Kirsty Chong launched her Australian underwear label, Modibodi, in 2013 as alternative to disposable tampons and pads.

She spent two years fine-tuning the brand’s period-proof design with textile engineers and fibre companies in Australia and the US. The result is a fabric made up of moisture-wicking, antimicrobial, breathable fibres that have made Modibodi one of the world’s top period-proof underwear brands.

After undies came leak-proof swimwear, and sports leggings. The brand’s latest release is a pair of black running shorts ($59), for workouts any time of month. It’ll save a trip to the shops for a new box of tampons not just this month, but for many months to come.

“I’m an avid runner and suffering from bladder leaks while training for a marathon was the catalyst for launching Modibodi in the first place,” Chong says.

“Most women tend to bleed more during the first couple of days of their period – this can be the most uncomfortable time for doing any kind of physical activity. But there’s evidence that working out during this time [can be particularly beneficial]. So I set about designing absorbent, leak-proof running shorts that can be worn without underwear and that work as a total replacement to disposable hygiene on light to moderate [flow] days, to help women feel confident, dry and protected while working out.”

The slim-fit shorts are comfy and lightweight. They’re made with a merino wool outer, and built-in underwear made out of Modibodi’s patented breathable, moisture-wicking, leak-proof fabric, with a three-millimetre thick, stain-resistant liner. Plus, the shorts have a hidden zip pocket for small items such as a key, cash or credit card.

They took 18 months to come to life, from conception to manufacture.

“The fabric was specifically sourced for this product,” Chong says. “It was important that the product felt and performed like a true running short, but offered the same period- and pee-proof protection that our customers have come to expect.”

While the underwear line features four absorbency options ranging from superlight to heavy-overnight, the new shorts are for use on light- or moderate-flow days (up to 10 millilitres, or two tampons worth), though on heavier days they’re a handy reinforcement. And the sweat absorption makes them a great workout option any day of the month.

“I’ve always loved to run,” Chong says. “It’s my way of reducing day-to-day stress and taking some time for myself – which with four kids can be a challenge. I wear these shorts every time I go running, even when I’m not on my period, just in case of little leaks along the way.”

They’re also a sustainable option since they can be kept for years. “They’re safe, they’re durable, they’re hygienic, they’re easy to use … You put them in with your normal wash and hang to dry,” Chong says.

Modibodi offers new customers a 30-day trial – if you’re not a fan, you can get a full refund on one piece (excluding postage).

You can buy the shorts online, and they’re delivered in compostable bags made from biodegradable materials.

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