Digital bathroom scales with open source software provide valid dynamic ground reaction force data for assessment and...

Area of Science:

• Biomechanics
• Biomedical Engineering
• Rehabilitation Technology

Background:

• Accurate measurement of vertical ground reaction force (vGRF) is crucial for assessing clinical factors like weight-bearing asymmetry and rate of force development.
• Existing vGRF measurement technologies are often prohibitively expensive, limiting accessibility in various settings.

Purpose of the Study:

• To evaluate the validity and reliability of using modified, low-cost digital bathroom scales for obtaining static and dynamic vGRF data.
• To determine if inexpensive scales can serve as a viable alternative to costly force measurement systems.

Main Methods:

• Four modified digital bathroom scales (two brands) underwent mechanical loading trials (0.01-65 kg) to assess accuracy, hysteresis, and non-linearity.
• Thirty-two adults performed dynamic tasks (sit-to-stand, weight-shifting), with data compared against a Bertec force platform.
• Statistical analyses included intraclass correlation coefficients, Pearson's/Spearman's correlations, Bland-Altmann plots, and mean absolute error (MAE).

Main Results:

• Mechanical tests demonstrated excellent reliability and validity, with hysteresis and non-linearity below 0.2% full-scale.
• Dynamic trials showed excellent cross-correlation, though MAE was higher for sit-to-stand compared to weight-shifting, potentially due to the 10 Hz sampling rate.
• The modified scales achieved high accuracy, detecting force changes as small as 0.01 kg.

Conclusions:

• Digital bathroom scales can be affordably modified to yield accurate vGRF data.
• These modified scales present a cost-effective solution for assessing vGRF in clinical and research settings.
• Further investigation into optimizing sampling rates may enhance dynamic measurement accuracy.