Freeman was on the field early, then exited during 11-on-11 drills. It was the second time Freeman has left practice early during training camp. The first time was attributed to a stomach illness.
Falcons coach Dan Quinn didn't know the details behind Freeman's heat-related exit this time.
"He had some heat stuff that he dealt with from the first practice and again today," Quinn said. "I didn't get a chance to go in and see him yet, but I'll find out."
The AccuWeather temperature at the end of practice was 90 degrees fahrenheit, with a "RealFeel" temperature of 105 due to the humidity. A number of players, particularly the linemen, took to one knee during practice as a result of the steamy conditions.
Freeman had to exit a practice early in August 2014 as a result of extreme heat.
Tevin Coleman took the first-team reps to start 11-on-11 drills and remained in that role after Freeman left. Terron Ward, who is trying to keep his role as the third running back, moved into the backup role behind Coleman on Sunday. Ward was in a black noncontact jersey as a result of soreness.
The Falcons signed Freeman, a two-time Pro Bowler, to a five-year, $41.25 million extension last week. He scored on a 15-yard touchdown reception in Thursday's 23-20 preseason loss at Miami.