▁under we ar , ▁so ▁we aring ▁separate ▁under we ar ▁is ▁not ▁necessary . ▁Poly ester ▁is ▁a ▁common ▁fabric ▁in ▁running ▁short s ▁and ▁makes ▁it ▁comfortable . ▁ ▁Vari ants ▁▁ ▁Many ▁running ▁short s ▁have ▁a ▁se am ▁cut ▁up ▁the ▁side ▁of ▁each ▁leg ▁to ▁enable ▁fre er ▁movement . ▁Man ufact ur ers ▁define ▁running ▁short s ▁according ▁to ▁the ▁length ▁of ▁the ▁leg ▁which ▁is ▁not ▁cut . ▁For ▁example , ▁a ▁ 3 / 4 ▁se am ▁means ▁that ▁ 1 / 4 ▁of ▁the ▁length ▁is ▁cut . ▁▁▁ 1 / 2 ▁split ▁se am ▁short s ▁are ▁the ▁short est . ▁▁ 3 / 4 ▁split ▁se am ▁short s ▁are ▁short , ▁but ▁not ▁as ▁short ▁as ▁ 1 / 2 ▁split ▁se am ▁short s . ▁ ▁Square ▁leg ▁short s ▁have ▁no ▁split ▁at ▁all . ▁ ▁Long er ▁short s ▁are ▁not ▁ideal ▁for ▁running . ▁ ▁A ▁runner ' s ▁st ride ▁may ▁pull ▁up ▁the ▁short s ' ▁fabric , ▁which ▁can ▁cause ▁dis com fort . ▁ ▁Non eth eless , ▁some ▁run ners ▁prefer ▁longer ▁short s ▁because ▁they ▁cover ▁a ▁greater ▁portion ▁of ▁their ▁legs . ▁▁▁ ▁Some ▁run ners ▁use ▁athlet ic ▁hot ▁p ants ▁as ▁running ▁short s . ▁Like ▁ 1 / 2 ▁split ▁se am ▁short s , ▁hot ▁p ants ▁do ▁not ▁enc umber ▁leg ▁movement . ▁ ▁Ly cra ▁running ▁short s ▁are ▁an ▁alternative ▁to ▁conventional ,