Current Dark Blues coach Vern Cotter though, tested his 46-man party to the very limit last month with a high-altitude training camp in the French Pyrenees.
But Gray is sure it will all be worth it once the tournament kicks off in September.
"I've been through these camps with Scotland and the Lions and they don't get any easier," said Gray, at the launch of Scotland's World Cup kit.
"It was tough on your body but also tough mentally, just trying to keep yourself going.
"Vern and the other coaches have said they want to make us comfortable in uncomfortable situations and that is what these past few weeks have all been about."
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