The 26-year-old was pictured working out in Venice, California, on November 14 evening, just four days after slipping on a puddle and getting stitches, reported Us magazine.
"He looked great. But it was all business. He was concentrating on hitting the weights hard," a source said.
Wearing long sleeves and nylon pants, the former 'High School Musical' heartthrob sported a fresh haircut too.
"He seemed really pensive and was looking around to see who was looking at him," the source added.
The actor completed a stint in rehab earlier this year.