The Physiological Cost Index in elderly subjects during treadmill and floor walking

Aim: To determine the Physiological Cost Index (PCI) in a sample population of 12 healthy adults aged over 65 years, on a treadmill versus a 10-metre floor track. Method: Subjects were studied on two occasions, one week apart. On each occasion the subjects performed a floor walking test and a treadmill walking test according to a randomized, crossover design. During each trial the subjects' walking speed, resting heart rate and walking heart rate were measured. The PCI (beats/metre) - an empirical measure of the energy efficiency in gait - was calculated from the net heart rate (walking heart rate - resting heart rate {beats/ minute}) divided by the walking speed (metre/minute). Results were expressed as mean ± standard deviation and significance established at p<0.01. Results: There was no significant difference between the mean resting and walking heart rates during treadmill and floor walking. The treadmill walking speed (61.21 ± 19.27 metre/minute) was significantly slower than the floor walking speed (72.17 ± 12.02 metre/minute). Thus the treadmill PCI (0.60 ± 0.26 beats/metre) was significantly higher than the floor walking PCI (0.43 ± 0.13 beats/metre). Clinical relevance: The results of this study suggest that a floor walking track offers a more functional medium than the treadmill for assessing the PCI in elderly subjects.