## 4 Discussion  
The aim of this study was to analyse the changes produced using MS on plantar pressure during a prolonged running, as well as their interaction with the time and foot strike patterns. In this sense, there are few studies that analyse the effect of MS on plantar pressure, and most of these studies do not consider the foot strike pattern (FF, MF, RF), not knowing whether the differences found are associated with the footwear type, foot strike pattern during running or the interaction of both [8; 9; 29; 30; 31; 32; 38; 45]. The results of this study do not show a main effect of the footwear type on the variables analysed, contrary to the results obtained in previous studies, where higher plantar pressure values were obtained with MS vs. CS [9; 29; 36; 46]. In this sense, although several studies relate the increase in pressure to a rapid or inadequate transition to this type of footwear [9; 30; 45], all participants in this study were runners with previous experience in MS, and the factor of previous experience/transition to MS may be the reason for the increased pressure in these studies. However, the results did show significant differences in terms of the shoe*foot strike pattern interaction, specifically in the use of MS in relation to the forefoot vs. midfoot/reaffoot pattern. Thus, higher mean and peak pressure values were observed for forefoot pattern compared to midfoot and rearfoot (Figure 1). In this sense, [PERSON] et al. [37] also obtained higher peak pressure values with MS as well as the study of [PERSON] et al. [45] in non-heeler vs. heeler runners, which could be due to an increase in plantar flexion, a decrease in the contact area, as well as due to the lack of cushioning elements/materials in this type of footwear [5; 8; 13; 31; 39]. In terms of contact area and contact time, the shoe*foot strike pattern interaction reveals that in MS, forefoot runners show less contact time and contact area compared to midfoot/reaffoot runners (Figure 1). Thus, in relation to the contact area, and considering exclusively the footwear type, the results are in line with [PERSON] et al. [38], who observed a decrease in the contact area in the forefoot and midfoot area when analysing barefoot running vs. CS. However, if the foot strike pattern is considered, our results are contrary to those obtained by these authors, as they observed a decrease in this in rearfoot runners in the barefoot condition, probably due to the absence of any type of sport shoes that suppose a small protection. Although it is true that no comparison was made between CS and MS, these results suggest that the decrease in the contact surface with the use of MS may be due to the smaller sole size [46; 47]. Nevertheless, future research considering the sole dimension of the MS with respect to the CS will be necessary to know the effect of the change in the contact area. Regarding the shorter contact times found with MS with a forefoot stride pattern, [PERSON] et al. [36] explain how the reduction in contact time with MS may be an adaptive mechanism to try to attenuate the high loads and pressures that occur with this type of footwear. As discussed above, in our study an increase in mean and peak pressure was observed with a forefoot vs. midfoot/reaffoot running pattern, and it was in this same stride pattern that a reduction in contact time was also found, reinforcing the results of [PERSON] et al. [36]. Another aspect to take into account, as other authors have considered [48; 49; 50], is that the midsole of CS needs time to deform during the step, causing an increase in contact time the thicker the shoe midsole is. Probably the adaptive mechanism to decrease loads in MS and the reduction in the thickness of the sole, together with the reduction in the contact area that occurs in forefoot runners, were the main factors that justifies this reduction in contact time.