Ultra low power2.4GHz SoCs help wireless muscle stimulator to offer consumers pro athlete technology

Technology News |
By eeNews Europe

The Compex Wireless stimulator, which targets professional athletes and serious consumer sports and fitness enthusiasts such as marathon runners and keen cyclists, employs mechanical biofeedback (‘mi-SCAN’) technology to automatically and safely adjust the stimulation settings to the specificities of each muscle.  The stimulator can be used safely and effectively to enhance training regimes and accelerate post training/racing muscle recovery via one of 50 downloadable wireless programs targeting both professional athletes and consumer sports and fitness enthusiasts

Electro muscle stimulation has long been used by elite professional athletes both during training (to stress key target muscles) and between training sessions and competitive events (to accelerate recovery cycles and treat common intensive training ailments such as lower back pain).

The Compex Wireless is the world’s first electro-stimulator to the offer the convenience of wireless to maximize application freedom and comfort without the risk of users getting tangled up in trailing cables. It also gives non-professional users the ability to access the benefits of muscle stimulation on a regular basis, by making it possible for them to set training objectives and download relevant muscle stimulation programs and ready-to-use schedules from a dedicated website.

In operation, a Nordic nRF24LE1 2.4GHz SoC with on-board microcontroller running a Compex-developed wireless networking protocol is located in each of up to four compact wireless circular stimulators (5.5cm diameter, 1.8cm thick, 50g weight). These communicate with another nRF24LE1 located within a wireless controller featuring a 6.1cm color LCD screen and simple user interface used to set up and control the Compex Wireless. Each stimulator can operate for an entire day between recharges from a built-in 450mAH lithium-ion polymer rechargeable battery under highly demanding (two training programs at high power and three recovery programs) usage conditions.

"When we began development of this project we weren’t RF specialists so we decided to recruit an experienced RF engineer and discuss what we were trying to do with a number of local independent wireless design and development labs," says Nicolas Fontaine, R&D Team Manager & Senior Firmware Engineer at Compex Médical in Switzerland (a division of DJO Global) that developed the Compex Wireless. "They all recommended Nordic Semiconductor because of the technical capability of its solutions, quality of service and support, competitive pricing, and operational reliability."

Fontaine continues: "But making this product wireless was still a big challenge. For user comfort all stimulators have to be precisely synchronized within milliseconds of each other at all times and the whole wireless network demanded very low latency so that should the system need to stop [e.g. due to a low battery level in one of the stimulators or by instruction from the user], it stopped immediately and simultaneously rather than disorderly over a few seconds. Finally, the product had to work reliably even in challenging RF environments shared with other Compex Wireless users in close proximity (e.g. during races) and other active 2.4GHz sources such as Wi-Fi and Bluetooth wireless technology. We achieved all of this while meeting all relevant product specifications, compliances and regulations thanks to the dedication of our development team, and support from both Nordic and it’s local European distributor Rutronik."

The Compex Wireless retails for € 1,250 Euros and is available now.

Visit Compex at

Visit Nordic Semiconductor at


Linked Articles
eeNews Europe