The fitness tracker market has been booming for a number of years now, with recent data predicting that the $36 billion market will surge to be worth around $114 billion by 2028.  Most of these devices provide relatively rudimentary tracking of the physical activities we engage in, but some provide more advanced functionality, including tracking our sleep patterns and cardiovascular health.

Often these devices will attempt to calculate a level of fatigue based upon our exercise history in a bid to ward off the over-training that can be the bane of amateur and professional athletes alike.  Mostly, these fatigue scores are based on assessing changes in the training volume and intensity of users.

Researchers from the King Abdullah University of Science and Technology have been working on a nanotech-based solution that promises to go a step further.

Testing for fatigue

At the heart of their approach are ultrathin nanomaterials, which they refer to as MXenes, which they hope can allow them to monitor the user’s wellbeing by analyzing their sweat.  The technology has a similar two-dimensional form to graphene, but they are composed of metals, such as titanium, which are non-toxic and have high levels of both conductivity and surface charges.  As such, the material is ideal for biosensors that aim to detect very small changes in chemical concentration.

The project has been a few years in gestation, with the team previously working on a MXene composite electrode that was enclosed within an armband-based sensor.  The device was designed so that it could successfully absorb sweat and detect a number of analytes in it, including lactic acid and glucose.

The team built on this initial work and have been further developing the concept.  For instance, they have been combining MXene sheets with hydrogels, which are water-filled polymers that can stretch and therefore function effectively with human tissue.  They found this was highly effective at working with the kind of movements common during exercise.

“Initially the MXene sheets are randomly oriented within the hydrogel, but once you apply pressure to them, the sheets become more horizontally oriented,” the researchers explain. “Because MXenes have a high concentration of negative charges on their surfaces, horizontal arrangements strongly affect ion movements within the hydrogel, and thus we can measure different levels of pressure change.”

Tracking muscle movements

When a prototype of the device was tested it was successfully able to track muscle movements by the use of electrical resistance patterns that were unique as the mechanical stress caused by physical activity increased.  Through this, the researchers believe their device can accurately gauge fatigue as it builds in our muscles.

“As we exercise and our muscles get tired, the sensor sees the new chemical environment and produces different electrical resistance versus stress curves,” the researchers explain. “By comparing these curves to reference curves for a given sensor, we can determine the pH of the sweat and how fatigued the muscle is.”

The sensor comes complete with Bluetooth connectivity to allow it to hook up to digital devices nearby, and the researchers hope that it could eventually enable athletes to gain real-time measurement of their performance.