Yellow Stripe on backs of Aussie beach volleyballers?

[Lion1]

As I was watching a beach volleyball game, I noticed that the Australian women players had a yellow stripe going vertically down their backs. I don't know much about this sport. Can anyone tell me the purpose of this stripe?

 

[beakumhawks]

Clearly they are cowards.

 

[Jaker]

Does it extend down to the crack of their ass?

 

[Lion1]

My question is a serious one. I sincerely wanted a logical answer, not wisecracks from comedians who aren't funny.

 

[beakumhawks]

^^ Well, what did you really expect? Smartass remarks that aren't funny are my specialties.

 

[Bryan Lord]

Clearly they are cowards.

This.

 

[pacific 44]

The swimmers have green stripes running every which way.