WHICH IS THE BEST WAY TO PERFORM THE PHYSIOLOGICAL COST INDEX IN ACTIVE INDIVIDUALS WITH UNILATERAL TRANS-TIBIAL AMPUTATION?
Authors: Brunelli Stefano , Sancesario Andrea , Iosa Marco , Delussu Anna Sofia , Gentileschi Noemi , Bonanni Cinzia , Foti Calogero , Traballesi Marco 
Published: December 2019

BACKGROUND: Physiological Cost Index (PCI) is a simple method used to estimate energy expenditure during walking. It is based on a ratio between heart rate and self-selected walking speed. Previous studies reported that PCI is reliable in individuals with lower limb amputation but only if there is an important walking impairment. No previous studies have investigated the correlation of PCI with the Energy Cost Walking (ECW) in active individuals with traumatic unilateral trans-tibial amputation, considering that this particular category of amputees has an ECW quite similar to healthy individual without lower limb amputation. Moreover, it is important to determine if PCI is also correlated to ECW in the treadmill test so as to have an alternative to over-ground test.
OBJECTIVES: The aim of this study was to evaluate the correlation between PCI and ECW in active individuals with traumatic trans-tibial amputation in different walking conditions. The secondary aim was to evaluate if this correlation permits to determine ECW from PCI values.
METHODOLOGY: Ninety traumatic amputees were enrolled. Metabolic data, heart rate and walking speed for the calculation of ECW and for PCI were computed over-ground and on a treadmill with 0% and 12% slopes during a 6-minute walking test.
FINDINGS: There is a significant correlation between ECW and PCI walking over-ground (p=0.003; R2=0.10) and on treadmill with 12% slopes (p=0.001; R2=0.11) but there is only a poor to moderate correlation around the trendline. No significant correlation was found walking on treadmill with 0% slope. The Bland-Altman plot analysis suggests that is not possible to evaluate ECW directly from PCI.
CONCLUSIONS: PCI is a reliable alternative measure of energy expenditure during walking in active individuals with trans-tibial amputation when performing over-ground or at high intensity effort on treadmill. PCI is therefore useful only for monitoring a within subject assessment.
LAYMAN’S ABSTRACT
The knowledge of the energy cost of walking in disabled people is important to improve strategies of rehabilitation or fitness training and to develop new prosthetic and orthotic components. The “gold standard” for the evaluation of the energy cost of walking is the oxygen consumption measurement with a metabolimeter, but the testing procedure is expensive and time consuming, hardly practicable in many rehabilitation centers. The Physiological Cost Index (PCI) is an indirect tool that evaluates the oxygen consumption during walking. PCI considers heart rate during walking, in relation to the speed, as an indicator of energy expenditure. The formula is “walking heart rate – resting heart rate /speed”. PCI is widely used in literature but there is not a solid evidence of a direct correlation between PCI and energy cost of walking. In particular, for individuals with unilateral trans-tibial amputation without comorbidities, no previous studies have been conducted about this correlation. It has to be noticed that individuals with unilateral trans-tibial amputation have an energy cost of walking quite similar to healthy people. Previous studies reported that in healthy people such correlation does not exist. For this reason, the aim of this study was to evaluate if and in which walking condition a linear correlation exists between PCI and Energy Cost Walking in individuals with unilateral trans-tibial amputation. Oxygen consumption measurement with a metabolimeter and PCI were computed over-ground and on a treadmill with 0% and 12% slopes during a 6-minute walking test in 90 participants. We have found that PCI is an alternative measure of energy cost of walking when performing over-ground or with high intensity effort on treadmill (12% slope). These findings could be useful when PCI is used for monitoring a fitness training or for evaluation tests.
Article PDF Link: https://jps.library.utoronto.ca/index.php/cpoj/article/view/32953/25717
How to Cite: Brunelli S, Sancesario A, Iosa M, Delussu A.S, Gentileschi N, Bonanni C, Foti C, Traballesi M. Which is the best way to perform the Physiological Cost Index in active individuals with unilateral trans-tibial amputation? Canadian Prosthetics & Orthotics Journal. Volume2, Issue1, No.5, 2019. https://doi.org/10.33137/cpoj.v2i1.32953.
CORRESPONDING AUTHOR:
Dr. Stefano Brunelli,Fondazione Santa Lucia, IRCCS, Via Ardeatina 306, 00179 Rome, Italy.ORCID: https://orcid.org/0000-0002-5986-1564Tel. +39 0651501844; Fax +39 0651501919E-MAIL: s.brunelli@hsantalucia.it