Table 3.
Retest reliability of measuring hip extensor muscle strength in different testing positions in young people with cerebral palsy (n = 19 left hips)
| Position | Mean test score (SD) | Mean retest score ± (SD) | ICC(2,1) | 95% CI of ICC | Mean difference | SD difference | 95% CI of unit of measurement | % change > error | ||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Lower | Upper | Group mean | Individual | Group mean | Individual | |||||||
| Standing | Trial 1 | 10.5 (5.6) | 11.6 (6.3) | .64 | .28 | .84 | 1.1 | 5.07 | -1.32 to 3.57 | -9.53 to 11.78 | 34.9% | 113.1% |
| Mean (trials 1&2) | 10.9 (5.8) | 12.9 (8.2) | .63 | .28 | .84 | 2.0 | 5.92 | -0.72 to 4.99 | -10.31 to 14.58 | 46.8% | 134.8% | |
| Mean (trials 2&3) | 11.7 (6.5) | 13.0 (7.9) | .75 | .47 | .89 | 1.3 | 5.09 | -1.08 to 3.83 | -9.33 to 12.07 | 33.0% | 104.0% | |
| Mean (trials 1-3) | 11.3 (6.2) | 12.5 (7.3) | .72 | .42 | .88 | 1.2 | 5.00 | -1.12 to 3.70 | -9.23 to 11.80 | 33.6% | 105.3% | |
| Maximum | 12.6 (6.8) | 13.9 (8.0) | .73 | .43 | .89 | 1.3 | 5.43 | -1.28 to 3.95 | -10.07 to 12.74 | 32.0% | 101.5% | |
| Prone | Trial 1 | 12.6 (7.4) | 13.7 (8.7) | .83 | .61 | .93 | 1.0 | 4.70 | -1.20 to 3.47 | -8.74 to 11.01 | 28.3% | 88.4% |
| Mean (trials 1&2) | 12.9 (7.5) | 13.5 (8.9) | .83 | .60 | .93 | 0.6 | 4.95 | -1.89 to 3.04 | -9.83 to 10.98 | 24.2% | 85.8% | |
| Mean (trials 2&3) | 13.7 (8.0) | 14.3 (8.8) | .75 | .44 | .90 | 0.6 | 6.08 | -2.38 to 3.67 | -12.13 to 13.42 | 27.6% | 99.0% | |
| Mean (trials 1-3) | 12.6 (8.1) | 13.6 (8.9) | .79 | .54 | .91 | 1.0 | 5.56 | -1.69 to 3.68 | -10.69 to 12.69 | 30.6% | 101.5% | |
| Maximum | 14.6 (8.3) | 14.7 (9.7) | .80 | .53 | .92 | 0.1 | 5.90 | -2.82 to 3.05 | -12.28 to 12.57 | 21.5% | 86.3% | |
| Supine | Trial 1 | 13.8 (6.7) | 13.8 (6.9) | .55 | .13 | .80 | 0.0 | 6.52 | -3.14 to 3.14 | -13.70 to 13.70 | 23.6% | 100% |
| Mean (trials 1&2) | 15.3 (8.2) | 13.7 (6.5) | .62 | .26 | .83 | -1.6 | 6.34 | -4.71 to 1.44 | -15.04 to 11.77 | 10.0% | 77.2% | |
| Mean (trials 2&3) | 15.7 (7.3) | 13.9 (6.9) | .74 | .45 | .89 | -1.8 | 4.94 | -4.16 to 0.60 | -12.15 to 8.59 | 4.3% | 55.0% | |
| Mean (trials 1-3) | 15.1 (6.7) | 13.9 (6.8) | .75 | .46 | .89 | -1.2 | 4.78 | -3.46 to 1.15 | -11.20 to 8.89 | 8.1% | 59.4% | |
| Maximum | 17.1 (7.7) | 15.7 (7.9) | .78 | .53 | .91 | -1.4 | 5.11 | -3.87 to 1.05 | -12.15 to 9.33 | 6.6% | 54.8% | |
NB: Mean difference equals retest minus test strength score. Strength recorded in kilograms. SD, standard deviation; ICC, intraclass correlation coefficient; 95% CI of ICC, 95% confidence interval of ICC; 95% CI of units of measurement, 95% confidence interval of unit of measurement; % change > error, percentage of change required to be 95% confident the change is greater than error