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Fatollahi A, Jafarnezhadgero A A, Sheikhalizade H. The Effect of Sand Exercise Program on Knee Muscle Co-contraction in Runners With Over-pronated Feet During Running. PTJ 2023; 13 (4) :215-224
URL: http://ptj.uswr.ac.ir/article-1-582-fa.html

Purpose: Over-pronated foot (OPF) is a common abnormality of the foot. Sand can change lower limb muscle activities. Therefore, the aim of this study was to evaluate the effect of a sand exercise program on knee muscle co-contraction in runners with OPF.
Methods: Thirty individuals (age range: 18–26 years) with OPF were randomly allocated to the equally sized control and experimental groups. The experimental group performed a sand running exercise protocol for eight weeks. Muscle activities were recorded using an electromyography system. Two variables, including directed co-contraction and general co-contraction, were calculated before and after training programs. 
Results: In the experimental group, lower directed vastus lateralis/vastus medialis co-contraction, greater general knee co-contraction, and directed medial/lateral knee co-contraction during the mid-stance and push-off phases were found at the post-test compared to the pre-test (P<0.017). Irrespective of the time, greater directed medial/lateral knee co-contraction during the push-off phase was observed in the experimental group (P=0.043). 
Conclusion: Sand can be used as a suitable surface for training, as increased muscle co-activation is required to make postural adjustments during running.