A combination of the words "extra" and "strenuous" used to mean more than just strenuous. Strenuous refers to someone using great exertion or something requiring great exertion, therefore extrenuous refers to someone using immense exertion or something requiring immense exertion.
1000lbs is extrenuous, I would need to inhale pure oxygen for my muscles to stand a chance.
Unnecessarily difficult; made harder, more complicated, or more effortful than it needs to be, especially because of avoidable complexity, bad design, bureaucracy, or poor process.
The password reset should have taken two minutes, but the vendor portal made the whole process extranuous.