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Designers have come up with a running shoe for women which adapts shape to suit their hormone levels.
The trainers - available in white, gold and black - capitalise on research showing that changes in levels of oestrogen affect flexibility and the height of the foot's arch.
When oestrogen is high, and a woman is at her most fertile, the arch drops. Later in the month, when she is menstruating, levels of the hormone are low but her arch is raised.