Apple wants the Apple Watch to be even more efficient at tracking your workouts. The company has been granted a patent (number 11,051,720) for “fitness tracking for constrained-arm usage.”
About the patent
The patent involves a wearable device such as the Apple Watch that’s being used in conjunction with human activities in which a user’s arm may be constrained, such as pushing a stroller. Fitness tracking devices may detect user motion using one or more sensors, such as accelerometers, gyroscopes, barometers, and GPS (Global Positioning Satellite) receivers.
Using motion data obtained from these sensors, a fitness tracking device may calculate and output various fitness data of interest to the user, such as number of steps taken, distance traveled, speed, caloric expenditure, and exercise time. Smartwatches and other arm-worn devices may sense arm swing motion to determine the user’s stride length.
For example, fitness tracking devices may use accelerometer energy to calculate stride length. Stride length, along with step cadence, may be used to determine the user’s speed among other fitness data. However, as Apple notes, if the user’s arm motion is constrained, some fitness tracking devices may underestimate stride length, leading to inaccurate fitness data being presented to the user.
What’s more, some fitness tracking devices may estimate the amount of work being performed based on the user’s body mass and speed. Even if the user’s stride length could be accurately determined when the arm is constrained, the calculated fitness data may not account for the increased work performed when pushing a stroller or other substantial load. Apple wants to overcome these issues with the Apple Watch.
Summary of the patent
Here’s Apple’s summary of the patent: “A system and method for collecting motion data using a fitness tracking device located on an arm of a user, detecting that the arm is constrained based on the motion data, estimating a stride length of the user based on the motion data and historical step cadence-to-stride length data, calculating fitness data using t