Table 4.
Single-muscle fiber size and contractile function in YE, LLE, and OH
| CSA, µm2 | Po, mN | Vo, FL/s | Vmax, FL/s | |
|---|---|---|---|---|
| MHC I fibers | ||||
| YE | 5,178 ± 157 | 0.62 ± 0.02† | 1.10 ± 0.02 | 0.97 ± 0.02 |
| LLE | 4,983 ± 184 | 0.69 ± 0.02 | 1.11 ± 0.02 | 1.01 ± 0.03 |
| OH | 4,902 ± 159 | 0.63 ± 0.02 | 1.09 ± 0.02 | 0.94 ± 0.02 |
| MHC IIa fibers | ||||
| YE | 4,719 ± 164* | 0.75 ± 0.03* | 3.29 ± 0.08 | 3.17 ± 0.08 |
| LLE | 3,253 ± 189 | 0.61 ± 0.03 | 3.71 ± 0.09* | 3.64 ± 0.09* |
| OH | 3,031 ± 153 | 0.56 ± 0.02 | 3.33 ± 0.07 | 3.23 ± 0.07 |
Values are means ± SE. CSA, cross-sectional area; FL, fiber length; LLE, lifelong exercisers; MHC, myosin heavy chain; OH, old healthy nonexercisers; Po, peak force; Vmax, maximal shortening velocity; Vo, unloaded shortening velocity; YE, young exercisers.
*
P < 0.05 vs. other groups;
†
P = 0.056 vs. LLE.