Murray beat Fabrice Santoro in the opening round at Wimbledon
Andy Murray says he is aiming to increase his body strength in order to reach the latter stages of Wimbledon.
The 21-year-old Scot missed last year's championships through injury and has yet to reach the quarter-finals of a Grand Slam.
"You've got to see me in the gym - I was doing chin-ups with a 20kg weight attached to me a week ago," he said.
"My five-set record is much better and I've put on nine pounds since November and I want to put on the same again."
Murray's fitness has been questioned in recent years and former Wimbledon champion John McEnroe recently said he did not think the British number one worked as hard as his rivals Rafael Nadal and Novak Djokovic.
But Murray insists he is in good shape and can make good progress at this year's championships.
"I want to try and win the tournament and if I don't do that I'll be disappointed," he told BBC Radio 5 Live.
"But to get deep into the second week will be a good run for me.
"The courts are slower but I still think if you can get a high percentage of first serves in, and if you're serving over and above 130mph, it's tough to return. It's something I have worked on a lot.
"The deeper you go in the tournament, the more you are going to have focus on putting a high percentage of serves in.
"The second serve is something you have to keep away from your opponent's strengths, it's more about getting the placement right rather than the pace you're hitting it."