"The grounds are traditionally harder in the early autumn, leading into winter."
Players had also had four to five months off, which meant their bodies were not used to the high-impact contact, he said.
Each year, coaches took a "rugby smart course", which covered tackling and contact, and coaching techniques, Mr Parkinson said.
However, rugby was a contact sport and injuries were inevitable, he admitted.
Most common injuries were shoulder, knee and ankle injuries, Mr Parkinson said.
A breakdown of new serious injury claims for Northland last financial year shows 43 were netball-related, 44 for rugby league and 39 were soccer-related.
Nationally, injury stats indicate the four "priority sports" - codes with high numbers of players and injury claim costs - are becoming safer.
The number of new serious injury claims for netball, rugby league, rugby union and soccer have steadily fallen in the past three years - down from 8473 in 2009/10 to 7856 in 2011/12.
The combined injury claims cost taxpayers nearly $230 million, according to ACC.
ACC programme manager for sport Joe Harawira said each code worked hard to reduce injuries.
"We set a target of two per cent reduction in entitlement claims from the priority sports of rugby union, league, netball and football [over the last two financial years]."
The target was well and truly exceeded, with an overall drop of 5 per cent, Mr Harawira said.
"What makes this result even more pleasing is that there were unprecedented increases in player registration in each of these priority sports last year."