The expansive playing field, length of playing time (90 minutes for men, 70 minutes for women) and the relatively rough nature of the game were enough to discourage women's participation. Coupled with the fact that physiologists in Japan say that one soccer match expends as much energy as running a marathon, it is understandable why the game remained initially the domain of men.
足球場地遼闊，比賽時間長（男子九十分鐘，女子七十分鐘），其規則又容許有限度的身體衝撞，賽起球來有點「野蠻」，加上運動量大（據日本運動專家研究，足球的體力消耗量僅次於馬拉松及三萬米長跑），是少數最激烈的運動之一。