Underwear to Run In – Runderwear Women’s G string Review

Runderwear G string thong running underwear

For those of you who don’t know, Runderwear was founded in 2013 by Jamie and Richard who met while at university. They started the company as a solution to the problem of chaffing and exploited a gap in the market which Jamie found while attempting to find some performance underwear to complement his technical outer clothing at the New York Marathon Expo.

In 2018 Runderwear won the coveted “Best Underwear & Socks Brand” at the 2018 and 2019 Running Awards as voted by customers. In 2019 they became the Official Underwear and Bra partner of England Athletics.

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Runderwear Running Thong Review

I ordered my Runderwear G string from Amazon (mainly because I wanted the next day delivery from my Prime account in the UK). I paid £17 including delivery for a small pair in blue / cyan.
If you order directly from Rundewear, they’ve often got deals on, including an introductory discount and shipping offers; however, you can also easily get them from Amazon.


Runderwear thong

They turned up promptly, as you’d expect from Amazon. The Runderwear packaging is attractive and well made. I was slightly disappointed from a sustainability perspective to see that inside the recyclable box the underwear was also in a plastic bag.




womens running underwear

When I’d ordered them, there was a negative quality review on Amazon from someone who had purchased a pink pair and found that they had immediately developed holes in the back. I carefully inspected my pair as soon as they arrived and found there to be no signs of holes or fabric weakness in the back. I was slightly concerned to see what appeared to be fabric fraying where the waistband attaches to the main fabric, however, 4 washes in and there has been no change so I am concluding this is nothing to be concerned about.

As promised, what limited seaming that does exist is flat-locked and unobtrusive. All the detail that you’d normally have on the tag is woven into the elastic waistband, doubling the benefits of no chafing from a tag or remnant thereof, and no risk of losing the laundry information by cutting it off!


Ladies running underwear sizes

As mentioned in some reviews, the sizing on these appears to run small. I am normally a UK 6 – 8, albeit with a generous caboose, but the size small UK 8-10 fits me perfectly. I was slightly concerned about how the potential for the thong portion to feel a bit off-putting, as the fabric is a heavier weight than that of the thongs that I have been wearing, but I adjusted to it quickly and soon didn’t notice them at all.


Although designed specifically for running, there isn’t room in my wallet or my life for an almost £20 pair of underwear that can’t multitask – therefore they got immediately got slotted into the normal sport rotation to see how they coped.

Over a period of two weeks, they had five encounters with the washing machine (always at 40 degrees as per the laundry directions), but they did sneak into the tumble drier twice, serves me right for not sorting my laundry prior to washing. I am happy to report they have survived their encounters with the drier so far, and I will be more careful sorting laundry from now on. When I did manage to rescue them from the load before it got to the tumble drier, they were fully dry and ready to go again after 12 hours hanging to dry in my conservatory.

Onto the sports and outcomes involved in my testing:

A vigorous game of squash last approximately an hour, they were paired with a thin pair of women’s Nike Pro leggings with a very shiny finish to check how much VPL they would show and how well the leggings would move over the underwear fabric.

  • As expected, there was VPL through the thin Nike Pros, these are the acid test for VPL and so far nothing has passed. There was a visible fit line where the robust elastic waistband transitioned above to skin and below to underwear fabric, and there was an element of the leggings not sliding as smoothly over the fabric as it does over the skin.
  • Stayed put nicely
  • No chaffing
  • no standard thong discomfort when running about chasing the ball

A long hike in terrible weather, thanks StormCiara

  • Stayed put nicely
  • no chaffing
  • no bunching under multiple layers of hiking clothes and waterproofs
  • stayed nice and dry with the wicking keeping up with both temperature and activity level changes.

The duration test:

Wear all day at work, Run to CrossFit, Olympic lifting class and Run home

  • Felt a bit intrusive when first put on but soon adjusted to them as they were comfortable and supportive at work
  • Didn’t move about during the entire exercise session, despite a very sweaty run (I was almost late for the gym), repeated direction changes from pulling weights off the floor, going into and out squats and then running again.
  • Comfortable for all activities including squats, clean and jerk and snatches – not butt flossing
  • Remained comfortable even with badly fitting running leggings

I chose the thong-style as the first technical underwear to review because I was completely prepared to be disappointed; however, all in all, I found the Runderwear G-String to be a very pleasant surprise. The fit is supportive and mostly invisible, once they’re on they stay put and they kept me a comfortable temperature and any sweat wicked away. I won’t be running out and replacing every pair of underwear I own with the Runderwear G-String, as I found the fabric a bit too thick and the waist elastic too powerful for constant wear, but as an athletic underwear, they have certainly earned their spot in the standard rotation.

Are you convinced to try workout specific or running specific underwear? We love your comments, so you can pick up your own Runderwear Running G-String to try from Amazon and let us know what you think.


After completing this review I was unexpectedly offered the opportunity to hack out (do a trail ride) on a lovely Polo pony. Armed with multiple experiences indicating riding horses in thong underwear is a bad idea, I nevertheless decided that since they were so good in all other sports I tried that I’d give them a whirl here too. I’m delighted to report that we did a 10-mile ride, walking, jogging, trotting, cantering, and galloping, in an English saddle over mixed terrain and I suffered no underwear related discomfort! Chalk up another success for this thong, I think its the most comfortable one I’ve ever worn.

Please note, this page contains affiliate links, our policy on affiliate links can be found here. All reviews are the opinion of the reviewer, and all reviewed products have been purchased for review.

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6 Responses

  1. Gina says:

    PERFECT timing, I was looking at sports bras and underwear only a few days ago! I have never heard of Runderwear, I certainly like the features, simplicity and packaging. What a great success this product has been 😀

    Your website looks great too!

    • Lisa says:

      Thanks Gina! I’ve been thoroughly impressed with Runderwear, the thong I tried has excelled at everything I put to it, even when I thought there was no way it would come through.

  2. Sharon says:

    What a thorough review. I have never heard of this company but I can tell based on the degree of testing you’ve completed on this that it’d be a product I’d trust.

    • Lisa says:

      Thanks Sharon, I have to say testing this pair of underwear was actually a pleasure. Not what I ever expected I’d say about a sports thong!

  3. suzanne says:

    Hi Lisa,
    What a great review. Putting them through all your tests is a great way to show others their quality and durability.
    I’ll show my daughter as she wears thongs and does many physical activities.
    I myself, though, have never tried them and don’t expect I’ll start at 60, lol. Kind of like an all-day wedgie for me, haha.
    Thanks again,

    • Lisa says:

      Hi Suzanne,

      Thanks for your kind comment. You know an all-day wedgie was exactly what I thought I was in for when I first ordered the Runderwear G-String! I’m sure your daughter will find them as comfortable as I do!


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