From national team sports and CrossFit Games to code, AI and business development - Marcus Herou has shaped the Swedish fitness industry on several levels over two decades. As a computer engineer graduated from KTH and an early adopter of CrossFit, he was an early adopter of bringing technology and entrepreneurship into the world of training and micro gyms.
Today, he is the founder of Relentless AI Trainer, a platform that uses artificial intelligence to make personal training scalable and accessible to more people. In the new episode of the Sweaty Business Podcast, he talks about the journey from the gym floor to the code row - and why he believes the future of the trainer is about human-machine collaboration.
From martial arts to CrossFit and gym ownership
Marcus' path into the fitness industry started in martial arts and took off when he discovered CrossFit in the mid-2000s. He belonged to the early generation of CrossFit gym owners in Sweden and was then involved in bringing the sports movement and functional training closer together, including in the then start-up project Swe3F (Association for Functional Fitness).
In 2010, he founded Måndagsklubben Falun, a sports club that later became a gym, which has come to symbolize the Swedish micro-gym culture. Over the years, the facility has evolved from a non-profit organization to a commercial business, with a clear core: service, results and community.
"As long as we deliver results and have a close relationship with our members, it doesn't matter which concept we use," Marcus says in the episode.
The CrossFit model and the way forward for micro gyms
In the conversation, Marcus reflects on the strengths and weaknesses of the CrossFit era. As a former competitor - including at the CrossFit Games - he experienced the early, more competitive and intense phase of the sport. He believes that the training itself is still effective, but that the business model has not kept up.
"The CrossFit model is great fitness-wise, but the economic logic is difficult. A lot of boxes are stuck between premium and low cost," he notes.
On Monday Club in Falun the focus has also gradually come to include smaller groups, closer coaching and better follow-up - something Marcus sees as crucial to creating long-term sustainability in a micro-gym business.
WeightTrainer and the road to more people exercising
One of the concepts Marcus highlights is WeightTrainer, which he describes as a way to reach people who would otherwise not start exercising at all. Through a structured onboarding and follow-up, even beginners and people with health problems can get started.
"We see people with type 2 diabetes and obesity getting tangible results. That's the kind of change we want to help create," he says.
For him, development is not about changing philosophies - it's about opening the door to more people and creating a business that is both humane and sustainable.
From programming to AI - Relentless Trainer
As a computer engineer from KTH, Marcus has, in parallel with the gym business, built several software projects in training, including BoxPeak and Gorilla Fitness. Since 2021, he has been working full-time on Relentless AI Trainer, a platform that wants to make personal training scalable.
The app collects training data and customizes workouts in real time based on equipment, injuries, goals and preferences. The goal is to help the user never stop training - through individualization, not automation.
"We are building a system that not only collects data, but understands the body," explains Marcus.
AI and the coaching role - collaboration, not replacement
Marcus sees AI as a tool that can free up trainers' time and improve the quality of every session. But he also points out that good training apps are not built by coders alone - but by people who know both training and technology.
As a graduate computer engineer from KTH and with decades of experience as a coach and athlete, he has an unusual combination of skills. This is evident in his work with Relentless AI Trainerwhere the likes of Sara Sigmundsdottir and Scott Panchik have helped refine the training logic.
"AI can do the manual stuff - counting volume, planning progression - but the human feedback, the warmth, must remain," he says.
He believes the future belongs to PTs and gyms that learn to collaborate with technology rather than compete with it. Small group training, data-driven follow-up and hybrid solutions between digital and physical are, according to him, the next natural step.
Philanthropy, entrepreneurship and business development
A recurring thread in the conversation is the tension between Marcus's philanthropic drives and his entrepreneurial ambitions. With roots in the sports movement and a long background in functional training, he is driven to develop gyms and methods that actually make a difference to people's health - while at the same time ensuring that the operations are sustainable.
"I think it's great when what you build helps others - and at the same time becomes a good business. They are not opposites," he says.
Listen to the full conversation
In episode 178 of the Sweaty Business Podcast we talk about:
- The path from martial arts to CrossFit and gym ownership
- How MK Falun evolved from sports club to gym
- Strengths and weaknesses of the CrossFit model
- From programming to AI - the evolution of the Relentless AI Trainer
- How AI is changing coaching, the PT role and gym business models
- And where training and technology are heading next
Listen to Sweaty Business Podcast #178 with Marcus Herou - one of the most influential voices in CrossFit and micro-gym Sweden.
The episode can be found wherever podcasts are - on Spotify or directly here via our site.
