Table 1. Numerical index for the evaluation of sperm motility

Index	Score	Motility characteristics
I	5	Rapid forward movement
II	4	Slow forward movement
III	3	Slow forward movement and moderate vibrating movement
IV	2	Slow vibrating movement
V	1	Immobility

Sperm activity index (SAI) = [Index score × Movable sperm ratio (%)] × 100.