strenuous

Adjective

• taxing to the utmost; testing powers of endurance
  • his final, straining burst of speed
    
  • a strenuous task
    
  • your willingness after these six arduous days to remain here- F.D.Roosevelt
    

• characterized by or performed with much energy or force
  • strenuous exercise
    

Related words

• Synonyms: 
  arduous , straining