Table 3.
Twitch properties and metabolic variables from 2-Hz protocol
| Young | Older | 95% CI | P | |
|---|---|---|---|---|
| Force | ||||
| Average twitch force, N | 23 ± 9 | 22 ± 7 | −8, 8 | 0.940 |
| Average twitch FTI, Ns | 2.5 ± 1.2 | 2.9 ± 1.1 | −0.8, 1.6 | 0.504 |
| Metabolism | ||||
| pH end-exercise | 6.96 ± 0.03 | 7.04 ± 0.04 | 0.03, 0.12 | 0.001 |
| PCr onset λ, s−1 | 0.023 ± 0.005 | 0.020 ± 0.007 | −0.009, 0.004 | 0.430 |
| [PCr]SS, mM | 23.9 ± 2.9 | 26.5 ± 2.7 | −0.19, 5.4 | 0.065 |
| Δ[PCr], mM | 15.6 ± 2.6 | 13.1 ± 2.5 | −5.0, −0.14 | 0.062 |
| Twitch cost, mM·Twitch−1 | 0.180 ± 0.06 | 0.131 ± 0.04 | −0.097, −0.001 | 0.045 |
Values are mean ± SD, and 95% confidence intervals for the difference between groups are presented. Twitch force and force·time integrals (FTI) are averages from entire 2-Hz protocol; PCr onset λ (rate constant for fall in PCr), [PCr]SS (steady-state PCr concentration achieved during twitch contractions), and Δ[PCr] (amplitude of the fall in PCr during twitch contractions) from monoexponential fit of the PCr during 2 Hz protocol.