Table 1.
Main results for the Pro-Flex and Vari-Flex feet at a treadmill speed of 1.1 m/s across downhill (−7.5°), level (0°), and uphill (+7.5°) terrains.
| Variable | Foot | Terrain | Effect of terrain | Effect of foot | Interaction effect | ||
|---|---|---|---|---|---|---|---|
| Down | Level | Up | |||||
| Peak dorsiflexion angle (deg) | Pro-Flex* | 15.9 ± 2.1 | 18.8 ± 2.7 | 20 ± 2.3 | F = 5.896 | F = 45.363 | F = 5.839 |
| p = 0.027 | p = 0.003 | p = 0.027 | |||||
| Vari-Flex | 9.2 ± 2.9 | 10.6 ± 3.2 | 11.1 ± 3.6 | ηp2 = 0.706 | ηp2 = 0.919 | ηp2 = 0.593 | |
| 1 − β = 0.715 | 1 − β = 0.998 | 1 − β = 0.711 | |||||
| Peak plantarflexion angle (deg) | Pro-Flex | 5.8 ± 2.7 | 4.9 ± 1.8 | 2.4 ± 1.3 | F = 14.915 | F = 0.001 | F = 4.534 |
| p = 0.017 | p = 0.991 | p = 0.091 | |||||
| Vari-Flex | 5.1 ± 4.1 | 4.6 ± 3.9 | 3.4 ± 4.3 | ηp2 = 0.789 | ηp2 = 0.001 | ηp2 = 0.531 | |
| 1 − β = 0.830 | 1 − β = 0.050 | 1 − β = 0.405 | |||||
| Range of motion between shank and foot segments (deg) | Pro-Flex* | 21.7 ± 2.7 | 23.7 ± 3.1 | 22.4 ± 2.3 | F = 1.626 | F = 19.315 | F = 0.487 |
| p = 0.255 | p = 0.012 | p = 0.632 | |||||
| Vari-Flex | 14.2 ± 6.6 | 15.2 ± 6 | 14.5 ± 5.8 | ηp2 = 0.289 | ηp2 = 0.828 | ηp2 = 0.109 | |
| 1 − β = 0.249 | 1 − β = 0.900 | 1 − β = 0.105 | |||||
| Energy stored in the prosthetic foot (J/kg) | Pro-Flex* | −0.24 ± 0.05 | −0.23 ± 0.02 | −0.24 ± 0.05 | F = 0.103 | F = 13.130 | F = 0.301 |
| p = 0.903 | p = 0.022 | p = 0.748 | |||||
| Vari-Flex | −0.18 ± 0.03 | −0.18 ± 0.02 | −0.17 ± 0.03 | ηp2 = 0.025 | ηp2 = 0.766 | ηp2 = 0.070 | |
| 1 − β = 0.061 | 1 − β = 0.772 | 1 − β = 0.083 | |||||
| Total energy returned by the prosthetic foot (J/kg) | Pro-Flex* | 0.2±0.09 | 0.16 ± 0.01 | 0.2 ± 0.04 | F = 2.111 | F = 8.298 | F = 0.147 |
| p = 0.184 | p = 0.045 | p = 0.865 | |||||
| Vari-Flex | 0.15 ± 0.01 | 0.11 ± 0.02 | 0.14 ± 0.05 | ηp2 = 0.345 | ηp2 = 0.675 | ηp2 = 0.035 | |
| 1 − β = 0.313 | 1 − β = 0.586 | 1 − β = 0.066 | |||||
| Energy returned by the prosthetic foot during push-off | Pro-Flex* | 0.18 ± 0.08 | 0.16 ± 0.01 | 0.19 ± 0.04 | F = 1.627 | F = 12.877 | F = 0.083 |
| p = 0.255 | p = 0.023 | p = 0.922 | |||||
| Vari-Flex | 0.13 ± 0.03 | 0.1 ± 0.01 | 0.12 ± 0.05 | ηp2 = 0.289 | ηp2 = 0.763 | ηp2 = 0.020 | |
| 1 − β = 0.249 | 1 − β = 0.764 | 1 − β = 0.059 | |||||
| Work ratio of the prosthetic foot (J/J) | Pro-Flex | 0.78 ± 0.22 | 0.71 ± 0.06 | 0.87 ± 0.18 | F = 3.640 | F = 0.355 | F = 0.992 |
| p = 0.075 | p = 0.584 | p = 0.412 | |||||
| Vari-Flex | 0.86 ± 0.16 | 0.60 ± 0.13 | 0.79 ± 0.25 | ηp2 = 0.476 | ηp2 = 0.081 | ηp2 = 0.199 | |
| 1 − β = 0.501 | 1 − β = 0.075 | 1 − β = 0.167 | |||||
| Energy delivered by the foot/ankle during push-off by the sound limb (J/kg) | Pro-Flex | 0.13 ± 0.06† | 0.20 ± 0.06‡ | 0.39 ± 0.09 †,‡ | F = 27.308 | F = 0.784 | F = 0.812 |
