... the feeling of doing hard things that exert us ...

[WilliamTaft]

The New York marathon was this week and every time I watch it I think, why does anyone want to do that? And that answer is the outcome and the feeling of doing hard things that exert us is something we value as humans, and it all comes down to the effort paradox – the more effort we put into something, the more we value it.

Source: The Psychology of Your 20s

The author's bio from Penguin Random House:
Jemma Sbeg is a prominent mental health advocate and top podcast host based in Sydney, Australia. She’s best known for her groundbreaking, globally recognized podcast, The Psychology of Your 20s, which she launched independently to make psychological research more relatable to the universal experiences of our twenties. She has a degree and double specialization in psychology from the Australian National University.

Does "exert us" sound natural and correct?

 

[jutfrank]

No, it sounds wrong to me. You can't use 'exert' like that. Although it can be used with a reflexive pronoun as argument (e.g. exert yourself or exert ourselves) it can't be used with an objective case pronoun such as 'you' or 'us'. Moreover, the agent—the thing that does the exerting—must be something with agency, such as a person. In this context, the agent is presented as the hard tasks that require exertion. This is a misuse of the word, in my opinion.

 

[Kontol]

Here aslo https://forum.wordreference.com/threads/exert-us.4153826/