Which preposition to use with strenuousness

of Occurrences 6%

At the word, the two on the mattress turned and grappled each other fiercely, half rising to their feet in the strenuousness of endeavour.

with Occurrences 1%

Life is a "training school" for a future existence, and our place in it depends on the courage and strenuousness with which we have laboured here.

Which preposition to use with  strenuousness