Sensitivity analysis and comparison of two methods of using heart rate to represent energy expenditure during walking

BACKGROUND: Heart rate is an accurate and easy to use method to represent the energy expenditure during walking, based on physiological cost index (PCI). However, in some conditions the heart rate during walking does not reach to a steady state. Therefore, it is not possible to determine the energy expenditure by use of the PCI index. The total heart beat index (THBI) is a new method to solve the aforementioned problem. OBJECTIVE: The aim of this research project was to find the sensitivity of both the physiological cost index (PCI) and total heart beat index (THBI). METHOD: Fifteen normal subjects and ten patients with flatfoot disorder and twosubjects with spinal cord injury were recruited in this research project. The PCI and THBI indexes were determined by use of heart beats with respect to walking speed and total distance walked, respectively. RESULTS: The sensitivity of PCI was more than that of THBI index in the three groups of subjects. CONCLUSION: Although the PCI and THBI indexes are easy to use and reliable parameters to represent the energy expenditure during walking, their sensitivity is not high to detect the influence of some orthotic interventions, such as use of insoles or using shoes on energy expenditure during walking.