He said: "Not playing for England has given me a new lease of life with United and it's certainly helping me at this stage of my career.
"It's hard to really say what effect on me not playing international football has had but I'd say it's helped because there are fewer demands on my body, less travelling and fewer matches.
"When the international matches come around on the calendar you get your 10-day breaks here and there through the season which, at my age, is a good thing.
"It means you get a break from the hurly-burly of playing every week in the Premier League, so it must help.
"The Premier League is very tough and even though I'm not playing internationals any more, it would be hard for guys like myself and Ryan Giggs to be playing twice a week at this level. So when the internationals come around and everyone goes off with their national teams, it's a great chance to have a rest, and sometimes after a break like that I feel really refreshed.
"Hopefully, that's been good for me and the team, too. It's still hard work when we do training for a couple of days and the other lads are away but it's nice to get that break during the season and I know Giggsy feels that way, too."