SIGNAL PROCESSING - Biomechanics and Motor Control of Human Movement - page 42

MOMENT OF FORCE (WP30A vs NORMALS)

1

SUPPORT

0

1

HIP

0

− 1

1

KNEE

0

− 1

NORMALS (N = 29)

2

Std.Dev.
WP30A

1

ANKLE

0

% OF STRIDE

Figure 2.20 Moment-of-force profiles of an above-knee amputee (dashed lines) over-
laid on the ensemble-averaged profiles for 29 young adults. The averaged profiles are
solid lines with dotted lines representing one standard deviation. To reduce the vari-

ability of these intersubject moment curves, the joint moments were divided by body
mass prior to averaging. (Reproduced with permission from Winter, D.A. Biomechanics
and Motor Control of Human Gait: Normal, Elderly and Pathological, 2 nd

±

Ed . Waterloo

Biomechanics, 1995.)

lines representing ± one standard deviation. The units of these intersubject
moment-of-force curves are N.m/kg; dividing by body mass was necessary to
decrease the variability by about 50%. Also noted is that the cyclical period
of one stride has been normalized to 100%. Thus, the process to create these
averaged waveforms requires the time base of each subject's profiles to be
altered from their individual stride time (in sec) to a 100% stride baseline.

2.3.2 Normalization of Time Bases to 100%
Assume that for one subject there are n samples of a given variable x over
the stride period and we wish to normalize this time-domain record to N