The Bhoys spent their pre-season in France, where they faced off against Ligue 1 clubs Nice, Lyon and Paris Saint-Germain.
Neil Lennon’s side left France without having won any of their friendlies, but were given a good test from the three Ligue 1 sides.
And Norwegian international Ajer feels their tour of France and the rest of the pre-season campaign has been helpful for side, setting them up for the new season.
Ajer revealed that on a personal basis he used his period back in Norway to put in work into boosting his physical strength and feels that he is improving his game.
“I did a lot of strength work during the summer so I feel I’ve developed that side of my game”, Ajer told the club’s official site.
“I was lucky enough to be back home in Norway without a complete lockdown so I was able to do a lot of training with the ball and some work with my friends while adhering to the health advice.
“It was a good period of hard training and hopefully, it pays off now that we’re back playing football again.
“On an individual level I feel I’ve been improving but the team as a whole has improved too.
“The gaffer has made it clear how he wants us to play and we’re well drilled in the different tactics that he wants us to use. The more we work together the stronger we are as a team.
“This pre-season and the games have helped us improve and it’s set us up well for the season.”
Celtic started their defence of the Scottish Premiership title by crushing Hamilton Academical 5-1 on Sunday and are next in action at Kilmarnock.
