Table 3.
Twitch characteristics of muscle from Fig. 2A
| TTP, ms | +dF/dt, mN·mm−2·s−1 | +dF/dt/F, s−1 | RT50, ms | −dF/dt, mN·mm−2·s−1 | −dF/dt/F, s−1 | |
|---|---|---|---|---|---|---|
| Nonfailing | ||||||
| Lopt | 219.3 ± 15.0 | 109.4 ± 24.7 | 7.0 ± 0.4 | 142.4 ± 11.4 | −100.4 ± 30.1 | −5.5 ± 0.3 |
| L95 | 210.5 ± 15.6 | 81.8 ± 14.4* | 7.6 ± 0.6 | 130.3 ± 10.5 | −72.0 ± 19.3 | −5.8 ± 0.3 |
| L90 | 193.9 ± 13.0*† | 64.0 ± 11.8* | 8.2 ± 0.6* | 126.8 ± 7.8* | −51.0 ± 12.9* | −5.9 ± 0.5 |
| Failing | ||||||
| Lopt | 211.2 ± 13.8 | 104.1 ± 26.3 | 7.6 ± 0.6 | 153.1 ± 9.5 | −70.2 ± 17.7 | −4.9 ± 0.3 |
| L95 | 204.8 ± 15.8 | 71.9 ± 16.3* | 7.6 ± 0.6 | 143.1 ± 8.1 | −46.8 ± 11.5* | −4.8 ± 0.3§ |
| L90 | 195.8 ± 14.4 | 51.9 ± 12.1* | 8.2 ± 0.7* | 140.4 ± 8.6 | −31.5 ± 6.8* | −5.2 ± 0.4 |
All parameters are means ± SE (measured at 0.5 Hz); n = 8 nonfailing, n = 9 failing (1–3 trabeculae/heart). TTP, time to peak force; +dF/dt, maximal velocity of contraction; +dF/dt/F, maximal velocity of contraction normalized to developed force; RT50, time from peak force to 50% relaxation; −dF/dt, maximal velocity of relaxation; −dF/dt/F, maximal velocity of relaxation normalized to developed force; Lopt, optimal length; L95, 95% of Lopt; L90, 90% of Lopt. P < 0.05 as determined with ANOVA for repeated measures with Bonferroni post hoc analysis:
*
vs. Lopt,
†
vs. L95 of the same group.
§
P < 0.05 vs. nonfailing of the same length as determined with unpaired t-test.