Table 3. Within-session reliability for PF and selected RFD across age categories.
| Variable |
Day |
Mean ±
SD |
ICC (95%
CI) |
ICC Interpretation |
CV (%)
(95% CI) |
SEM (95%
CI) |
| PF
(All) |
1 |
1722.1
± 716.1 |
0.97 (0.96-0.98) |
Excellent |
4.6 (3.8-5.3) |
17.94 (16.15-19.74) |
| 2 |
1891.3
± 706.7 |
0.98 (0.97-0.99) |
Excellent |
4.3 (3.5-5.1) |
12.46 (11.21-13.70) |
| 3 |
1856.9
± 730.3 |
0.97 (0.95-0.98) |
Excellent |
4.9 (3.9-5.9) |
22.97 (20.67-25.26) |
| RFD50
(All) |
1 |
1952.7
± 2171.9 |
0.74 (0.63-0.82) |
Moderate |
53.4 (47.5-59.3) |
562.18
(505.96-618.39) |
| 2 |
2455.0
± 2039.2 |
0.55 (0.39-0.68) |
Moderate |
49.6 (42.3-57.0) |
921.58
(829.42-1013.73) |
| 3 |
2714.5
± 2162.0 |
0.35 (0.18-0.53) |
Poor |
49.1 (41.8-56.4) |
1403.20
(1262.88-1543.52) |
| RFD250
(All) |
1 |
2551.8
± 1441.3 |
0.85 (0.78-0.90) |
Good |
19.4 (15.3-23.4) |
218.14
(196.33-239.96) |
| 2 |
3075.9
± 1551.8 |
0.86 (0.78-0.91) |
Good |
17.4 (13.2-21.7) |
221.53
(199.37-243.68) |
| 3 |
3131.0
± 1469.4 |
0.90 (0.85-0.94) |
Excellent |
14.5 (11.3-17.6) |
140.38
(126.34-154.42) |
| PF
(U12) |
1 |
946.2 ±
176.5 |
0.96 (0.90-0.98) |
Excellent |
3.5 (2.3-4.7) |
7.65 (6.88-8.41) |
| 2 |
1056.0
± 191.7 |
0.85 (0.69-0.95) |
Good |
5.4 (2.6-8.2) |
27.73 (24.96-30.51) |
| 3 |
994.7 ±
159.4 |
0.91 (0.79-0.97) |
Excellent |
4.2 (2.7-5.8) |
14.24 (12.82-15.67) |
| RFD50
(U12) |
1 |
1088.9
± 673.8 |
0.41 (0.13-0.69) |
Poor |
45.2 (36.9-53.5) |
394.38
(354.94-433.82) |
| 2 |
1381.8
± 895.1 |
0.38 (0.06-0.70) |
Poor |
46.3 (30.6-62.1) |
551.17
(496.05-606.29) |
| 3 |
1429.3
± 868.9 |
0.15 (0.00-0.53) |
Poor |
53.9 (38.9-68.9) |
730.37
(657.33-803.41) |
| RFD250
(U12) |
1 |
1298.0
± 510.4 |
0.75 (0.53-0.88) |
Moderate |
18.0 (9.3-26.8) |
128.49
(115.64-141.34) |
| 2 |
1726.2
± 544.2 |
0.55 (0.23-0.80) |
Moderate |
17.7 (7.0-28.4) |
242.08
(217.88-266.29) |
| 3 |
1591.7
± 540.6 |
0.65 (0.35-0.86) |
Moderate |
20.5 (11.4-29.5) |
187.04
(168.34-205.75) |
| PF
(U15) |
1 |
1788.4
± 430.6 |
0.93 (0.87-0.96) |
Excellent |
4.7 (3.5-6.0) |
29.71 (26.74-32.68) |
| 2 |
1941.7
± 504.9 |
0.98 (0.96-0.99) |
Excellent |
3.4 (2.7-4.1) |
11.68 (10.51-12.85) |
| 3 |
1875.5
± 501.6 |
0.95 (0.90-0.98) |
Excellent |
5.2 (3.8-6.6) |
27.25 (24.53-29.98) |
| RFD50
(U15) |
1 |
1624.4
± 1417.3 |
0.49 (0.26-0.70) |
Poor |
59.7 (51.1-68.3) |
718.45
(646.61-790.30) |
| 2 |
2462.0
± 1790.3 |
0.40 (0.15-0.63) |
Poor |
51.7 (41.1-62.4) |
1069.01
(962.11-1175.91) |
| 3 |
3107.3
± 2260.6 |
0.31 (0.08-0.59) |
Poor |
44.5 (34.5-54.4) |
1570.90
(1413.81-1727.99) |
| RFD250
(U15) |
1 |
2491.3
± 931.3 |
0.60 (0.39-0.77) |
Moderate |
20.6 (14.6-26.6) |
368.73
(331.85-405.60) |
| 2 |
2954.5
± 1129.4 |
0.69 (0.50-0.83) |
Moderate |
18.6 (12.5-24.6) |
345.41
(310.87-379.95) |
| 3 |
3186.7
± 1081.9 |
0.84 (0.70-0.92) |
Good |
11.9 (7.9-15.8) |
175.49
(157.94-193.04) |
| PF
(U18) |
1 |
2591.7
± 472.1 |
0.87 (0.73-0.95) |
Good |
5.6 (3.8-7.4) |
59.23 (53.31-65.15) |
| 2 |
2632.8
± 403.3 |
0.89 (0.75-0.96) |
Good |
5.0 (4.0-6.0) |
44.26 (39.83-48.69) |
| 3 |
2626.8
± 427.3 |
0.80 (0.59-0.92) |
Good |
5.2 (2.5-7.9) |
83.31 (74.97-91.64) |
| RFD50
(U18) |
1 |
3696.3
± 3381.2 |
0.75 (0.50-0.90) |
Moderate |
51.7 (35.2-68.1) |
846.19
(761.57-930.81) |
| 2 |
3515.4
± 2679.1 |
0.54 (0.22-0.79) |
Moderate |
49.0 (32.2-65.8) |
1209.39
(1088.45-1330.33) |
| 3 |
3262.5
± 2381.9 |
0.22 (0.00-0.58) |
Poor |
52.2 (34.5-70.0) |
1846.93
(1662.24-2031.62) |
| RFD250
(U18) |
1 |
4280.6
± 1322.5 |
0.66 (0.37-0.86) |
Moderate |
18.8 (10.5-27.0) |
441.83
(397.65-486.01) |
| 2 |
4651.2
± 1525.7 |
0.80 (0.58-0.92) |
Good |
15.1 (7.1-23.1) |
310.25
(279.22-341.27) |
| 3 |
4468.7
± 1241.8 |
0.78 (0.54-0.91) |
Good |
13.2 (8.2-18.1) |
269.80
(242.82-296.78) |
PF = peak force; RFD = rate of force development; SD = standard deviation; ICC = intraclass correlation coefficient; CI = confidence interval; CV = coefficient of variation; SEM = standard error of measurement.
