A new method to calculate external mechanical work using force-platform data in ecological situations in humans: Application to Parkinson's disease

Background and aim: To accurately quantify the cost of physical activity and to evaluate the different components of energy expenditure in humans, it is necessary to evaluate external mechanical work (W-EXT). Large platform systems surpass other currently used techniques. Here, we describe a calculation method for force-platforms to calculate long-term W-EXT. Methods: Each force-platform (2.46 x 1.60 m and 3.80 x 2.48 m) rests on 4 piezoelectric sensors. During long periods of recording, a drift in the speed of displacement of the center of mass (necessary to calculateW(EXT)) is generated. To suppress this drift, wavelet decomposition is used to low-pass filter the source signal. By using wavelet decomposition coefficients, the source signal can be recovered. To check the validity of W-EXT calculations after signal processing, an oscillating pendulum system was first used; then, 10 healthy subjects performed a standardized exercise (squatting exercise). A medical application is also reported in eight Parkinsonian patients during the timed ``get-up and go'' test and compared with the same test in ten healthy subjects. Results: Values of W-EXT with the oscillating pendulum showed that the system was accurate and reliable. During the squatting exercise, the average measured W-EXT was 0.4% lower than theoretical work. W-EXT and mechanical work efficiency during the ``get-up and go'' test in Parkinson's disease patients in comparison with that of healthy subjects were very coherent. Conclusions: This method has numerous applications for studying physical activity and mechanical work efficiency in physiological and pathological conditions. (C) 2016 Elsevier B.V. All rights reserved.