What does... ..."strenuous" mean?

A strenuous workout, Jordan.

It's very strenuous.

Three. Not too strenuous.

Doing something strenuous?

I've had a strenuous evening.

Wouldn't do anything too strenuous.

It demands strenuous effort and practice.

They have been very strenuous efforts.

(b) Physically strenuous, arduous or hazardous work;