Open Muscle's LASK4 Turns a Finger Trainer Into a Smart Labeler for ML-Driven Muscle Measurement

Built around a commercial finger trainer used by musicians, the LASK4 automatically labels data from an arm-worn muscle sensor.

Pseudonymous maker "TURFPTAx," of the Open Muscle project, has created a device that aims to aid hand rehabilitation exercises by measuring the motion of and force behind each finger — and it's being released under an open source license.

"The LASK4 system is a groundbreaking device created by Open Muscle that measures the movement and force of all four fingers," TURFPTAx explains. "The system includes a D'Addario finger training device, custom 3D STL file add-ons, and a custom PCB with electronics for measuring the movement and force. It is also considered a somatosensory device, providing real-time feedback to individuals undergoing hand rehabilitation."

This smart gadget is designed to make data from a forearm muscle sensor more useful through automated labeling. (📹: TURFPTAx)

The LASK4 hardware comes as a part of the broader Open Muscle project, which initially launched to build the Open Muscle Band — an open source wearable for measuring forearm muscle contractions using Hall effect sensors and piston-driven skin contact. LASK4 concentrates, however, on the fingers — and takes a handy shortcut by building around an existing finger strength trainer originally developed for players of string instruments.

In addition to the strength trainer, the LASK4 uses an Espressif ESP32-S2 Mini microcontroller, an SSD1306-based 128×32 OLED display, and a custom-built circuit board. The gadget itself doesn't actively measure the force of a finger press, though: instead, it's designed to be used in conjunction with the arm band to automatically label data by tracking when a given finger presses a key. Using the labels and the measurements from the arm band, it's possible to calculate the force involved through judicious application of machine learning.

"One of the most exciting things about the LASK4 system is its potential applications beyond hand rehabilitation," TURFPTAx claims. "The device was designed to label the training data accumulated by the Open Muscle Band for use in the prosthetics biometric sensor arena. This means that the LASK4 system could potentially be adapted to measure movement and force in other areas of the body, opening up possibilities for new and innovative uses."

More information on the project is available on the Open Muscle website, with PCB design files, 3D-printable STL files, and the MicroPython source code available on GitHub under an unspecified open source license.

Gareth Halfacree
Freelance journalist, technical author, hacker, tinkerer, erstwhile sysadmin. For hire:
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