The German duo, who represented Germany at Euro 2012, have been given permission to stay at the Allianz Arena to regain full fitness before the new season kicks off
The 27-year-old midfielder had been expected to stay in Germany after being plagued by fitness problems, firstly during the club season and then at Euro 2012.
In a bid to ensure he is ready for the new campaign, Heynckes has opted to put Schweinsteiger on an individual training programme.
"This decision began came about during the European Championship," Heynckes told Bayern's official website. "I monitored Schweinsteiger's performances for Germany very extensively and closely.
"I know Bastian very well. You can learn a lot from his movements, gestures and expressions, and I drew my conclusions from that.
"He had recurring problems with a nerve, but those injuries are healed and forgotten. He is feeling good."
The German coach then commented on the Lahm's situation, as the Bayern captain will be rested after coming off a long season.
"Lahm has played every game for a number of years and always thrown himself into it," he maintained.
"From a purely sporting point of view, it is better for him to recover the Eurso and join the team once we are back from China, just like Bastian."