Wireless sEMG-IMU Wearable for Real-Time Squat Kinematics and Muscle Activation

This work presents the design and implementation of a wireless, wearable system that combines surface electromyography (sEMG) and inertial measurement units (IMUs) to analyze a single lower-limb functional task: the free bodyweight squat in a healthy adult. The system records bipolar EMG from one agonist and one antagonist muscle of the dominant leg (vastus lateralis and semitendinosus) while simultaneously estimating knee joint angle, angular velocity, and angular acceleration using two MPU6050 IMUs. A custom dual-channel EMG front end with differential instrumentation preamplification, analog filtering (5-500 Hz band-pass and 60 Hz notch), high final gain, and rectified-integrated output was implemented on a compact 10 cm x 12 cm PCB. Data are digitized by an ESP32 microcontroller and transmitted wirelessly via ESP-NOW to a second ESP32 connected to a PC. A Python-based graphical user interface (GUI) displays EMG and kinematic signals in real time, manages subject metadata, and exports a summary of each session to Excel. The complete system is battery-powered to reduce electrical risk during human use. The resulting prototype demonstrates the feasibility of low-cost, portable EMG-IMU instrumentation for integrated analysis of muscle activation and squat kinematics and provides a platform for future biomechanical applications in sports performance and rehabilitation.