Apple on Tuesday was granted a patent for a weightlifting tracking system that uses a standalone sensor to transmit metrics to a remote display, which in some cases include a wristwatch.

The U.S. Patent and Trademark Office granted Apple U.S. Patent No. 8,749,380 for a "Shoe wear-out sensor, body-bar sensing system, unitless activity assessment and associated methods" is actually a continuation of multiple patents describing a fitness-related patent ecosystem. Apple has whittled the property down substantially since it was first filed for in 2006.

In the intervening years, Apple culled numerous claim references to shoe wear-out sensors and unitless measurements, but kept the body-bar sensing system and corresponding watch readout. AppleInsider last reported on the property in early 2013 when it was published as a mostly intact application by the USPTO.

As granted, the patent covers a system in which a sensor-laden device attaches itself to a weightlifting bar and counts and displays repetitions. Unique to Apple's invention is the inclusion of a watch for remote readings, possibly hinting at a future or intended use case scenario for the company's much-rumored iWatch.

Illustration of sensor device with external wireless display highlighted. | Source: USPTO

According to the document, the bar device can incorporate Hall Sensors, accelerometers, processors and its own onboard display. Alternatively, number crunching and display duties can be offloaded wirelessly to a user's watch. Sensor hardware clips on to the appropriate fitness equipment, whether it be a bar, dumbbell or machine apparatus, and takes movement readings to count proper repetitions.

In some instances, the sensor package is a standalone unit that can be transported from one piece of equipment to the next, while other embodiments provide for a semi-permanent solution like a bar clamp. Most gyms provide spring-loaded or standard clamps to keep weights from sliding off the bar during rigorous exercise.

From there, a user can read their workout metrics from the sensor device or a wrist-worn watch. Metrics like time intervals between movements are compared against predetermined data to count reps that are then fed to the watch display for easy reading. A user's reps can be further collected and analyzed by the watch device to track progress over multiple sessions.

Alternate sensor implementation.

Apple has yet to announce an iWatch, though many expect the tech giant to introduce a wearable device of some kind later this year. With the new HealthKit framework and corresponding Health app for iOS 8, which can collect raw data from external devices, Apple is making a push into fitness and health-tracking devices.

As for its own hardware, the latest rumors point to a form-fitting wristwatch device with curved OLED screen.