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Correction.


In a research report published in Physical Therapy in 1993, Oatis (1) calculated stiffness stiffness

half way to rigidity, tetany; result of insufficient use of the part.
 and damping damping

In physics, the restraint of vibratory motion, such as mechanical oscillations, noise, and alternating electric currents, by dissipating energy. Unless a child keeps pumping a swing, the back-and-forth motion decreases; damping by the air's friction opposes the
 coefficients of the knee joint, based on the moment of inertia inertia (ĭnûr`shə), in physics, the resistance of a body to any alteration in its state of motion, i.e., the resistance of a body at rest to being set in motion or of a body in motion to any change of speed or change in direction of  of the leg and foot with respect to the center of mass of the leg-foot segment. She alerts Journal readers to an error in those calculations leading to the results presented in Table 3 of the article. Equations 1 and 2 should have used the moment of inertia with respect to the knee.

Oatis reanalyzed and recalculated the stiffness and damping coefficients (shown in Tabs. 1 and 2), using the moments of inertia The following is a list of moments of inertia. Mass moments of inertia have units of dimension mass × length2. It is the rotational analogue to mass. It should not be confused with the second moment of area (area moment of inertia), which is used in bending calculations.  with respect to the knee joint. As in the 1993 study, assessment of stiffness and damping coefficients demonstrated moderate to high reliability, with most intraclass correlation In statistics, the intraclass correlation (or the intraclass correlation coefficient[1]) is a measure of correlation, consistency or conformity for a data set when it has multiple groups.  coefficients (ICCs) greater than .7 and 2 ICCs greater than .59. (2) Oatis found that the revised stiffness and damping coefficients were larger than those reported in the 1993 study.

The original study reported that both stiffness and damping coefficients were increased in the 45-degree test. In the reanalysis, damping coefficients were significantly increased in the test at 45 degrees compared with the test at 75 degrees, whereas the increase in the stiffness coefficients at the 45-degree test position was statistically insignificant. Effects of gender appeared to be similar to those reported in the original study, with increased stiffness and damping coefficients in male subjects at both test positions. Effects of age remain unclear. The 1993 study reported that stiffness at the 75-degree test position was increased in the 30- to 39-year-old group compared with the 70+ age group. The reanalysis also showed a statistically significant increased stiffness in the 30- to 39-year-old subjects compared with the 20- to 29-year-old group. These differences may reflect the significant structural differences in these joints or the differences in data collection, or both. No attempt was made in the reanalysis to identify any structural or functional differences among the different age groups.

References

(1) Oatis CA. The use of a mechanical model to describe the stiffness and damping characteristics of the knee joint in healthy adults. Phys Ther. 1993;73:740-749.

(2) Portney LG, Watkins Watkins may refer to:
  • The town of Watkins, Colorado
  • The city of Watkins, Minnesota
  • Watkins Incorporated, a manufacturer of cosmetics, health remedies and baking products
  • Watkins Electric Music, a manufacturer of musical instruments
 MP. Foundations of Clinical Research: Applications to Practice. 2nd ed. Upper Saddle River Saddle River may refer to:
  • Saddle River, New Jersey, a borough in Bergen County, New Jersey
  • Saddle River (New Jersey), a tributary of the Passaic River in New Jersey
, NJ: Prentice Hall Prentice Hall is a leading educational publisher. It is an imprint of Pearson Education, Inc., based in Upper Saddle River, New Jersey, USA. Prentice Hall publishes print and digital content for the 6-12 and higher education market. History
In 1913, law professor Dr.
 Health; 2000:565.
Table 1.

Stiffness Coefficients (N x m/rad) Calculated from 2 Different Moments
of Inertia: Stiffness Coefficients Calculated Using the Moment of
Inertia With Respect to the Knee Joint (Corrected Values) Are Larger
Than When Calculated Using the Moment of Inertia With Respect to the
Center of Mass (Original Values)

Age Group   Original                      Corrected

(y)         45 [degrees]   75 [degrees]   45 [degrees]   75 [degrees]

20-29
  [bar.X]   3.27           3.14           10.92          9.770 (a)
  SD        1.27           1.12           2.828          2.541
  Range     1.29-5.68      1.03-5.71      8.919-12.92    7.973-11.57
30-39
  [bar.X]   4.30           4.06 (a)       13.13          12.38 (a)
  SD        1.47           1.29           4.793          4.505
  Range     1.70-7.24      2.26-6.33      9.745-16.52    9.196-15.57
40-49
  [bar.X]   3.69           3.49           11.49          10.87
  SD        0.93           0.79           2.885          2.330
  Range     2.13-5.50      1.73-5.21      9.452-13.53    9.222-12.52
50-59
  [bar.X]   3.44           3.21           11.27          10.29
  SD        1.33           0.86           4.607          2.806
  Range     0.62-5.71      1.97-5.04      8.012-14.53    8.308-12.28
60-69
  [bar.X]   3.46           3.22           10.77          10.12
  SD        1.23           1.03           1.916          3.577
  Range     1.39-5.34      1.84-4.91      9.415-12.12    7.587-12.65
70+
  [bar.X]   3.25           2.75 (a)       10.74          9.037 (a)
  SD        1.08           1.13           4.460          3.323
  Range     1.95-4.74      1.23-4.93      7.586-13.89    6.687-11.39

(a) Post hoc Bonferroni method of multiple correlations to examine
effects of age, significant at P<.05.

Table 2.

Damping Coefficients (N x m/rad) Calculated from 2 Different Moments of
Inertia: Damping Coefficients Calculated Using the Moment of Inertia
With Respect to the Knee Joint (Corrected Values) Are Larger Than When
Calculated Using the Moment of Inertia With Respect to the Center of
Mass (Original Values)

Age Group   Original                      Corrected

(Y)         45 [degrees]   75 [degrees]   45 [degrees]    75 [degrees]

20-29
  [bar.X]   0.10           0.07           0.2910          0.2223
  SD        0.03           0.02           0.0834          0.0728
  Range     0.03-0.16      0.03-0.10      0.2320-0.3500   0.1708-0.2738
30-39
  [bar.X]   0.13           0.10           0.3930          0.2996
  SD        0.06           0.06           0.1146          0.1661
  Range     0.04-0.25      0.03-0.26      0.3120-0.4740   0.1821-0.4170
40-49
  [bar.X]   0.11           0.08           0.3388          0.2505
  SD        0.04           0.03           0.0915          0.0861
  Range     0.05-0.17      0.04-0.15      02741-0.4035    0.1897-0.3114
50-59
  [bar.X]   0.11           0.08           0.3807          0.2789
  SD        0.08           0.06           0.2241          0.1369
  Range     0.02-0.34      0.04-0.27      0.2222-0.5392   0.1821-0.3757
60-69
  [bar.X]   0.10           0.09           0.3086          0.2703
  SD        0.05           0.03           0.0133          0.0784
  Range     0.04-0.26      0.04-0.15      0.2992-0.3180   0.2149-0.3258
70+
  [bar.X]   0.08           0.09           0.2566          0.3043
  SD        0.02           0.05           0.0795          0.1659
  Range     0.05-0.11      0.04-0.19      0.2004-0.3128   0.1869-0.4216
COPYRIGHT 2005 American Physical Therapy Association, Inc.
No portion of this article can be reproduced without the express written permission from the copyright holder.
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Publication:Physical Therapy
Article Type:Correction Notice
Date:Dec 1, 2005
Words:920
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