Aspas joined the Merseysiders last month from Celta Vigo and is one of four new faces at the club.
But speaking to The Sun, Aspas was keen to point out the difference between how Spanish and English sides prepare for the new season.
Aspas said: "Training has been a little tougher than the sessions in Spain.
"But I know there is a little more running involved in the Premier League. I'm working hard every day to try and earn my place in the team for the first game."
Aspas has been handed the number nine shirt worn previously by Liverpool legends Robbie Fowler and Ian Rush. He is well aware of how important that shirt has been to the club and fans over the years.
He added: "In Spain, they don't attach so much importance to your shirt number as you do here in England.
"But I do know that simply by coming here I have the responsibility to return with interest the money the club has paid for me."
Liverpool start their Premier League campaign with a home game against Stoke City.