Spurs restart their Premier League campaign next week against United.
And Alderweireld told talkSPORT: "I think we are well prepared.
"Some people think that quarantine has become a vacation for us, but this is not so. Yes, we quarantined, but two days after it started, we had already started online training on Zoom.
"We all got the necessary equipment for exercising and maintaining muscle tone. We also ran in the park using GPS. No rest, we trained hard. One is even more difficult than with a team."