| p < 0.001 | p = 0.426 | p = 0.477 | |||||
| Vari-Flex | 0.12 ± 0.04† | 0.17 ± 0.05‡ | 0.4 ± 0.11 †,‡ | ηp2 = 0.872 | ηp2 = 0.164 | ηp2 = 0.169 | |
| 1 − β = 0.999 | 1 − β = 0.107 | 1 − β = 0.144 | |||||
| CoM energy change during collision by the amputated limb (J/kg) | Pro-Flex | −0.11 ± 0.08 | −0.09 ± 0.05 | −0.09 ± 0.06 | F = 0.243 | F = 1.954 | F = 0.212 |
| p = 0.656 | p = 0.235 | p = 0.713 | |||||
| Vari-Flex | −0.10 ± 0.08 | −0.08 ± 0.04 | −0.07 ± 0.04 | ηp2 = 0.057 | ηp2 = 0.328 | ηp2 = 0.050 | |
| 1 − β = 0.068 | 1 − β = 0.192 | 1 − β = 0.067 | |||||
| CoM energy change during propulsion by the amputated limb (J/kg) | Pro-Flex* | 0.10 ± 0.03† | 0.15 ± 0.02‡ | 0.10 ± 0.02†,‡ | F = 5.937 | F = 352.81 | F = 0.137 |
| p = 0.026 | p < 0.001 | p = 0.874 | |||||
| Vari-Flex | 0.07 ± 0.05† | 0.12 ± 0.03‡ | 0.07 ± 0.02†,‡ | ηp2 = 0.597 | ηp2 = 0.989 | ηp2 = 0.033 | |
| 1 − β = 0.718 | 1 − β = 0.999 | 1 − β = 0.065 | |||||
| CoM energy change during collision by the sound limb (J/kg) | Pro-Flex | −0.31 ± 0.1 | −0.14 ± 0.06 | −0.15 ± 0.06 | F = 6.178 | F = 0.663 | F = 0.378 |
| p = 0.065 | p = 0.461 | p = 0.602 | |||||
| Vari-Flex | −0.34 ± 0.17 | −0.14 ± 0.06 | −0.18 ± 0.07 | ηp2 = 0.607 | ηp2 = 0.142 | ηp2 = 0.086 | |
| 1 − β = 0.486 | 1 − β = 0.098 | 1 − β = 0.080 | |||||
| CoM energy change during propulsion by the sound limb (J/kg) | Pro-Flex | 0.09 ± 0.09 | 0.20 ± 0.07 | 0.25 ± 0.06†,‡ | F = 26.529 | F = 3.490 | F = 4.102 |
| p < 0.001 | p = 0.135 | p = 0.059 | |||||
| Vari-Flex | 0.10 ± 0.08 | 0.18 ± 0.06 | 0.29 ± 0.07†,‡ | ηp2 = 0.869 | ηp2 = 0.466 | ηp2 = 0.506 | |
| 1 − β = 0.999 | 1 − β = 0.301 | 1 − β = 0.551 | |||||
| Magnitude of the first peak of the GRF on the sound limb (N/W) | Pro-Flex* | 1.22 ± 0.14 | 0.98 ± 0.09 | 1.05 ± 0.06 | F = 13.116 | F = 7.332 | F = 0.909 |
| p = 0.003 | p = 0.054 | p = 0.441 | |||||
| Vari-Flex | 1.27 ± 0.17 | 1.08 ± 0.06 | 1.08 ± 0.07 | ηp2 = 0.766 | ηp2 = 0.647 | ηp2 = 0.185 | |
| 1 − β = 0.969 | 1 − β = 0.537 | 1 − β = 0.157 | |||||
| Magnitude of the first peak of the knee adduction moment in the sound limb (Nm/kg) | Pro-Flex | 0.5 ± 0.12 | 0.52 ± 0.19 | 0.37 ± 0.17 | F = 3.982 | F = 2.021 | F = 1.235 |
| p = 0.063 | p = 0.341 | p = 0.341 | |||||
| Vari-Flex | 0.52 ± 0.13 | 0.50 ± 0.12 | 0.43 ± 0.17 | ηp2 = 0.499 | ηp2 = 0.236 | ηp2 = 0.236 | |
| 1 − β = 0.539 | 1 − β = 0.197 | 1 − β = 0.198 | |||||
*Significant main effect between prosthetic feet. †Significant difference from the level terrain. ‡Significant difference from the downhill terrain. Note, there are instances in which there was a significant effect of terrain yet the post hoc revealed no differences between terrains. Effect size was estimated using partial eta squared (ηp2). Observed power was calculated as 1 − β.