# Evaluation of DAid® Smart Socks for Foot Plantar Center of Pressure Measurements in Football-Specific Tasks: A Preliminary Validation Study

## TL;DR

Smart socks showed moderate-to-high accuracy in tracking foot pressure during football exercises, but results varied by individual.

## Contribution

Preliminary validation of DAid® Smart Socks for measuring plantar center of pressure in football-specific tasks.

## Key findings

- DAid® Smart Socks showed moderate-to-high correlation with a force platform for relative CoP dynamics in football tasks.
- Absolute agreement varied, with RMSE values ranging from 2.1 to 34.2 mm.
- Individual differences in foot morphology and sensor positioning affected measurement accuracy.

## Abstract

What are the main findings?
The DAid® Smart Socks demonstrated moderate-to-high correspondence with a gold-standard force platform in capturing the directional and temporal characteristics of plantar CoP during FIFA 11+ functional exercises.Absolute agreement varied across participants, with notable differences linked to foot morphology and sensor positioning inherent to the six-sensor textile design.

The DAid® Smart Socks demonstrated moderate-to-high correspondence with a gold-standard force platform in capturing the directional and temporal characteristics of plantar CoP during FIFA 11+ functional exercises.

Absolute agreement varied across participants, with notable differences linked to foot morphology and sensor positioning inherent to the six-sensor textile design.

What are the implication of the main findings?
The system is suitable for applications where relative CoP dynamics are of primary interest, such as monitoring movement patterns and load-shift tendencies in functional tasks.Its portability and ease of use support field-based biomechanical assessment in youth football injury prevention task sequence, particularly when absolute spatial CoP measurement is not required.

The system is suitable for applications where relative CoP dynamics are of primary interest, such as monitoring movement patterns and load-shift tendencies in functional tasks.

Its portability and ease of use support field-based biomechanical assessment in youth football injury prevention task sequence, particularly when absolute spatial CoP measurement is not required.

Background/Objectives: Accurate plantar pressure assessment is essential for injury prevention and rehabilitation monitoring in sports. Wearable sensor technologies, such as DAid® Smart Socks, offer portable, real-time biomechanical feedback and enable data collection in field conditions. However, there is limited evidence on their level of agreement with a gold standard in measuring the foot plantar center of pressure (CoP) in football-specific tasks. This study aimed to determine the preliminary validity of DAid® Smart Socks compared with a gold-standard force platform in measuring plantar center of pressure (CoP) during functional football FIFA 11+ Part 2 exercises. Methods: Ten male volunteer youth football players (mean age 12.2 ± 0.42 years; height 158.7 ± 7.72 cm; weight 46.46 ± 8.78 kg; shoe size EU 39.8 ± 2.68) from the Latvian Football Federation Youth League participated. Eight players had right-leg dominance, two had left-leg dominance; three reported past lower-limb injuries. Plantar pressure was measured simultaneously using DAid® Smart Socks and a 1.5 m entry-level force platform with a calibration factor of 3.2. Center of pressure (CoP) data from the force platform were recorded using Footscan software version 9.10.4. Participants performed two selected FIFA 11+ Part 2 exercises—a single-leg squat (unilateral) and a squat with heel raise, performed bilaterally—under standardized conditions. Each exercise was performed twice, with sock removal and reapplication between trials. Agreement between the DAid® Smart Socks and the force platform was examined using waveform synchronization, root mean square error (RMSE), Bland–Altman analysis, and Lin’s Concordance Correlation Coefficient (CCC) to quantify both relative waveform correspondence and absolute CoP measurement accuracy. Results: Across 160 paired recordings, the DAid® Smart Socks showed moderate-to-high correlation with the force platform for relative CoP dynamics, with 79% of waveforms demonstrating CCC ≥ 0.60. Absolute agreement was limited, with only 16% of recordings reaching CCC ≥ 0.90, and RMSE values ranging from 2.1 to 18.9 mm (X) and 4.3–34.2 mm (Y). Conclusions: DAid® Smart Socks showed moderate-to-high correspondence with the force platform in capturing the directional and temporal characteristics of plantar CoP during functional football tasks, with agreement varying across individuals.