Wing Alex Cuthbert has angrily hit back at Jim Telfer's jibe that Wales' players are "lazy".
Former Scotland and British and Irish Lions coach Telfer caused a stir with his comments in a national newspaper.
But wing Cuthbert, who scored the decisive try when Wales beat France to be crowned Six Nations Grand Slam champions last season, said: "It's his opinion, but I know how hard the boys work.
"We have shown in a lot of games where we come out on top as the fittest team, especially in last year's Six Nations, and hopefully we can show it again.
"Everything we do (in preparation) is at a really high intensity to make sure we get as close as possible to that game standard.
"I've worked so hard since coming into professional rugby.
"From where I started, and being in this environment, my game has really progressed. I'm still developing and have a lot more to learn, but each game I will get more experienced."
Wales' Six Nations attack coach Mark Jones added: "There is absolutely nothing lazy about the work ethic of the coaches or certainly the playing staff.
"Three Grand Slams in the last few years suggests being lazy isn't something that goes on here."