Table 2.
Effects of age and sex on mechanical and neural factors
| Young | Older | Main effect | Interaction effect | |||||
|---|---|---|---|---|---|---|---|---|
| Age | Sex | |||||||
| Male (n = 11) | Female (n = 13) | Male (n = 11) | Female (n = 9) | Diff %, p value | Diff %, p value | Age × sex p value |
||
| Muscle Strength and RTD | KE MVIC (Nm) | 317.9 ± 73.3 | 179.6 ± 52.2 | 167.2 ± 38.7 | 124.7 ± 31.8 | 39.1, <0.001 | 35.2, <0.001 | <0.01 |
| KF MVIC (Nm) | 176.0 ± 53.0 | 96.0 ± 28.0 | 82.6 ± 20.9 | 55.1 ± 11.1 | 47.1, <0.001 | 38.7, <0.001 | <0.05 | |
| RTD (Nm/s) | 1044.7 ± 252.0 | 592.6 ± 185.5 | 413.2 ± 190.0 | 391.1 ± 136.3 | 49.6, <0.001 | 30.1, <0.001 | <0.01 | |
| Tissue stiffness | MAS (N/m) | 1281.7 ± 403.4 | 796.4 ± 609.4 | 605.2 ± 213.8 | 485.5 ± 144.3 | 45.9, <0.001 | 29.1, <0.05 | 0.150 |
| MS (N/m) | 488.7 ± 50.2 | 416.7 ± 52.4 | 466.6 ± 39.7 | 394.2 ± 37.4 | 3.5, 0.115 | 14.7, <0.001 | 0.989 | |
| MA of VL | Muscle thickness (mm) | 24.6 ± 3.4 | 21.6 ± 2.7 | 20.3 ± 2.1 | 18.6 ± 1.5 | 15.1, <0.001 | 9.1, <0.01 | 0.397 |
| Lf (mm) | 105.1 ± 10.8 | 104.2 ± 7.1 | 88.1 ± 10.1 | 91.9 ± 11.1 | 14.1, <0.001 | −2.6, 0.683 | 0.533 | |
| Ɵ (°) | 13.5 ± 2.9 | 11.8 ± 1.9 | 13.1 ± 1.7 | 11.1 ± 1.4 | 3.0, 0.392 | 13.7, <0.01 | 0.847 | |
| Surface EMG | VL activation (mV) | 0.214 ± 0.063 | 0.160 ± 0.049 | 0.158 ± 0.073 | 0.119 ± 0.063 | 24.1, <0.05 | 22.8, <0.05 | 0.677 |
| BF co-activation (%) | 18.0 ± 10.2 | 25.9 ± 9.4 | 16.2 ± 10.7 | 20.4 ± 8.5 | 19.0, 0.223 | −38.3, < 0.05 | 0.567 | |
| MDF (Hz) | 65.6 ± 10.3 | 62.4 ± 9.0 | 58.6 ± 10.9 | 54.1 ± 7.2 | 11.4, <0.05 | 5.0, 0.193 | 0.815 | |
Values are mean ± SD
KE knee extensors, KF knee flexors, MVIC maximal voluntary isometric contraction, RTD rate of torque development, MAS musculo-articular stiffness, MS muscle stiffness, MA muscle architecture, Lf fascicle length, Ɵ pennation angle, VL vastus lateralis, BF biceps femoris, MDF median frequency