Player "recovery practices", including the possible misuse of prescription drugs, are under scrutiny in an NZRL review into the Kiwis' unsuccessful defence of the Rugby League World Cup.
Chief executive Phil Holden says that aspect is part of a overall debrief of the campaign, which ended in a 34-2 defeat to Australia in last month's final in Manchester.
Holden says concerns arose from team management's observations of "the recovery practices that players have adopted".
That included whether energy drinks were used in combination with prescription sleeping pills.
While that isn't banned under anti-doping regulations, he says player welfare is a big focus for the NZRL.
"It seems to be a practice that is in use within the professional code," he said.
"Over here, we are kind of isolated from that but we want to take a leadership position in this regard."
Holden said he hoped to establish a think tank with other chiefs executives of sporting organisations in New Zealand and also engage closely with the NRL on the issue.
"We want to make sure that, from a player-welfare perspective, everyone understands what is going on and the implications," he said.
Holden said it was too early to say what effect the practice had on Kiwis' performance in the final, "but that is a question we will obviously look at".
He said the review of the Kiwis' World Cup campaign would be wide-ranging and cover coaching, management team structure, resources, accommodation and travel itinerary.
It was likely to be completed by mid-February.
