Long-term Exercises on Sand Improved Frequency Spectrum of Lower Limb Muscles During Running in Runners With Over-pronated Feet

Pronated feet (PF) are associated with biomechanical changes during running. It seems that sand training can be a suitable intervention for rehabilitation in individuals with over-pronated feet. This study aims to investigate the effect of long-term exercises on the sand on the frequency of lower limb muscles during running in runners with over-pronated feet.

The current study was a quasi-experimental type. A total of 29 controls with a mean age of 22.2±2.5 years (control group [CG]) and 30 pronated feet (PF) individuals with a mean age of 22.2±1.9 years (intervention group [IG]) participated in this study. In both pre and post-test phases, participants run barefoot on an 18-m runway at a constant velocity of 3.3±5% m/s while EMG activity was recorded using an EMG system. The sand training includes barefoot running for 3 sessions per week for 8 weeks. The frequency of lower limb muscle activities was used as a dependent variable. Repeated-measures analysis of variance (ANOVA) test was used for statistical analysis.

The results demonstrated a significant group×time interaction for gluteus medius (gluteus-M) frequency content at the mid-stance phase (P<0.001; η2=0.670). The results demonstrated an increase of frequency content for gluteus-M in CG (but not in IG) at post-test compared to the pre-test. The results demonstrated a significant group×time interaction for medial gastrocnemius (Gas-M) frequency content at push-off phase (P=0.049; η2 =0.298). Post-hoc analysis demonstrated an increase of Gas-M frequency content in IG (but not in the CG) at the post-test compared to the pre-test. 

As mentioned in a previous study, the reduction of gluteus-M frequency content in IG may be associated with reduced foot pronation after sand training. A higher Gas-M frequency content in the IG after training may lead to improved force generation during the push-off phase.