The Stoke frontman, who sat out on Monday with a back problem, was hurt in a collision with Shane Long towards the end of Tuesday morning's session and needed treatment on the pitch.
He was eventually able to walk to the coach as he and his team-mates headed back to the hotel and his ankle will be assessed over the next 24 hours, although the Republic are hopeful there will be no lasting damage.
Goalkeeper David Forde and midfielder Glenn Whelan were able to train as Trapattoni pressed ahead with his preparations for Friday night's World Cup qualifier in Sweden.
