Fulham have been playing in Costa Rica, with Sidwell scoring the side's opening goal in Wednesday's 3-1 win over L.D. Alajuelense.
And Sidwell, while admitting the altitude and humidity has affected the players, is adamant such factors will help the Cottagers be fully prepared for their trip to Sunderland on August 17.
"Of course it had an effect," the 30-year-old told the club's official website.
"It was tough in the mornings when we trained, but the sessions were short and sharp so you just had to make sure you put the maximum effort in and obviously rest when we could.
"It's obviously nice to get minutes under the belt. It's pre-season so we want to work as hard as we can and the more game time you get, the better it is for the start of the season when it comes.
"I think the tricky to reaching peak fitness is more down to games because we had three in a week. We'll be back at Motspur Park soon to train hard and continue to work hard to build up our fitness.
"Obviously we've got the games at Craven Cottage when we're getting close to the start of the season and everyone should be in tip-top condition by then for the start against Sunderland away."