Strenuous

The writer's research for the book was strenuous, requiring countless hours of reading and analysis.

The construction workers had to endure strenuous physical labor.

The athlete's training regimen was strenuous, involving hours of intense exercise every day.

The astronaut's mission in space was strenuous, as they had to endure long periods of weightlessness and isolation.

The actress's performance in the play was strenuous, as she had to portray a character with deep emotional turmoil.