IMU – Motion Analysis

IMU in Smartphones

In the analysis of human movements, IMU is unbeatable, at least as long as we wear an IMU device on our body. Nowadays, (almost) every mobile phone and smartwatch has IMU sensors on board, which are used in a variety of apps. Embedded AI is happy to work in this area.

IMU Device and Smartphone

However, what is more interesting is the case where an IMU sensor is supposed to analyze movements, but a smartphone cannot be used for capturing the movement. For example, in a wearable in clothing, integrated in a rehabilitation device, or in a running shoe. For these purposes, it is suitable to manufacture a sensor that sends its motion data, for example, via Bluetooth to a smartphone running an app for evaluation, instruction, or accompanying an exercise (see illustration).

Simplified Technical Explanation

In the illustration, you can see an electronic device that captures motion data and sends it to a mobile app running on the smartphone. Embedded AI builds both software and hardware systems (SW and HW) hierarchically in a layered model.

Simplified representation from bottom to top:

• Hardware Layer (HW) – Electronic modules that operate sensors (here IMU/accelerometer) and actuators, as well as perform data transmission (here Bluetooth (BT)). Physical layer.
• Hardware Abstraction Layer (HAL) – abstracts (simplifies) access to the complex interaction with hardware. In the case of a mobile phone (on the right) or PC, this is the operating system (Android, iOS, Windows, Linux, …). In the case of an embedded system with a microcontroller (on the left), this is a software layer called HAL, which provides certain functions to simplify software-based interaction with hardware modules.

• Applications Layer (SW) – This is where the actual software application takes place, as well as the AI algorithmic topics. On the embedded system (left), the sensor signals are read in via HAL. To keep the radio data rate to the smartphone and thus the energy consumption low, the sensor data is preprocessed depending on the application to extract features. Feature engineering is required here. On the smartphone (right), the raw data or feature data is received and processed in an AI algorithm for motion analysis. The detection results are output to the user by the smartphone app through sound or a GUI (Graphical User Interface) integrated in the overall behavior of the app.
• Protocol Layer – The protocol layer is simplified within the Application Layer in this representation. It is responsible for dividing the data stream into blocks and sending them block by block. At the receiver, the blocks are received and reassembled into a data stream in real time.

IMU in Rehabilitation

Inertial Measurement Units (IMUs) have enabled significant progress in rehabilitation by allowing for precise measurement of motion data. By utilizing IMUs, therapists can accurately track and analyze patient movements. These precise data enable personalized adaptation of rehabilitation exercises to meet the individual needs and progress of each patient.

Additional Benefit of the Smartphone – Gamification

The smartphone enhances the respective rehabilitation exercise. At the same time, the integration of gamification elements in the associated smartphone app, such as point systems, challenges, or rewards, can make the rehabilitation process more playful. Gamification in rehabilitation with IMU not only provides an incentive for patients to work on their exercises, but also promotes adherence to the therapy plan. The playful component creates a positive and supportive environment that makes the rehabilitation process more enjoyable.

Movement Sequences in Training

The integration of smartphones into training for movement sequences heralds a new era of personalized and informative education. By using specialized apps in conjunction with sensor technologies like IMUs, it becomes possible to receive real-time feedback on the execution of exercises.

Persistent Data – Furthermore, the ability to store and analyze training data opens up the opportunity for long-term improvement. Trainees can track their performance over time, identify trends, and adjust their training routines accordingly.

Gamification – The integration of playful elements (gamification) can not only make training more effective but also make learning more enjoyable and engaging. By introducing competitions, rewards, and challenges, learners are motivated to actively and, above all, continuously participate in their own development.

Some Examples

• Skilled Trades: Tradespeople such as carpenters, electricians, and plumbers could benefit from precise training in movement sequences to ensure that their tasks are carried out efficiently and safely.
• Healthcare and Nursing Professions: Aspiring caregivers or physiotherapists can improve their skills by analyzing and optimizing movement sequences using smartphones. This could play a particularly important role in rehabilitative exercises or rescue measures (see illustration).
• Sports and Fitness Education: Aspiring coaches in the fitness and sports fields can use the technology to review, monitor, and improve their own movement characteristics and techniques. Additionally, they learn modern methods of autonomous training that they can later teach to their clients.

The integration of IMU sensors combined with smartphones in the field of sports and fitness has the potential to take training to a new level and increase athlete motivation. This is achieved through:

• IMU Motion Analysis – In almost every sport, movements are crucial – IMU can capture these movements effortlessly through a sensor at the corresponding point of movement. This allows for a detailed analysis of movement sequences, postures, and performances. Athletes and recreational sports enthusiasts can improve their technique and minimize the risk of injuries.
• Smartphones in Training – Smartphones serve as user feedback for displaying motion data from the IMU sensor, creating training plans, and guiding training sessions. Specialized apps can create individual training programs, track progress, and provide personalized feedback in real time.
• Gamification in the Fitness Sector – Gamification elements such as point systems, challenges, and rewards can be integrated into fitness apps to increase motivation. Athletes can compete in challenges, earn virtual badges, and share their progress with others.

• Virtual Trainers – Virtual trainers can create personalized challenges based on IMU data and algorithms. Athletes can compete with virtual opponents or break personal records, which promotes motivation and ambition.
• Exercise Catalog – While not directly related to IMU, using a training software (app) allows users to learn a variety of exercises they may not have known otherwise.
• Community Interaction – Gamification can be integrated into community features where athletes can share their achievements, challenge each other, and provide support. This fosters the social aspect of training and increases motivation through group dynamics.

The combination of IMU, smartphone, and gamification creates not only a technologically advanced but also a motivating and socially connected training environment in the sports and fitness sector. Such applications can make training enjoyable, enhance it, and allow users to benefit from precise data for performance improvement in almost any sport.