Background and objective: According to the assertion made about the damaging role of running shoes as one of the 11 causes of injury seen in every 1000 hours of training, The purpose of this study was to compare the time domain variables of ground reaction force during the stance phase of running using unstable and ordinary shoes.
Method: 20 active females ran in two conditions using an ordinary shoe with a flat sole and an unstable shoe with a rounded sole. The peak values of the ground reaction forces and their related time to peak, free moment peak, impulse, instantaneous and average loading rates were collected and evaluated using a force Plate at a sampling rate of 1000 Hz during stance phase of running. Paired t-test and Wilcoxon test were used to compare the dependent variables between the two conditions (p≤0/05).
Results: Time to peak of vertical passive force and braking force and free moment peak were significantly lower in unstable shoe condition in compared to the ordinary shoe condition while lateral force peak and instantaneous and average loading rates were significantly higher in unstable shoe condition in compared to the ordinary shoe condition (p≤0.05).
Conclusion: According to the findings of the research, since unstable shoes decrease vertical passive force peak time and increase vertical loading rates and create more shock-related running injuries, it does not seem that using these types of shoes have an advantage for runners in preventing or treating injuries.