View Full Version : Summary: Error Magnitudes

Howard P. Davis
12-01-1998, 07:14 AM
Summary Error Magnitudes:
I want to thank those who responded to my question. I received a number of requests for a summary which indicated to me that my question was at least shared by others. As I indicated when I posed the question there seems to be a large body of literature dealing with specific sources of error but few sources that integrate that information into a uncertainty for the whole process. There are however some good sources of information.

Anthropometry : I did not get any responses to this portion to the question but was able to dig up the following references:

Kouchi, M. et al. (1996) Random errors in anthropometry. J. Human Ergol. 25:155-166.

This is a good reference. It reports a large number of anthropometric measures with their technical error of measurements.

Anthropometric Standardization Reference Manual. Eds( Lohman, Roche and Martorell) Human Kinetic Books, Champaign, Ill.

This is the standard reference on the subject.

Inverse Dynamics Error:

The reference that most closely matched my question was an abstract:
Davis, B.L., Uncertainty in calculating joint moments during gait, Presented at VIII meetings of ESB, Rome June 21-24, 1979.

The paper calculated the effects of measurement uncertainties on joint moment values. Stance phase uncertainties were 7.1, 10.9 and 13.3 Nm for ankle, knee, and hip. It was not reported what the peak torques were so the uncertainties as a percent of signal are not known. Most of the uncertainty was due to joint axes error. An excellent complementary reference is:

Holden, J.P and Stanhope S.J. (1998), The effect of variation in knee center location estimates on net knee joint moments.

Of interest in the above reference is the fact the joint axis location errors are independent of signal size. Therefore small knee torques have a larger proportion of error. If you assume that the gait analyzed in Brian Davis' paper was walking where peak torques on the order of 100 Nm can be expected, uncertainties of 13% at the hip would be in the ball park.

Errors due to surface marker movement (I'm glad I wasn't a subject for these):

Holden, J.P. et al. (1997) Surface movement errors in shank kinematics and knee kinetics during gait. Gait and Posture 5:217-227.

Lafortune M.A. et al. (1992) Three dimensional kinematics of the human knee during walking. J. Biom. 25:347-357.

Cappozzo A., Catani F., and Leardini A.(1993) Skin movement artifacts in human movement photogrammetry. In: Abstracts of the XIVth Congress of the ISB, Paris 1993; 238-239.

Neptune R.R. and Hull M.L. (1995) Accuracy assessment of methods for determining hip movement is seated cycling. J. Biom 28:423-437.

Errors due to mismatch of Force Plate and Camera coordinate systems:
McCaw S.T. and DeVita P. (1995) Errors in alignment of center of pressure and foot coordinates affect predicted lower extremity torques. J Biom. 28:985-988.

Errors due to differentiation and optimization approaches:
There are many papers that apply here. A current trend is to add additional constraints to the model and use optimization techniques to get better estimates as a way around the differentiation problem. Another trend is to add accelerometry to avoid the differentiation. Some of the many references are:

Giakis and Baltzopoulos V (1998) The effects of noise and filtering on the calculation of net joint dynamics of lower segments during walking. Presented at the 11th ESB Conference, Toulouse France, 8-11 July. J. of Biom 31, Supp1 1. P150.

Kuo A.D. (1998). A least-squares estimation approach to improving the precision of inverse dynamics computations. J of Biom. Eng. 120(1):148-159.

Koopman, B., Grootenboer, H.J. and Henk J. (1995) An inverse dynamics model for the analysis reconstruction and prediction of bipedal walking. J. of Biom. 28(11):1369-1376.

Runge, et al. (1995) Estimating net joint torques from kinesiological data using optimal linear system theory. IEEE Trans on Biomed Eng. 42(12):1158-1164.

Cheze L., Fregly, B.J. and Dimnet J. (1995) A solidification procedure to facilitate kinematic analyses based on video system data. J. Biom 28(7):879-884.

Happee R. (1994). Inverse dynamic optimizaiton including muscular dynamics, a new simulatio method applied to goal directed movements. J. of Biom 27(7):953-960.

Ladin, Z. and Wu, G. (1991) Combing position and acceleration measurements for joint force estimation. J of Biom. 24(12):1173-1187.

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