spikes increase the friction with the ground hence reduces slipping on the ground..therefore a better a grip for the sportsmen and he is able to move faster n safer.
sportsmen uses shoes with spikes as they need to run very fast and skid in the field spikes helps them to run fast
spikes also provide better grip on the ground thereby increasing the friction between the irregularities
shoes with spikes offer more friction because of more irregularities in the surface. This gives better grip to sportsmen while running.