Table 2.
Skeletal Muscle Characteristics
| YM (n = 16) |
YW (n = 15) |
OM (n = 20) |
OW (n = 20) |
p Value: Gender | p Value: Age | O versus Y (%) | |
|---|---|---|---|---|---|---|---|
| Voluntary activation (%) | 90.1 ± 3.7 | 92.2 ± 3.8 | 88.5 ± 5.9 | 90.9 ± 5.1 | .073 | .252 | −1 |
| Moment arm (cm) | 4.0 ± 0.2 | 3.3 ± 0.3 | 4.0 ± 0.3 | 3.4 ± 0.3 | <.001 | .447 | 3 |
| R. leg lean mass (kg) | 10.3 ± 1.0 | 6.5 ± 0.8 | 8.8 ± 1.6 | 5.6 ± 0.8 | <.001 | <.001 | −14 |
| R. quads mass (kg) | 2.2 ± 0.3 | 1.4 ± 0.2 | 1.6 ± 0.3 | 1.1 ± 0.2 | <.001 | <.001 | −28 |
| VL fascicle length (mm) | 90.6 ± 11.3 | 86.6 ± 12.0 | 95.0 ± 13.9 | 88.4 ± 10.1 | .073 | .290 | 4 |
| VL pennation angle (deg) | 15.3 ± 2.9 | 13.8 ± 1.8 | 12.3 ± 2.1 | 11.9 ± 1.4 | .061 | <.001 | −17 |
| VL thickness (mm) | 25.2 ± 3.2 | 19.9 ± 2.9 | 20.4 ± 3.5 | 17.9 ± 2.8 | <.001 | <.001 | −15 |
| VI fascicle length (mm) | 100.5 ± 11.0 | 92.5 ± 10.5 | 93.3 ± 12.6 | 87.4 ± 11.2 | .014 | .028 | −6 |
| VI pennation angle (deg) | 12.0 ± 2.5 | 10.9 ± 2.0 | 11.9 ± 2.7 | 10.5 ± 1.7 | .025 | .699 | −2 |
| VI thickness (mm) | 21.1 ± 4.9 | 18.2 ± 4.0 | 19.0 ± 3.1 | 15.9 ± 3.6 | .002 | .026 | −11 |
| RF fascicle length (mm) | 76.7 ± 16.0 | 70.7 ± 10.8 | 78.3 ± 20.0 | 71.9 ± 19.7 | .150 | .738 | 2 |
| RF pennation angle (deg) | 19.2 ± 4.0 | 18.0 ± 2.4 | 15.6 ± 3.1 | 14.9 ± 2.7 | .084 | <.001 | −20 |
| RF thickness (mm) | 23.6 ± 4.2 | 19.9 ± 4.0 | 20.4 ± 4.3 | 17.8 ± 5.0 | .005 | .015 | −12 |
| VM fascicle length (mm) | 94.7 ± 13.1 | 74.1 ± 15.9 | 87.5 ± 12.0 | 74.9 ± 17.7 | <.001 | .375 | −4 |
| VM pennation angle (deg) | 20.8 ± 4.3 | 19.5 ± 7.2 | 19.6 ± 3.2 | 15.3 ± 2.7 | .011 | .014 | −13 |
| VM thickness (mm) | 31.3 ± 5.1 | 21.5 ± 3.4 | 26.6 ± 4.2 | 19.3 ± 4.8 | <.001 | .002 | −13 |
| Type I FCSA (µm2) | 4,880 ± 690 | 4,180 ± 920 | 5,230 ± 1,940 | 4,160 ± 1,190 | .708 | .487 | 4 |
| Type II FCSA (µm2) | 6,110 ± 1,330 | 4,600 ± 650 | 5,000 ± 1,440 | 2,960 ± 500 | <.001 | <.001 | −26 |
Note: Data shown as mean ± SD. FCSA = fiber cross-sectional area (available from 13 young men, 8 young women, 20 older men, and 10 older women); OM = older men; OW = older women; RF = rectus femoris; VL = vastus lateralis; VI = vastus intermedius; VM = vastus medialis; YM = young men; YW = young women.