Club and international commitments mean that players sometimes get no more than two or three weeks of summer holidays.
"It's like a summer break, just much longer because usually the players don't have that long off but we were in contact constantly," Klopp told BBC 5 Live Sport.
"The boys were busy, the boys came back here and looked great. We did tests with them and some of them were better than last summer.
"It was not the break you want because it was stressful, mindset wise, nobody knew how it will be.
"That's not a holiday, we were all worried about the situation but the body could rest for the first time for ages for some of my players.
"But the challenges after that long period with no football, they trained pretty much everyday, but without football how would it be? That looks now in the moment really good."