Detecting Exercise-Induced Temperature Distribution Changes at the Knee Using a Wearable Array of Thermistors

The Heat Distribution Index (HDI) has been used to capture the abnormal variance in knee temperature distribution as a proxy for inflammation in osteoarthritis. HDI has been derived from thermal camera (TC) data, but its use has been limited to static conditions, as TCs are impractical for dynamic a...

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Main Authors: Benito L. Pugliese, Virginia Civeriati, Adam S. Tenforde, Danilo Demarchi, Paolo Bonato
Format: Article
Language:English
Published: IEEE 2025-01-01
Series:IEEE Access
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Online Access:https://ieeexplore.ieee.org/document/11043146/
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author Benito L. Pugliese
Virginia Civeriati
Adam S. Tenforde
Danilo Demarchi
Paolo Bonato
author_facet Benito L. Pugliese
Virginia Civeriati
Adam S. Tenforde
Danilo Demarchi
Paolo Bonato
author_sort Benito L. Pugliese
collection DOAJ
description The Heat Distribution Index (HDI) has been used to capture the abnormal variance in knee temperature distribution as a proxy for inflammation in osteoarthritis. HDI has been derived from thermal camera (TC) data, but its use has been limited to static conditions, as TCs are impractical for dynamic assessments. This study evaluates the feasibility of using a wearable array of thermistors to assess HDI changes in response to exercise, using TC data as reference. Ten healthy participants were enrolled, and knee skin temperature was measured pre-, post-exercise, and during a cooldown period of approximately 30 min. The thermistor-based system detected a significant HDI increase post-exercise (<inline-formula> <tex-math notation="LaTeX">$\Delta HDI=0.76^{\circ }\text {C}, p\lt 0.001$ </tex-math></inline-formula>) consistent with the TC results (<inline-formula> <tex-math notation="LaTeX">$\mathrm {\Delta HDI=0.71^{\circ }C, p\lt 0.001)}$ </tex-math></inline-formula>, with no statistical difference detected between the two methods <inline-formula> <tex-math notation="LaTeX">$\mathrm {(p\gt 0.05)}$ </tex-math></inline-formula>. During cooldown, both systems tracked recovery trends without detectable differences <inline-formula> <tex-math notation="LaTeX">$\mathrm {(p\gt 0.05)}$ </tex-math></inline-formula>. The mean HDI error for the thermistor array was 0.20&#x00B1;0.36&#x2218;C. Simulations assessing performance and sources of error showed negligible bias in HDI estimates regardless of the number of thermistors, while variance decreased as thermistor count increased. A more uniform sensor distribution across the region of interest improved accuracy over clustering near its edges, while misplacement had minimal impact except for rare outliers. These findings support the feasibility of a wearable array of thermistors for assessing exercise-induced HDI changes. Improvements in sensor placement to maximize skin contact while allowing for perspiration may enhance reliability. This work lays the foundation for real-time thermal monitoring and may aid in developing wearable tools to monitor patients with knee osteoarthritis.
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spelling doaj-art-ea2e57e5f7704a89b563df609c57f2c42025-08-20T02:20:40ZengIEEEIEEE Access2169-35362025-01-011310675910677010.1109/ACCESS.2025.358149111043146Detecting Exercise-Induced Temperature Distribution Changes at the Knee Using a Wearable Array of ThermistorsBenito L. Pugliese0https://orcid.org/0000-0003-4456-9226Virginia Civeriati1Adam S. Tenforde2https://orcid.org/0000-0002-3966-8070Danilo Demarchi3https://orcid.org/0000-0001-5374-1679Paolo Bonato4https://orcid.org/0000-0002-1818-1714Department of Electronics and Telecommunications, Politecnico di Torino, Turin, ItalyDepartment of Physical Medicine and Rehabilitation, Harvard Medical School, Spaulding Rehabilitation Hospital, Boston, MA, USADepartment of Physical Medicine and Rehabilitation, Harvard Medical School, Spaulding Rehabilitation Hospital, Boston, MA, USADepartment of Electronics and Telecommunications, Politecnico di Torino, Turin, ItalyDepartment of Physical Medicine and Rehabilitation, Harvard Medical School, Spaulding Rehabilitation Hospital, Boston, MA, USAThe Heat Distribution Index (HDI) has been used to capture the abnormal variance in knee temperature distribution as a proxy for inflammation in osteoarthritis. HDI has been derived from thermal camera (TC) data, but its use has been limited to static conditions, as TCs are impractical for dynamic assessments. This study evaluates the feasibility of using a wearable array of thermistors to assess HDI changes in response to exercise, using TC data as reference. Ten healthy participants were enrolled, and knee skin temperature was measured pre-, post-exercise, and during a cooldown period of approximately 30 min. The thermistor-based system detected a significant HDI increase post-exercise (<inline-formula> <tex-math notation="LaTeX">$\Delta HDI=0.76^{\circ }\text {C}, p\lt 0.001$ </tex-math></inline-formula>) consistent with the TC results (<inline-formula> <tex-math notation="LaTeX">$\mathrm {\Delta HDI=0.71^{\circ }C, p\lt 0.001)}$ </tex-math></inline-formula>, with no statistical difference detected between the two methods <inline-formula> <tex-math notation="LaTeX">$\mathrm {(p\gt 0.05)}$ </tex-math></inline-formula>. During cooldown, both systems tracked recovery trends without detectable differences <inline-formula> <tex-math notation="LaTeX">$\mathrm {(p\gt 0.05)}$ </tex-math></inline-formula>. The mean HDI error for the thermistor array was 0.20&#x00B1;0.36&#x2218;C. Simulations assessing performance and sources of error showed negligible bias in HDI estimates regardless of the number of thermistors, while variance decreased as thermistor count increased. A more uniform sensor distribution across the region of interest improved accuracy over clustering near its edges, while misplacement had minimal impact except for rare outliers. These findings support the feasibility of a wearable array of thermistors for assessing exercise-induced HDI changes. Improvements in sensor placement to maximize skin contact while allowing for perspiration may enhance reliability. This work lays the foundation for real-time thermal monitoring and may aid in developing wearable tools to monitor patients with knee osteoarthritis.https://ieeexplore.ieee.org/document/11043146/Digital healthheat distribution indexinflammationknee osteoarthritisthermistor arraywearable sensors
spellingShingle Benito L. Pugliese
Virginia Civeriati
Adam S. Tenforde
Danilo Demarchi
Paolo Bonato
Detecting Exercise-Induced Temperature Distribution Changes at the Knee Using a Wearable Array of Thermistors
IEEE Access
Digital health
heat distribution index
inflammation
knee osteoarthritis
thermistor array
wearable sensors
title Detecting Exercise-Induced Temperature Distribution Changes at the Knee Using a Wearable Array of Thermistors
title_full Detecting Exercise-Induced Temperature Distribution Changes at the Knee Using a Wearable Array of Thermistors
title_fullStr Detecting Exercise-Induced Temperature Distribution Changes at the Knee Using a Wearable Array of Thermistors
title_full_unstemmed Detecting Exercise-Induced Temperature Distribution Changes at the Knee Using a Wearable Array of Thermistors
title_short Detecting Exercise-Induced Temperature Distribution Changes at the Knee Using a Wearable Array of Thermistors
title_sort detecting exercise induced temperature distribution changes at the knee using a wearable array of thermistors
topic Digital health
heat distribution index
inflammation
knee osteoarthritis
thermistor array
wearable sensors
url https://ieeexplore.ieee.org/document/11043146/
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