The 41-year-old watched his side draw with Bohemians on Wednesday in what was his first match in charge of the club.
Lampard admits he has focused heavily on fitness in the early stages of preseason, and he is proud of the effort shown by his players.
"We've been really happy with them," Lampard said.
"I have a way of working that can be taxing on the players and we wanted to get straight into it. We have to because we want fitness and intensity in our game.
"I'm happy not just with how they've practically done things but with their attitude in taking everything on."