Research utilized biomechanical methodologies through muscle co-contractions to understand the difference between used and new military boots.
• The results showed the type of military boots affects the general and directional co-contraction of the knee joint during running.
• Increased general knee co-contraction may be associated with instability of the joint after fatigue.

Plain Language Summary 
During daily activities, soldiers are required to engage in strenuous physical activity. Essentially, this will include walking and running carrying various items of equipment often through rough terrain. Level of fitness increases using running activities. On the other hand, co-contraction increment energy expenditure, leading to a high cost of walking and fatigue. Therefore, this study was conducted to examine the effect of three types of military boots mileage on knee muscular co-contraction during running. Fifteen healthy males received three new and used military boots. They were asked to wear these boots for over 6 months. Participants were recruited in May 2022 from Mohaghegh Ardabili University, Ardabil City, Iran. We used the freeware tool GPower to calculate a one-sided a priori power analysis. A wireless EMG system with eight pairs of bipolar Ag/AgCl surface electrodes was used to record the activity of the tibialis anterior (TA), gastrocnemius medialis (Gas-Med), biceps femoris (BF), semitendinosus (ST), vastus lateralis (VL), vastus medialis (VM), and rectus femoris (RF), and gluteus medius (Glut-Med) muscles of the right leg. Pre and postintervention, EMG testing was conducted and co-contraction of the right leg was recorded during running at 3.6 run speed. Based on the results of this study, and following the use of military boots, the knee general co-contraction was increased. The results demonstrated more directed mediolateral knee co-contraction and greater directed flexion and extension co-contraction in used boots situations. Individuals express a clear need to use military boots using for their soldiers to help cope with challenges associated with the use of military boots and their injuries. Changing boots after 6 months of heavy wearing seems to be suitable for military people.

The activity level of both the tibialis anterior and lateral gastrocnemius muscles in adolescent girls with foot pronation can be increased with Kyokushin karate training.
• There was no significant change in the activity level of the fibularis longus muscle in adolescent girls with foot pronation after eight weeks of Kyokushin karate training.
• Kyokushin karate training can improve the height of the medial longitudinal arch in adolescent girls with foot pronation.

Plain Language Summary 
Flat feet is a condition characterized by a reduction in the medial longitudinal arch and is considered an abnormality. It is prevalent in approximately 25% of adults, with a higher incidence in women than men. Kyokushin karate training has been shown to improve the height of the medial longitudinal arch, suggesting it may offer a potential solution for correcting flat feet.