Table 1.
Mechanical and structural parameters collected in experiments with the RAPID detector
| A RAPID | Rest | T0 | V0,start | V0,T0 |
|---|---|---|---|---|
| SM3 (nm) | 14.34 | 14.56 | 14.31 | 14.48 |
| SM6 (nm) | 7.17 | 7.28 | 7.19 | 7.24 |
| IM3 | 1.37 (0.6) | 1 | — | 0.23 |
| IM6 | 2.68 (1.1) | 1 | — | 0.73 |
| wM3 | 0.5 | 1 | — | — |
| wM6 | 0.4 | 1 | — | — |
| B RAPID | t1/2,force (ms) | t1/2,wM3 (ms) | t1/2,SM3 (ms) | t1/2,SM6 (ms) |
|---|---|---|---|---|
| Isometric | 41.4 ± 13.1 | 26.8 ± 4.2 | 31.3 ± 1.6 | 20.0 ± 3.5 |
| V0,start | 55.2 ± 15.6 | 40.0 ± 4.2 | 42.2 ± 1.4 | 32.3 ± 3.5 |
| Smoothed isometric | — | — | 30.9 ± 1.4 | 20.3 ± 2.1 |
| Smoothed V0 | — | — | 42.2 ± 1.3 | 32.3 ± 2.7 |
A, spacing, intensity and cross-meridional width of M3 and M6 reflections at rest, at the isometric tetanus plateau (T0) and during steady shortening at V0 imposed either 5 ms after the start of stimulation (V0,start) or at the tetanus plateau (V0,T0). X-ray data from eight fibres; V0,start and V0,T0 values are the average of the last two frames before the end of shortening. V0 in these fibres was 1.65 ± 0.30 μm s−1 (half-sarcomere)−1. IM3 and IM6 values inside the brackets are intensity values corrected for the cross-meridional width. B, half-times of change in force (t1/2,force), cross-meridional width of the M3 reflection (t1/2,wM3), spacing of M3 (t1/2,SM3) and spacing of M6 (t1/2,SM6) in the isometric tetanus (first row) and in the tetanus with shortening at V0 imposed 5 ms after the start of stimulation (second row). The third and fourth rows report the time course of M3 and M6 spacings after two time-frame smoothing. The half-time of force is the mean ±s.d. of n = 8 fibres. The error for width and the spacing is provided by the sigmoid fitting program.