B) African
dance.
Figure 7.51A: Photo courtesy of Scott Peterson. Dancer: Susan McLain.
Figure 7.51B: Photo courtesy of Keith Ian Polakoff. CSULB dancers Delyer Anderson and Dwayne Worthington.