The idiomatic English phrase “back foot” refers to a defensive or even losing position. Someone who is “on the back foot” is on the defense, in a disadvantaged position, or defending a territory. This phrase seems to have come from a sports analogy, although opinions differ on its actual origin.
Many who use this phrase consider it to have come from the sport of boxing. In boxing, fighters who are on the back foot are in a defensive position. The physics of this positioning have to do with the way that the lower body and upper body coordinate for defensive guarding and offensive attacking, for example, a fighter plants a foot forward to implement an aggressive punch, exactly opposite to the position being described here.
In British society, many people understand the phrase “on the back foot” as referring to cricket, a popular national sport. Experts point out that in cricket, a player may be on the back foot while protecting a territory. Some British speakers also explain this phrase as being related to contact sports like rugby.
Others see the phrase as pertaining to soccer, or "football" as it is called elsewhere. In this sport, the idiom may refer to the defense of action intended to keep the ball away from the opposition. In both soccer and boxing, one could use the word “backpedaling” to describe a similar defensive procedure.
Over time, the phrase has gone from being literally applied to sports and physical contests, to being something used for any kind of more abstract competition. One prime example is in business, where the party might be described as being “on the back foot” if it is engaged in a losing price war with a competitor, behind in product development, or losing market share. Business leaders may be also use this phrase if they feel they are unable to predict sales numbers, plan for future operations, or leverage existing capital.
Some speakers can use the phrase “back foot” in various ways. For instance, someone could say “I was on my back foot” to describe a personal challenge. Likewise, this phrase can also be applied to a third person in a similar context. Others might substitute different idioms to express the same idea, for example, saying someone was “on the ropes” as a losing participant in a conflict. This phrase has to do with the demarcations of an arena for both boxing and televised wrestling.