Table 1. Contractile properties of the studied motor units in control and trained animals.
| CT [ms] | HRT [ms] | TwF [mN] | TetF [mN] | Tw/Tet | PTP | FatI | |
|---|---|---|---|---|---|---|---|
| FF | |||||||
| C | 15.8 ± 3.0 | 21.3 ± 3.6 | 114.7 ± 34.7 | 289.0 ± 64.1 | 0.38 ± 0.07 | 1.33 ± 0.19 | 0.20 ± 0.11 |
| 2W | 14.7 ± 2.6 | 19.9 ± 2.9 | 93.9 ± 39.1 * | 243.8 ± 69.5 * | 0.37 ± 0.09 | 1.33 ± 0.19 | 0.23 ± 0.14 |
| 4W | 15.7 ± 3.4 | 21.5 ± 3.7 | 112.4 ± 44.4 | 295.0 ± 85.2 † | 0.37 ± 0.10 | 1.34 ± 0.24 | 0.19 ± 0.10 |
| 8W | 15.3 ± 2.1 | 20.9 ± 2.5 | 96.6 ± 40.2 | 251.5 ± 77.1 | 0.38 ± 0.09 | 1.35 ± 0.24 | 0.22 ± 0.13 |
| FR | |||||||
| C | 16.5 ± 2.6 | 21.7 ± 3.0 | 32.3 ± 20.1 | 119.9 ± 58.4 | 0.25 ± 0.06 | 1.39 ± 0.17 | 0.86 ± 0.12 |
| 2W | 14.9 ± 2.1 * | 19.8 ± 2.5 ** | 27.7 ± 17.7 | 121.6 ± 56.5 | 0.21 ± 0.06 ** | 1.39 ± 0.23 | 0.93 ± 0.09 ** |
| 4W | 14.5 ± 2.7 ** | 19.1 ± 3.1 *** | 26.4 ± 17.0 | 122.4 ± 56.0 | 0.20 ± 0.07 *** | 1.43 ± 0.26 | 0.93 ± 0.10 * |
| 8W | 14.7 ± 2.4 ** | 19.8 ± 2.7 ** | 25.5 ± 19.1 | 134.0 ± 68.9 | 0.18 ± 0.05 ***†† | 1.36 ± 0.19 | 0.94 ± 0.09 ** |
| S | |||||||
| C | 26.2 ± 4.5 | 29.9 ± 4.1 | 5.0 ± 1.9 | 39.3 ± 14.7 | 0.13 ± 0.05 | 0.97 ± 0.09 | 0.98 ± 0.05 |
| 2W | 24.0 ± 3.2 | 27.4 ± 4.1 | 4.3 ± 1.6 | 36.3 ± 13.0 | 0.12 ± 0.02 | 0.98 ± 0.11 | 0.99 ± 0.04 |
| 4W | 26.9 ± 5.5 | 31.5 ± 4.8 | 4.3 ± 2.0 | 35.3 ± 10.8 | 0.12 ± 0.04 | 0.94 ± 0.09 | 0.99 ± 0.03 |
| 8W | 27.1 ± 5.9 | 29.6 ± 4.9 | 3.6 ± 1.3 | 36.3 ± 8.2 | 0.10 ± 0.02 **§ | 0.94 ± 0.11 | 1.00 ± 0.04 |
The mean values of the studied properties (± SD) of fast fatigable (FF), fast fatigue resistant (FR) and slow (S) motor units (MUs) in the control (C) group and the three trained groups, consisting of rats trained for 2 weeks (2W), 4 weeks (4W) and 8 weeks (8W).
CT, the contraction time; HRT, the half-relaxation time; TwF, the twitch force; TetF, the maximal tetanic force; Tw/Tet, the twitch-to-tetanus ratio; PTP, the post-tetanic potentiation; FatI, the fatigue index.
Statistical significance in comparison to the control (C) group is represented by * p < 0.05, ** p < 0.01, *** p < 0.001.
Statistical significance in comparison to the group trained for 2 weeks (2W) is represented by † p < 0.05, †† p < 0.01.
Statistical significance in comparison to the group trained for 4 weeks (4W) is represented by § p < 0.05 (Dunn’s post hoc test) (S1 File).