Validation of a bluetooth-enabled load cell for objective and accessible assessment of lower extremity strength

ABSTRACT

High magnitude loading from performing resistance-based exercise has been found to improve tendon strength and reduce symptoms of Achilles tendinopathy (AT) but is difficult to quantify without specialist equipment. Here, we assess the validity and reliability of a novel AT rehabilitation tool (the “PhysViz” system) compared to a “gold-standard” dynamometer for assessing plantarflexion maximal voluntary isometric contractions (MVIC). 41 participants aged 18–60 completed the study. A within-subject test–retest study design was used to examine and compare the validity and reliability of the two systems during plantarflexion MVICs. Test – retest reliability of the two methods were determined by calculating intra-class correlation coefficients (ICCs) and 95% confidence intervals. Method agreement was assessed with Bland – Altman Limits of Agreement (LoA) analysis. The PhysViz demonstrated excellent test–retest reliability; ICC, SEM and MDC were numerically comparable to the dynamometer (ICC 0.93 vs. 0.92; SEM 2.01 vs. 2.95 kg and MDC 5.58 vs. 8.18 kg, respectively), indicating that the novel system is valid and reliable for measuring plantarflexor MVICs. Future studies should address its utility in monitoring AT rehabilitative loading remotely over time.

KEYWORDS:

• Reliability
• ICC
• limits of agreement
• plantarflexion
• dynamometer
• telehealth

Acknowledgments

The authors would like to acknowledge the contributions of Patrick Wu, Carrissa Moore, and Bryn Lee Meyer. We thank them for assisting in the design, pilot testing, data collection, and data analysis phases of this study. We would also like to thank the numerous ECE students at UBC who were involved in creating and improving the mobile application used in this study for their Capstone design project; we are sorry to not include everyone by name.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Author contributions

Conceptualization (AS, CM, CW, KM), Funding acquisition (AS, CM), Project administration (AS), Resources (AS), Methodology (AS, CW, JS, SP), Investigation (JS, SP), Supervision (AS, CW), Formal Analysis (CW, JS, SP), Writing – original draft (CW, JS, SP), Writing – review & editing (AS, CM, CW, KM).

Additional information

Funding

This project was supported with funding from UBC Faculty of Medicine Multidisciplinary Research Program in Medicine (AS, CM) and VCHRI Innovation & Translational Research Awards (AS).