Anyone know why only 11 spikes are allowed in USATF XC cross country events? Why not 10? 12? It seems an odd number would make sense for reasons of symmetry - I can't think of why 11 is the number.
Rule 3(b):
The sole and the heel of the shoes shall be so constructed as to provide for
the use of up to 11 spikes. Any number of spikes up to 11 may be used,
but the number of spike positions shall not exceed 11.
NOTE: For Youth Athletics exception, see Rule 302.5(g).