Dear all,
Theo asked
>OK, point taken. How do you define LOADING RATE?
>
Loading rate of force (or pressure) is the velocity with which force (or
pressure) is building up.
For example, if force is increasing from 0 Newton to 100Newton within 100
millisecond of time, the loading rate will be 100 Newton/0.1 second=
1000N/sec. This is of course the AVERAGE loading rate for that time
interval. It's like calculating the average speed when driving 100 km in
two hours, resulting in an average of 50km/hour)
If the velocity is not constant over a larger period of time but instead is
varying all the time, we could be interested in the INSTANTANUOUS velocity
or loading rate at a specific moment in time. Calculating the instantaneous
velocity or loading rate however, is somewhat more complicated and
requires knowledge of calculus. But a good approximation can be reached by
using the same calculation method as above for calculating the average,
but reducing the time interval to a very small time lapse. If at a certain
moment during heel impact, force changes from 50 N within 1/1000 of a
second, 50N/(1/1000s)= 50000N/s will be a good approximation of the
INSTANTANUOUS loading rate of force at that instant of time.
GRAPHICALLY, the instantaneous loading rate corresponds to the INCLINATION
of the TANGENT of the force or pressure curve at a certain moment of time.
The steeper this tangent, the higher the respective velocity or loading
rate.
Most of the time one is only interesting in the MAXIMAL loading rate, this
the loading rate at the steepest point of the curve. As the force or
pressure curves during heel impact are steeper than during forefoot
loading, loading rate at the heel is mostly higher than at the forefoot
Hope this helps. Feel free to ask if more question arise.
Regards to all,
Bart
*******************************************************************
Bart Van Gheluwe
Laboratory of Biomechanics
Vrije Universiteit Brussel -Fac. LK
Vakgroep BIOM
Pleinlaan 2, 1050 Brussel, Belgium
Tel.: 02/629.27.33 (31)
Fax: 02/629.27.36
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