Article

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 (WEXT).
Large platform systems
surpass other currently used techniques. Here, we describe a calculation method
for force-platforms to calculate long-term WEXT. METHODS: Each force-platform
(2.46x1.60m and 3.80x2.48m) rests on 4 piezoelectric sensors. During long periods
of recording, a drift in the speed of displacement of the center of mass
(necessary to calculate WEXT) 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 WEXT 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 WEXT with the oscillating
pendulum showed that the system was accurate and reliable. During the squatting
exercise, the average measured WEXT was 0.4% lower than theoretical work. WEXT
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.
CI - Copyright (c) 2016 Elsevier B.V. All rights reserved.

Langue : ANGLAIS