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.
To take advantage of this, Asics’ scientists created trainers with three layers of cushioning below the arch. Closest to the foot is a layer of foam, followed by an air-filled gap and a plastic block.
When the woman’s arch is low, the foam is compressed into the gap and when her arch is high the foam fills out, ensuring her feet are supported whatever the time of the month.
However, the GEL-KAYANO 16 does not come cheap. At £120 a pair they cost almost three times as much as the Japanese brand’s least expensive women’s shoe.