BIOMECHANICAL MOVEMENT SYNERGIES - Biomechanics and Motor Control of Human Movement - page 283

MOMENT of FORCE (natural cadence, n = 9)

2

SUBJECT: WM22

SUPPORT
CV

= 20%

1

TO

0

1 HIP

CV

TO 68%

=

0

− 1

HIP + KNEE

1

CV = 21%

TO

0

− 1

KNEE
CV

1

= 60%

TO

0

− 1

MEAN

TO

=

TOE OFF (forced to 60%)

CV COEFFICIENT of VARIATION

(during STANCE phase)

=

+− 1 STD.DEV.

2

ANKLE
CV = 18%

1

TO

0

0 20 40 60 80 100

% of STRIDE

Figure 11.1 Ensemble averaged moment profiles for repeat trials from the same sub-
ject over 9 days. The support moment, M s = M h + M k + M a with extensor moment at

each joint plotted M k is plotted to demon-

strate the dramatic reduction in variability because of day-to-day trade-offs between
these two joints. See the text for a detailed discussion. (Reproduced with permission
from Winter, D. A. Biomechanics and Motor Control of Human Gait: Normal, Elderly
and Pathological ,2 nd

+ ve. The hip + knee moment, M h + k = M h +

Edition, Waterloo Biomechanics, 1995.)

a covariance analysis. Figure 11.2 presents the variances and covariances for
these repeat day-to-day trials along with 10 repeat trials done on a second
subject done minutes apart. The hip and knee variances and covariances are
related as follows with all units in ( N . m ) 2

σ hk = σ h + σ k − σ h + k (11.1)

where: σ h and σ k = are the mean hip and knee variances over stance.

σ h + k = is the mean variance of the hip + knee profile over

stance.