A new patent suggests Apple Watch could gain the ability to measure the hydration levels of the wearer, which is a very important metric in health and something that can affect performance during fitness training. These are both areas of great interest for Apple Watch owners and support could arrive on a future version of Apple’s wearable.
The current Apple Watch Series 6 includes a heart rate sensor, a common and well-understood feature of most smartwatches, as well as a blood oxygen sensor, requiring a different type of LED, which is becoming somewhat standard on more expensive models. Accelerometers can monitor movement and the GPS tracks over a long-range. However, the star of the Apple Watch’s health and fitness sensors is its electrical heart sensor located in the Digital Crown and the watch’s back crystal. By touching the crown, a single-lead ECG recording is made, providing any of three results: sinus rhythm (normal), atrial fibrillation, or atrial fibrillation with a high heart rate.
A newly granted Apple US patent describes a different type of sensor for the Apple Watch, one that has the ability to measure the hydration level of the wearer. According to the patent documentation, the new sensor would be placed in the watchband where it can be in contact with the skin. This is necessary as it relies on perspiration to collect the measurement. Hydration can be measured using the electrical conductance of sweat and Apple describes various types of bands with different sensor configurations. A woven fabric band might include electrodes incorporated into the fabric so that they might be partially exposed to the skin. Another might be a solid band with tiny, interconnected cavities that collect moisture via capillary action, taking advantage of the surface tension of water to cause liquid to rise upward to the electrodes. In this case, the electrodes would be kept away from the skin and embedded in the watchband. The reason electrical conductance can be used to measure hydration levels is that perspiration contains electrolytes that conduct electricity.
Hydration level is a measurement of how much water a person has absorbed within their body. This varies, depending on the time of day, liquid and food intake, as well as activity level since more movement generates more perspiration and respiration. Water is lost not only when sweating but also simply by the act of breathing. Being able to check hydration levels quickly and easily with an Apple Watch would help with both fitness and health. Dehydration happens when more water is lost than what is ingested and can have a serious impact on health, including heatstroke, and can also impair performance. At the other end of the scale and occurring less frequently, a person can become over-hydrated by drinking too much water, leading to fatigue and in extreme cases cause confusion, coma, and even death.
It’s much more common for hydration to be measured by medical professionals using blood or urine samples, but this is a slow and expensive system and while it might be more accurate, a relative measurement taken throughout the day and over a period of time could prove to have greater benefits and certainly would increase the accessibility of this type of information. Feeling thirsty is usually a good indicator that it is time to drink some liquid, but it isn’t always easy to understand how much moisture is lost and how quickly since it varies by a person’s activity as well as how hot and dry it is on a given day. Tracking hydration levels via an Apple Watch would be an important advancement to health monitoring and aid users in achieving optimal fitness, bringing this useful data to everyday life.