TABLE 3.
Motor unit properties at different contraction levels
| Parameter | Sex | Beta | 95%CI | P value |
|---|---|---|---|---|
| MU FR (Hz) | Males | 0.50 | 0.28 to 0.71 | <.001 |
| Females | 0.43 | 0.18 to 0.69 | .001 | |
| MU FR variability (%) | Males | 0.99 | 0.52 to 1.45 | <.001 |
| Females | 1.18 | 0.63 to 1.72 | <.001 | |
| MUP area (μV·ms) | Males | 273.62 | 215.81 to 331.43 | <.001 |
| Females | 199.35 | 148.13 to 250.56 | <.001 | |
| MUP phases | Males | −0.05 | −0.14 to 0.04 | .302 |
| Females | 0.10 | −0.02 to 0.21 | .098 | |
| MUP amplitude (μV) | Males | 188.21 | 153.75 to 222.67 | <.001 |
| Females | 142.40 | 106.27 to 178.53 | <.001 | |
| MUP turns | Males | 0.05 | −0.11 to 0.20 | .565 |
| Females | 0.09 | −0.08 to 0.26 | .316 | |
| MUP duration (ms) | Males | −0.16 | −0.52 to 0.20 | .381 |
| Females | 0.13 | −0.16 to 0.42 | .371 | |
| NFM Jiggle (%) | Males | 3.08 | 2.38 to 3.79 | <.001 |
| Females | 3.08 | 2.34 to 3.82 | <.001 | |
| NFM duration (ms) | Males | −0.40 | −0.54 to −0.26 | <.001 |
| Females | −0.34 | −0.50 to −0.18 | <.001 | |
| NFM Seg Jitter (μs) | Males | 0.77 | −0.37 to 1.91 | .188 |
| Females | 0.51 | −0.85 to 1.87 | .463 | |
| NFM dispersion (ms) | Males | −0.09 | −0.23 to 0.05 | .228 |
| Females | −0.05 | −0.28 to 0.18 | .655 | |
| NFM area (kV/s2) | Males | 0.98 | 0.68 to 1.29 | <.001 |
| Females | 0.72 | 0.39 to 1.05 | <.001 |
Beta value and 95% confidence interval (CI) represent the model predicted change per unit from 10% to 25% maximum voluntary contraction (MVC), shown separately for males and females. All statistical analysis was based on multilevel mixed effect linear regression models with each subject as an independent cluster. The values in bold reflect statistically significant (P < .05) results.
Abbreviations: FR, firing rate; MU, motor unit; MUP, motor unit potential; NFM, near fibre motor unit potential; Seg, segment.