Cardiovascular Reactivity (CVR) During Repetitive Work in the Presence of Fatigue

Diogo Carvalho, Luís Silva, Miguel Carvalho, Mariana Dias, Nélson Costa, Duarte Folgado, Maria Lua Nunes, Hugo Gamboa, Kristīne Andža, Elazer Edelman

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Fatigue during repetitive tasks in the workplace has been intrinsically connected with occupational risk and a reduction in productivity. Currently, the measures taken are based on subjective interpretations of fatigue by the workers or on direct muscular activity, which then make up for a cumulative evaluation of fatigue. The concept of “Industry 4.0” wearable devices would allow a continuous monitoring and thus, a more realistic representation of their fatigue levels.Aim: To quantify heart rate variability, measuring cardiovascular responsiveness, during repetitive work when fatigue is present. Tasks: A protocol was developed to simulate a real-life workplace scenario with a set of low-intensity repetitive tasks that are commonly practiced. The signals obtained were then processed, and heart rate variability was calculated using fractal analysis and time domain variables. Hypothesis: It was hypothesized that 1) the amount of variability and 2) the structure of variability will change during repetitive work in the presence of fatigue.Methodology: Participants were asked to perform three 10-minute trials of a repetitive task. Between each trial, a muscular fatigue protocol was carried out, targeting the main agonist muscle. An ECG was collected during the trials (Baseline, Fatigue 1, and Fatigue 2) through a wearable band placed on the level of the xiphoid appendix. Results: The nonlinearity of the heart rate variability showed no statistically significant changes, unlike the time domain measures that significantly differentiated the baseline trial from the fatigue trials, namely the Standard Deviation of NN intervals, the Root Mean Square of successive RR interval differences, Coefficient of Variation, and Heart Rate itself. Conclusions: These results are enthusiastic for applying algorithms that use heart rate variability to quantify cardiovascular responsiveness to fatigue during repetitive work. They show that with information in the time domain, it is possible to verify physiological changes that the worker is undergoing. Additionally, these changes are also related to the amount of variability and not to the fractal structure of heart rate variability.
Original languageEnglish
Title of host publicationIntelligent Human Systems Integration (IHSI 2023)
Subtitle of host publication Integrating People and Intelligent Systems
EditorsTareq Ahram, Waldemar Karwowski, Pepetto Di Bucchianico, Redha Taiar, Luca Casarotto, Pietro Costa
ISBN (Electronic)978-1-958651-45-2
Publication statusPublished - 2023
Event6th International Conference on Intelligent Human Systems Integration: Integrating People and Intelligent Systems - Venice, Italy
Duration: 23 Feb 202324 Feb 2023

Publication series

NameAHFE International
ISSN (Print)2771-0718


Conference6th International Conference on Intelligent Human Systems Integration
Abbreviated titleIHSI 2023


  • ECG
  • Fatigue
  • Heart rate variability
  • Occupational risk
  • Work
  • Industry 4.0
  • Operator 4.0

Field of Science*

  • 3.3 Health sciences

Publication Type*

  • 3.2. Articles or chapters in other proceedings other than those included in 3.1., with an ISBN or ISSN code


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