Going to the gym is meant to improve your health - but it's increasingly leaving gym bunnies with bumps and bruises and strains.
In the past year ACC has approved more than 57,000 gym injury claims- costing the country $35 million in treatment. More than half of the claims were from lifting, carrying or straining.
ACC had approved 57,302 claims from people who said they had been injured while working out as at December 3 2016, more than twice as many as in 2011, figures released to the Herald under the Official Information Act revealed.
The total bill for rehabilitation for gym injuries nearly quadrupled, surging from just over $9 million in 2011 to $35.4 million in 2016.
ACC senior sport injury prevention specialist John Lammas said staff were analysing the factors contributing to the rise in gym injuries.
"ACC supports people leading healthy active lifestyles and will consider opportunities to reduce the incidence and severity of injury where possible."
The Exercise Association of New Zealand - which represents more than 250 health, fitness and exercise organisations - said the growing costs came as the number of Kiwis going to gyms also soared.
In the past five years there had been a reported 40 per cent increase in gym memberships, chief executive Richard Beddie said.
He added determining why more Kiwis were getting hurt while working out would be hard to do.
"It's very clear there are many drivers of the increasing costs, and there is no one single issue to address or easy fix apparent."
Liz Binns, president of Physiotherapy New Zealand, also said the data was difficult to analyse because one person may have had multiple claims.
It was important for gym goers to be under "appropriate supervision", such as by a physiotherapist, a registered and qualified gym instructor or personal trainer, before starting new exercises, she said.
"Knowing that you're working with a registered health professional, you've got a level of certainty of what their level of training has been."
More than half - 27,888 - of the injuries Kiwis claimed compensation for in 2016 were from lifting, carrying or straining.
In particularly competitive gyms, users sometimes pushed themselves "to lift more than they can handle", Binns said.
"Your gym buddies are urging you on, then people set outside their own skill level is, that's when you can strain, overexert, you can cause yourself physical injury."
But she added: "You still have that personal responsibility to know your own fitness level and your own skill level before you engage with any form of exercise".
Anyone experiencing pain or "undue discomfort" while performing an exercise should immediately stop, Binns said.
"You're not going to gain by making yourself be more in pain. You shouldn't return back to exercise until you were pain free from that injury."