When the wrist extends back (dorsiflexion), the fingers automatically want to curl (tenodesis action). When the wrist flexes forward, the fingers extend. This is passive tension. A figure with a hyper-extended wrist and straight fingers is biomechanically screaming.
Includes dedicated comparisons between male and female arm and hand anatomy. Essential Concepts for Sculpting When the wrist extends back (dorsiflexion), the fingers
Arm and Hand in Motion Anatomy For Sculptors , authored by Uldis Zarins When the wrist extends back (dorsiflexion)