Maximum Safe Height of High Heels as Predicted by a Smartphone App Based on YOLOv8

Although high heels are commonly worn for their perceived aesthetic value, they can have negative effects on the health of the foot and lower limbs. Wearing excessively high heels for long periods can negatively affect the wearer's ankles, knees, and spine. In this study, a smartphone app based on the You Only Look Once (YOLO) v8 model was developed to provide users with personalized maximum height recommendations for high-heeled shoes to reduce these health risks. Specifically, YOLOv8n identified heels in videos of participants transitioning from standing flat-footed to tip-toe, and a weighting algorithm was used to identify the maximum appropriate high-heel height. Extreme values were suppressed to ensure that the predicted value was safe and sufficiently conservative. The system was optimized for rapid prediction, and strategies for ensuring accurate predictions against backgrounds of different colors were developed. The system achieved a lower mean absolute error (MAE) of 4.33 mm on white backgrounds than previous studies and is the first reported system to also achieve high accuracy for backgrounds of other colors, namely green and black backgrounds with MAEs of 5.25 and 6.84 mm, respectively. The system has excellent performance and practical applicability. Moreover, unlike our previously developed client-server system, this lightweight system can be implemented locally on a smartphone, greatly improving convenience and privacy.