Introduction
Methods
Participants
Running task
Footwear
Motion analysis
Variable | Definition |
---|---|
Peak KFM (Nm/kg) | Peak external knee flexion moment during stance. Positive values indicate higher KFM. |
Stance time (s) | Time of stance from initial contact (> 20 N) until toe off (< 20 N). |
Sagittal plane knee-GRF lever arm (mm) | Perpendicular distance between GRF and knee joint centre in laboratory sagittal plane. Calculated at time of peak KFM. |
Sagittal plane resultant GRF magnitude (BW) | Resultant magnitude of the sagittal plane GRF calculated at time of peak KFM. Force was converted from Newton’s to bodyweight (BW). |
Knee flexion angle (°) | Sagittal plane knee flexion angle at time of peak KFM. Positive values indicate knee flexion. |
Ankle dorsiflexion angle (°) | Sagittal plane ankle dorsiflexion angle at time of peak KFM. Positive values indicate dorsiflexion. |
Hip flexion angle (°) | Sagittal plane hip flexion angle at time of peak KFM. Positive values indicate hip flexion. |
Knee flexion excursion (°) | Difference between the knee flexion angle at initial contact and peak across stance phase. |
Knee flexion at initial contact (°) | Knee flexion angle at initial contact of force plate. Initial contact designated as time when GRF > 20 N. |
Statistics
Results
Variable | Mean ± SD (n = 60) |
---|---|
Age (years) | 15.6 ± 5.4 |
Weight (kg) | 49.6 ± 13.8 |
Height (m) | 1.6 ± 0.1 |
Estradiol (pmol/L) | 8.1 ± 5.1 |
Thigh segment length (cm) | 41.2 ± 3.5 |
Shank segment length (cm) | 36.8 ± 3.2 |
Differences in peak KFM, GRF and lower limb kinematics between footwear conditions
Variable | Barefoot | Stability | Neutral | P value barefoot v high-support | P value barefoot v low-support | P value high-support v low-support |
---|---|---|---|---|---|---|
Peak KFM (Nm/kg) | 2.24 ± 0.41 | 2.67 ± 0.41a | 2.62 ± 0.39a | < 0.001 | < 0.001 | 0.06 |
Running velocity (m/s) | 3.12 ± 0.20 | 3.12 ± 0.21 | 3.14 ± 0.21 | 0.76 | 0.07 | 0.41 |
Stance time (s) | 0.23 ± 0.03 | 0.25 ± 0.02a | 0.25 ± 0.02a | < 0.001 | < 0.001 | 0.08 |
Sagittal plane knee-GRF lever arm (mm)c | 103.75 ± 18.05 | 119.50 ± 18.04ab | 117.29 ± 17.05a | < 0.001 | < 0.001 | 0.04 |
Sagittal plane resultant GRF magnitude (BW)c | 2.48 ± 0.45 | 2.55 ± 0.44a | 2.56 ± 0.44a | < 0.001 | < 0.001 | 0.27 |
Hip flexion angle (°)c | 37.64 ± 7.60 | 40.45 ± 8.04a | 40.04 ± 7.58a | < 0.001 | < 0.001 | 0.43 |
Knee flexion angle (°)c | 46.96 ± 4.52 | 48.99 ± 4.84a | 49.36 ± 4.10a | < 0.001 | < 0.001 | 0.32 |
Knee flexion at initial contact (°) | 19.11 ± 4.30 | 16.16 ± 4.40ab | 17.64 ± 5.83a | < 0.001 | 0.02 | 0.04 |
Knee flexion excursion (°) | 32.40 ± 4.79 | 36.21 ± 4.22a | 36.31 ± 4.32a | < 0.001 | < 0.001 | 0.77 |
Ankle dorsiflexion angle (°)c | 19.01 ± 3.81 | 20.17 ± 3.08a | 19.75 ± 3.37 | 0.01 | 0.12 | 0.12 |
Predictors underlying change in peak KFM between footwear and barefoot conditions
Predictors | Change in Peak KFM |
---|---|
Fixed effect estimates, (95% CI), p-value | |
Footwear condition | 0.04, (− 0.10, 0.18), p = 0.55 |
Change in sagittal plane knee-GRF lever arm (mm) in barefoot condition | 0.02, (0.02, 0.03), p < 0.001 |
Change in sagittal plane knee-GRF lever arm in footwear condition | 0.02, (0.01, 0.03), p < 0.001 |
Change in sagittal plane resultant GRF magnitude (BW) | −0.01, (− 0.06, 0.04), p = 0.72 |
Change in hip flexion angle (°) | − 0.004, (− 0.02, 0.01), p = 0.46 |
Change in knee flexion angle (°) | 0.01, (− 0.001, 0.03), p = 0.07 |
Change in knee flexion at initial contact (°) | − 0.0003, (− 0.01, 0.01), p = 0.96 |
Change in knee flexion excursion (°) | 0.003, (− 0.01, 0.03), p = 0.64 |
Change in ankle dorsiflexion angle (°) | − 0.0002, (− 0.01, 0.01), p = 0.97 |