Asthenic means weak. In asthenozoospermia motility of sperms is affected. Normally sperms after liquefaction in the vagina swim vigorously to reach the fallopian tube where fertilization takes place.
There are generally two types of motility. Progressive motility is where the sperms move linearly.
Non progressive motility may be either when the sperms move sluggishly or go around and around in the same place.
Causes of mobility reduction of sperms:
Infections, Varicoceles, Obstruction could all be a reason for a reduction in motility. The World Health Organisation (WHO) guidelines require motility to be in the range of about 40%. Sperm motility has a definite role to play in improving pregnancy rates.