In-shoe plantar pressure distribution and lower extremity muscle activity patterns of backward compared to forward running on a treadmill

- Plantar pressures and EMG patterns were compared in backward and forward running.
- Backward running caused higher loads under the medial forefoot and midfoot.
- Backward running showed a specific toe-heel-toe ground contact pattern.
- Backward running evoked specific EMG patterns in some lower extremity muscles.
- Backward running biomechanics have relevance in sports and rehabilitation.

ObjectiveBackward locomotion in humans occurs during leisure, rehabilitation, and competitive sports. Little is known about its general biomechanical characteristics and how it affects lower extremity loading as well as muscle coordination. Thus, the purpose of this research was to analyze in-shoe plantar pressure patterns and lower extremity muscle activity patterns for backward compared to forward running.MethodsOn a treadmill, nineteen runners performed forward running at their individually preferred speed, followed by backward running at 70% of their self-selected forward speed. In-shoe plantar pressures of nine foot regions and muscular activity of nine lower extremity muscles were recorded simultaneously over a one-minute interval. Backward and forward running variables were averaged over the accumulated steps and compared with Wilcoxon-signed rank tests (p < .05).ResultsFor backward compared to forward running, in-shoe plantar pressure distribution showed a load increase under metatarsal heads I and II, as well as under the medial midfoot. This was indicated by higher maximum forces and peak pressures, and by longer contact times. Muscle activity showed significantly higher mean amplitudes during backward running in the semitendinosus, rectus femoris, vastus lateralis, and gluteus medius during stance, and in the rectus femoris during swing phase, while significantly lower mean amplitudes were observed in the tibialis anterior during swing phase.ConclusionObservations indicate plantar foot loading and muscle activity characteristics that are specific for the running direction. Thus, backward running may be used on purpose for certain rehabilitation tasks, aiming to strengthen respective lower extremity muscles. Furthermore, the findings are relevant for sport specific backward locomotion training. Finally, results provide an initial baseline for innovative athletic footwear development aiming to increase comfort and performance during backward running.

In-shoe plantar pressure distribution patterns of backward (above) and forward (below) treadmill running of a selected participant's left foot during a 1 min measurement indicate the different roll-over processes for both movements which result also in shorter gait lines in backward running.235