"It's what the South Wairarapa needs, so it's good to be able to offer it and everyone seems to be enjoying it."
Ms Keen, a pharmacy technician and also from Masterton, is looking after the gym's behind-the-scenes business affairs.
Mr Manley and Mr Henderson are both personal trainers, which means there is always one on site, allowing people who have never weight trained in their lives to give it a go.
"A lot of people don't realise how beneficial weight training is. It's good for strengthening your muscles, getting in shape and for well-being," said Mr Manley.
Mr Henderson said someone would always be available to give gym-goers guidance and keep them progressing.
New members were given a free introduction where they were taught how to use all the equipment correctly.
"It gives them a good base and platform to work from," said Mr Henderson.
Operating seven days a week, from 5am to 11pm, a monthly membership to the gym costs $60, $90 for couples, with no contract or joining fee.
It also offers a $10 casual rate for people visiting the area.
The trainers said they could cater to everyone's needs, from cardio, weight training, circuit training to sport specific, and a mix of younger sports players to older people had been joining up. "We cater to whatever the members want and we are here to help them reach their goals," said Mr Manley.
Strength Nation boasts around 60 brand new machines, with four unique ones found nowhere else in Wairarapa.
It has a donkey calf, which is a weight stack machine, an isolated seated row, isolated lat pull down and an isolated shoulder press, which are all plate loaded machines.
"This gear has got a lot of life in it so we want it to be used," said Mr Henderson.
Each day a different "workout of the day" goes up on a board, for those without a specific plan or routine or those wanting a new challenge.
"We try and keep our minds as open as possible, which benefits the customers and us.
"Come in and give it a go, exercise is good for the mind," said Mr Henderson.
"There's nothing like this in this area and we're offering a commercial gym with commercial equipment, but it's friendly," said Mr Manley.
"We like keeping a friendly atmosphere, making people want to come and letting them enjoy it."