British number one Andy Murray says he can train at "100%" again following the back operation he had last year.
The 27-year-old had surgery in September 2013 and was out for three months before returning in December.
"I wasn't able to train as much at the beginning of the year because of my back," said the 2013 Wimbledon champion, who will play in the Rogers Cup in Toronto this week.
"Now I can start training again 100%, not holding back."
Murray's appearance in Canada is his first outing since the defence of his Wimbledon crown ended at the quarter-final stage in July.
He has been given a bye into the second round of the Rogers Cup and will play Nick Kyrgios, who defeated Santiago Giraldo in straight sets. Australian Kyrgios beat the then world number one Rafael Nadal to reach the quarter-finals at Wimbledon.
Murray will be using the tournament to help improve his world ranking, which has dropped to nine, and as preparation for the US Open, with the final major of the year starting on 25 August.
"I felt maybe what I was missing was just some physical strength," said the Scot.
"When you come back on the tour it is a bit of a recovery process.
"Over the French Open and Wimbledon my back felt very good. Physically, it was fine."
Murray said on Sunday he wanted former Wimbledon champion Amelie Mauresmo to remain his coach for the "foreseeable future".