I just got excited with this old paper by Eva Andersson and my graphic designs (not really) with Adobe Illustrator. Below are some graphics that explain the muscle activation workings of the hip flexors during running. Figure 1 shows muscle activation and hip range of motion during running at 4 metres per second (about a 20:50 5km run). Please note, raw EMG does not look like my blue scribbles - it is just a schematic so back off.
Figure 2 shows when all of the hip flexors are active during the running gait cycle. (more…)