Modern sport shoes, and especially football shoes, very often have a stiff sole structure. The synthetic and sometimes carbon material used have clear advantages for performance: they are lightweight and have a good energy absorption-restitution ratio, which is useful for overall performance in sprinting, cutting, or change of direction actions. Lighter, stiffer, better. But this stiffness also means the shoes are more difficult to bend and require a more torque output from the metatarsophalangeal and ankle joints, and in turn, a greater force output from the calf and the intrinsic foot muscles.
Due to the CoviD19 global lockdown, it is very likely that most football players (but also other high-level athletes using typically stiff shoes everyday like sprinters, jumpers, basketball players, rugby players, cyclists) have used their sport-specific shoes less often during this time. Also, they might have maintained a good level of fitness activity, but in sports shoes that are likely much more compliant. One of the possible negative consequences is that at the return to training and performance to their favorite sport (and with the sport-specific shoes conditions), some players may be at greater risk of suffering from soft tissue injury due to a major increase of the mechanical load faced by these tissues. Muscles, fascias, tendons, aponeuroses within the foot, and calf may be directly affected by unusual levels of mechanical strain after 8-10 weeks in « soft » shoes. The most recent injuries reported in some elite players in Spain and Germany tend to show unusual calf injuries… In this video, Pr Morin offers more details about this issue as well as some advice for the players who are in the return-to-performance process, for a gradual increase in this « shoe-specific » loading of the foot and lower leg structures. For those players who may be still locked down and in case of any other future lockdown periods, another advice is given: make sure to wear your sport-specific shoes (and use your sport-specific material) every day or every other day, to make some basic moves (jumps, cuts, shuffles) allowing your system to maintain a regular level of the specific stimulus with these high performance but also high demanding modern shoes.