Custom IoT Development: Complete redesign of a connected fitness machine

Developing a connected industrial product is about more than just making a machine work.
It involves designing a software, hardware, and data ecosystem capable of evolving, remaining stable over time, and adapting to real-world usage.

In 2018, KERN-IT, a Brussels-based custom software and IoT development company, partnered with RFIT to take over and completely overhaul an innovative connected fitness machine, used notably in professional sports.

This project perfectly illustrates our approach: taking over a complex legacy system, reducing technical debt, and delivering a robust, maintainable solution that is actively used in the field.

The RFIT Project: A weight-free connected fitness machine

RFIT is an innovative strength-training machine, envisioned by project leader and electromechanics expert Franck Fiasse.

Its uniqueness lies in a pneumatic system that simulates resistance, replacing traditional physical weights.
The machine is digitally controlled, allowing for high-precision control over the user's effort.

Key features include:

• Adjusting resistance without mechanical handling
• Performing both concentric and eccentric exercises
• Tailoring resistance precisely to each athlete
• Collecting actionable performance data

The solution is primarily designed for:

• Athletic trainers and coaches
• Physiotherapists
• Rehabilitation centers
• Elite-level sports

Initial Issue: A product held back by technical debt

When RFIT contacted KERN-IT, the product already existed but was in a critical state.
The innovation was real, but the technical architecture prevented any smooth evolution.

Key Challenges Identified

• Machine instability
• Difficulty deploying updates
• Excessive system complexity
• Dependency on proprietary technical choices
• High risk for professional use

Technical Audit by KERN-IT

Our findings:

• An unnecessarily complex global architecture
• Unreadable, undocumented, and unmaintainable code
• In-house, custom PHP framework
• An SQL database misused as a pseudo-NoSQL
• A graphical interface developed in Pygame
• A Raspberry Pi used as the core system
• A rudimentary and non-scalable electronic circuit

The project was functional, but at the cost of major technical debt, making it incompatible with industrial or medical use.

Why custom IoT development was essential

RFIT’s requirements exceeded the capabilities of any standard solution.

The project required:

• Reliable embedded software
• Real-time communication with the machine
• A robust data platform
• A domain-specific interface tailored for healthcare professionals
• A maintainable and scalable architecture

This is precisely the type of context where custom software and IoT development truly show their value.

The KERN-IT Approach: Pragmatism and long-term vision

At KERN-IT, we prioritize a progressive and realistic approach, focused on real-world usage and product longevity.

The project was structured into clear phases, in close collaboration with the project owner.

Phase 1 – Takeover and Security of the Legacy system

Goal: Regain control of the system without interrupting its use.

• Full software, hardware, and electronics audit
• Analysis of mechanical and real-time constraints
• Stabilization of the machine's control system
• Securing data flows

This phase established a solid foundation before any redesign could take place.

Phase 2 – Software redesign on a clear foundation

Backend and data plateform

• Python as the core technological stack
• Flask for the API and data collection server
• Data centralization and historization
• Performance tracking and comparison over time

IoT and Real-Time Communication

• Implementation of an MQTT messaging system
• Asynchronous communication between machine, sensors, and server
• Resilience to network latency and disconnects
• Mise en place d’un système de messagerie MQTT
• Communication asynchrone entre la machine, les capteurs et le serveur
• Robustesse face aux latences et coupures réseau

Embedded Software

• Development of an asynchronous Python control daemon
• High-precision pneumatic pump control
• Real-time data reporting
• Decoupled and maintainable architecture

Phase 3 – Hardware & Electronics Redesign

Software alone was not enough to guarantee the product's reliability.

KERN-IT supported:

• The design of a new control circuit
• The development of a new pump controller
• The integration of more reliable sensors
• The implementation of a force plate to accurately measure load variations

This overhaul delivered:

• Enhanced precision
• Increased reliability
• A technological foundation ready for future product evolution

Phase 4 – Interfaces and User Experience

Primary Web Interface

• New, modern web interface built with React
• Complete phase-out of the Pygame interface
• UX designed specifically for professional use
• Displays tailored for physiotherapists and strength coaches

Mobile Web Prototype

As part of a product exploration strategy, KERN-IT developed a mobile web prototype accessible via any browser.

The goals of this prototype were to:

• Test real-world usage on tablets and smartphones
• Validate remote control scenarios
• Explore ergonomics in actual training environments
• Prepare for a potential mobile extension of the product

This approach allowed us to quickly validate business hypotheses without immediately committing to the costs of a full mobile development.

Business Administration

• Clutter-free interfaces dedicated to healthcare professionals
• Simple session configuration
• Athlete profile management
• Structured exercise catalog

Fonctionnalités clés livrées

Load Control

• Load changes without physical handling
• Instant and precise adjustment
• Enhanced safety for the athlete

Advanced Exercises

• Concentric and eccentric exercises
• Fine-tuning of effort levels
• Adaptation to rehabilitation protocols

Performance tracking

• Automatic data collection
• Detailed session history
• Performance comparison
• Progression analysis

Field Usage and Concrete Results

The RFIT solution was used by Standard de Liège between 2017 and 2023, specifically for:

• Strength and conditioning
• Physical therapy
• Injury rehabilitation

Field feedback highlighted:

• Strong adoption by physiotherapists
• Significant time savings
• Improved precision in athlete monitoring
• Enhanced comfort and safety

Why this project illustrates KERN-IT's expertise

RFIT showcases KERN-IT’s expertise in:

• Custom software development
• IoT and industrial connected objects
• Embedded software
• Python, real-time systems, and data
• Takeover of complex legacy projects

When your project reaches the limits of standard solutions, Kern IT steps in to tackle your critical challenges: reliability, maintainability, and real-world usage.

Developing a connected or industrial product?

You have:

• A complex IoT project
• A connected machine in need of reliability
• An existing product stalled by technical debt

KERN-IT supports you from takeover to industrialization, with a pragmatic and long-term approach.

Contact us to discuss your bespoke software or IoT development project.