Analysis Of Variability In Ground Reaction Forces And Electromyography For Runners Of Different Ability

Measures of movement variability have been linked to task performance, adaptability, and injury risk. Further understanding variability in running could help explain training adaptations and injury risks of the sport. This study investigated the variability of vertical, antero-posterior, and medio-lateral ground reaction forces and muscle activity of the medial gastrocnemius (Gn), tibialis anterior (TA), rectus femoris (RF), and biceps femoris (BF) between experienced runners (EXP), recreational runners (REC), and non-runners (NON) at different speeds. It was hypothesized that running experience would affect the amount of variability in all ground reaction force (GRF) components and muscle activation at different speeds. This effect between group and speed did not reach significance for any variables. All groups had less variability as speed increased for all GRF components. This was also true for pre-contact activation of the Gn. Aside from the BF, we found that EXP and REC runners did not have different variability for GRF or electromyography (EMG) measures. Unexpectedly, the pre-contact variability of the RF increased with speed. This highlights the complex nature of EMG variability during running. Though we found consistent variability trends for ground reaction forces, the interactions between EMG variability with speed and group appear to be more complex.