Question

why don't Spikes make athletes run slower as they increase friction....and friction slows down objects

Answer 1

yes your thinking is absolutely correct but think once again......if the athlete will wear a spikeless shoes and run very fast then there will be very high chances that his leg will slip.....so to reduce shoe to slip during race.....spike shoes are manufactured.......

Answer 2

Friction and velocity have no connection what do ever. Friction increased as the normal force on the object increased. Many would know it as a reaction force.So if we apply force on the sliding block perpendicular to it's direction of motion, friction will increase.

Athletes respond the same to increasing the stiffness of the spike plate. Some barely got better and some got slower, but most improved their speed.

Hope this helps you...