न हि जातबलाः सर्वे नराश्चापत्यभागिनः| बृहच्छरीरा बलिनः सन्ति नारीषु दुर्बलाः ||४||
It is not that all men possessing physical strength get their progeny soon. There are persons who are great in body built and strength, but are very weak for sexual activities.
There are some persons who are lean and thin in body built but are sexually very strong and have many children. There are some persons who are weak by nature and some have become weak due to diseases.