Few business partners can say that the idea of starting a new company together came to them at the end of a sweaty personal training session while sprawled on the gym floor.

But such was the rather unglamorous beginning for the co-founders of boutique gym Ritual.

It was September 2012 and personal trainer Ian Tan had taken just 20 minutes to put his friend, American pro-fighter Brad Robinson, through his paces.

Breathless, sweaty and completely spent, Mr Robinson, now 37, recalls lying on the floor and thinking: "Everyone wants a quick way to get fit. These 20-minute workouts are it."

He says: "Ian had the secret recipe for fitness success - he knew the hack that everyone was desperately looking for."

For the American who was training to be a pro-fighter when he met Mr Tan, the hack in question was the latter's style of high-intensity interval training (Hiit)- back then, a concept that had barely begun to make waves - which the internationally certified fitness coach and kettlebell champion was using to train his clients.

For serial entrepreneur Mr Robinson - who met Mr Tan, now 28, while they were working out at Singapore mixed martial arts gym Fight G in April 2010 - it was a training style that was also, in many ways, revolutionary.

"When I began training in mixed martial arts, I was used to going until I felt like I was dying," says Mr Robinson, who owns five businesses in the securities and lifestyle industries.

He moved to Singapore in 2007.

"At the time, I was not only spending time practising my techniques, but followed that up with hours spent pumping iron at the gym and going for long-distance runs," says the father of two boys.

"In fact, when I first trained with Ian, I scoffed at his workout plan. I thought it was just my warm-up."

Mr Tan, at the time, owned a successful personal training-only gym Thrive in Tiong Bahru.

As it turns out, one training session with him was all it took to throw Mr Robinson's preconceived notions about fitness and strength out of the window.

Mr Tan closed Thrive in 2012 before the duo started Ritual in December the same year.

Instead of pushing him to squeeze in one more repetition or yelling at him bootcamp instructor- style, Mr Tan focused on short but intense complete body workouts such as lunges and push-ups that focused on technique and form.

"What I wanted was to work the body as a machine, not with machines," Mr Tan quips. "I wanted to train him for the sake of improvement, not to the point of fatigue."

In those 20-minute sessions, Mr Robinson found himself pushed to the next level, in a way that his conventional training plans did not manage to do.

The three months of tri-weekly sessions with Mr Tan helped Mr Robinson lose the last bit of weight that he had been unable to shed and gave him "cardio for days" - an expression that was later used by a sports commentator to describe Mr Robinson during his first fight in 2012. He continues to do mixed martial arts today.

However, being an entrepreneur, Mr Robinson saw more to Mr Tan's signature workouts than just the physical benefits. What he saw was the business potential of a boutique gym offering 20-minute workouts - something no other gym in Singapore was offering at the time.

Little did he know that Mr Tan had also begun mulling over the concept of Ritual and that he had even come up with the name.

The only issue? Mr Tan did not think he had the business acumen to pull it off successfully.

With Mr Robinson's entrepreneurship expertise now in the mix, the perfect partnership was formed. The duo wrote everything they wanted to have in their ideal gym on a whiteboard. Within those few hours, they crystallised the concept of Ritual.

"Brad began conversations with me to find out what my gripes with the fitness industry were," Mr Tan, who is single, recalls.

"We vented our frustrations about the hard-selling in gyms and the fact that gyms expect customers to work around their schedules. Those problems became the basis to create our ideal, efficient, people-focused gym."

What they wanted was a Central Business District venue where classes would be available all day - so their time-starved clients would not have to wrap their schedules around their workout sessions.

The sessions would change daily and be offered at three intensities to cater to everyone.

Classes would also be kept small, with two coaches overseeing a maximum of 10 members a session. All amenities would be provided on site so patrons could pop in whenever they felt like it.

They also came up with the idea of a fuel bar, offering healthy fruit and vegetable-rich protein shakes. That way, customers could grab a meal-replacement shake and not have to worry about buying lunch or dinner after their workout.

The two pooled together their savings and after contributions from five silent partners, they were set.

With a sum of $500,000 and six weeks later - during which they found and renovated their third-storey 2,085 sq ft Boat Quay shophouse venue, hired staff and did their branding - the doors to Ritual were open.

Mr Robinson took on the role of chief executive and Mr Tan became programme director - in charge of the coaches, training plans and fitness-related work.

As a testament to the clarity of their initial idea, little has changed about Ritual's physical space, even four years on.

From the dark and grungy interior of their workout space - covered in decidedly aggressive inspirational signs such as "Fat burned is pride earned" and "Go hard or go home sorry" - to the bright and cheery feel of their fuel bar, the space is designed to put clients in the right mood.

The duo have not been content to coast along on their success, despite having found it nearly off the bat after starting Ritual.

"We grew by sheer word of mouth and, three months after opening, had our phones ringing off the hooks. Within five months, we were cash-flow positive," says Mr Robinson.

"But we were always of the mentality that if something wasn't working, we would tear it down and fix it. That's something we've stuck to."

What was not working for them was their booking app - a system they had created to allow users to book a slot for classes. Although there were no technical flaws, the duo did not feel it gave their customers enough flexibility or a good enough user experience.

To that end, two years ago, they invested $200,000 into improving their booking portal and also created a proprietary algorithm that helps their trainers create daily workouts that are scientifically designed to provide a full-body fitness regime.

Version 2.0 of their new booking portal is also a game-changer.

For greater efficiency, it not only allows members to book classes, but also lets them input the time they need to get to the gym, should a slot open up on the waiting list. Members can also pre-book shakes.

They declined to give the number of members they have, but shared that their membership has grown by 35 per cent year on year. Membership fees average $249 a month.

Unsurprisingly, perhaps, just two years after opening, they were getting offers from places as diverse as the United States, Australia, Hong Kong and Dubai to set up partnerships or franchises.

"I had people from New York telling me, this is a New York-type business - you just need to say yes and I'll convert my gym into a Ritual," Mr Robinson says. "At first, we were surprised people overseas knew about us. But at this point, we get an offer nearly every day."

However, they are stepping on the brakes because Mr Tan insists that the quality of their product must not be diluted.

"I wasn't willing to compromise the quality of our trainers or facilities for a quick buck," Mr Tan says, adding that each trainer still goes through four to six weeks of training with him before they work with members.

"For me, consistency was key."

Thankfully, the two were able to test the waters when the LinkedIn offices in Singapore approached them to set up a Ritual for their staff members in November 2014.

They opened a second branch for LinkedIn in Hong Kong the next month and launched Ritual at the British Telecom offices in Singapore earlier this year.

Each of these corporate partnerships has the same facilities as the gym in Boat Quay, with its own coach on site throughout the day.

Now, nearly four years after they first opened their Boat Quay branch, Ritual's second outlet is set to launch in Holland Village next month. Also in the pipeline is an international standalone outlet of Ritual, which will open by the first half of next year.

It is apparent that the duo cannot quite believe their success.

"Four years ago, we were two guys running a gym," Mr Robinson says with a laugh. "To think we might soon become the first Singaporean gym to go overseas? That's just crazy talk. I'm so proud of us, but seriously? That's just surreal."