Getting back into a gym routine after summer always sounds simple enough.
You find your trainers, dig out your favourite leggings, promise yourself you’re actually going to use that gym membership this time… and then halfway through your first workout, you remember all the little things that make exercise uncomfortable.
Leggings slipping down. Sports bras digging in. Underwear riding up.
The last one is particularly annoying because it’s something you shouldn’t really have to think about while you’re working out.
Whether you’re heading back to strength training, joining a September fitness class or simply trying to move a little more each week, the best underwear for exercise should make your workout more comfortable, not become another distraction.
Here’s what to look for when choosing gym underwear – and why longer-leg bamboo boxers can make a surprisingly good addition to your workout drawer.
Why regular underwear can fall short during workouts
Your everyday underwear might be perfectly comfortable when you’re sitting at a desk or walking around the house.
Add squats, lunges, cycling, incline walking or an hour-long gym class, however, and things can change pretty quickly.
Exercise means more movement, more friction and usually more sweat. Underwear that felt fine when you got dressed can suddenly start:
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Riding up
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Digging into your waist
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Bunching beneath leggings
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Holding moisture against your skin
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Rubbing between your thighs
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Needing constant adjustment
And once you notice uncomfortable underwear during a workout, it’s very difficult to stop noticing it.
That’s why what you wear to the gym underneath your clothes deserves almost as much attention as the leggings or shorts you put over the top.
The goal isn’t complicated: you want underwear that stays where you put it.
What should you actually look for in gym underwear?
You don’t necessarily need underwear covered in complicated technical claims to exercise comfortably.
For most regular gym sessions, there are a few things that matter far more.
Breathability
Sweating is completely normal when you exercise.
Your underwear therefore needs to allow heat and moisture to move rather than making everything feel hot and clammy.
This becomes especially important if you’re exercising several times a week. Breathable fabric can simply feel much more pleasant against your skin during and after a workout.
A fit that moves with you
Think about how much movement happens during even a fairly relaxed gym session.
You might squat, stretch, bend, walk, cycle or lift weights within the same hour.
Your underwear needs enough stretch to move with your body without becoming restrictive.
At the same time, something too loose can bunch beneath your clothing.
The sweet spot is a close but comfortable fit that moves with you rather than against you.
No ride-up
Nobody wants to stop halfway through a squat because their underwear has disappeared somewhere it definitely wasn’t five minutes earlier.
A leg that stays in place can make a huge difference.
Flissie boxer shorts are available with both a 6-inch and 9-inch leg, giving you more coverage than traditional briefs or very short boy shorts.
If thigh friction tends to be a problem when you exercise, that extra fabric also creates a barrier between the areas where your thighs rub.
You can shop Flissie bamboo boxer shorts here.
A waistband that doesn't dig in
High-waisted leggings plus a tight elastic underwear band is not always the most comfortable combination.
Look for a wider waistband that sits flat against the body rather than a narrow piece of elastic that creates pressure in one area.
This becomes particularly noticeable during seated exercises, cycling or anything involving repeated bending at the waist.
Briefs vs boxer shorts for the gym: coverage or freedom of movement?
There’s no single type of underwear that every person needs to wear at the gym.
It comes down to your workout and what you find comfortable.
Traditional briefs have less fabric, which some people prefer underneath tight gymwear. If you don’t struggle with thigh friction or underwear moving around, they might work perfectly well for you.
The disadvantage is that there’s very little coverage through the upper thigh.
That means if your thighs rub when you walk, run or exercise, there’s nothing between the skin to prevent that friction.
Longer boxer shorts approach the problem differently.
Instead of leaving the thigh exposed, the fabric extends further down the leg. When the fit is right, this creates a smooth layer between your thighs while still allowing you to move freely.
For gym sessions involving:
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Treadmill walking
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Cross trainer workouts
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Weight training
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Strength classes
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Spin
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Pilates
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General gym sessions
…a longer leg can be particularly comfortable.
Flissie’s 6-inch length sits around the mid-thigh, making it an easy option beneath most gym leggings and shorts.
The 9-inch version offers additional thigh coverage if chafing is your biggest concern.
If you’re unsure which size or length will suit you, have a look at the Flissie size guide before ordering.
The case for bamboo when you're sweating several times a week
When you start exercising regularly again, your underwear gets put through quite a lot.
Wear it. Sweat in it. Wash it. Repeat.
That’s where fabric choice becomes particularly important.
Flissie boxers are made from 95% Tanboocel bamboo viscose with 5% elastane, creating a soft, stretchy fabric designed to sit close to the body without feeling restrictive.
Bamboo viscose feels incredibly soft against the skin, which can be especially welcome when you’re doing repetitive movements.
It’s also breathable and helps move moisture rather than simply holding it against the body.
That doesn’t mean bamboo is automatically the perfect fabric for every type of exercise.
If you’re doing a very high-intensity session, marathon training or exercising for long periods in extreme heat, highly technical synthetic sports underwear may dry more quickly.
For normal gym sessions and everyday exercise, however, bamboo offers a useful balance between breathability, softness and comfort.
If running is your main form of exercise, our guide to the best anti-chafing underwear for running goes into running-specific options in much more detail.
For the gym, the priority is often slightly different.
You want something comfortable enough to wear regularly, easy enough to incorporate into your normal underwear drawer and reliable enough that you aren’t adjusting it throughout your session.
Don't underestimate thigh chafing at the gym
Chafing isn’t only something that happens on long runs.
Repeated movement can create friction during almost any form of exercise, particularly once sweat is involved.
Treadmill walking, stair machines, cross trainers and high-repetition leg workouts can all mean your thighs repeatedly moving against each other.
If this is an issue for you, longer underwear can help by putting a layer of fabric between the areas that usually rub.
The important bit is the length.
Very short boxer-style underwear might look similar, but if the leg finishes above the area where your thighs touch, it won’t offer much protection from friction.
That’s why Flissie boxers were designed with longer 6-inch and 9-inch inseams.
You can also read more about anti-chafing shorts and how longer-leg underwear works.
Building a no-fuss gym underwear rotation
If you’re exercising several times a week, having one designated “gym pair” quickly becomes annoying.
You either end up constantly washing it or discovering it’s sitting at the bottom of the laundry basket five minutes before you need to leave.
A small rotation makes things much easier.
If you normally work out three times a week, for example, having several pairs ready means you aren’t organising your laundry around your gym schedule.
And because good workout underwear doesn’t need to look particularly sporty, there’s no reason it can’t double up as everyday underwear too.
That’s particularly useful if you’re heading straight to the gym after work or squeezing a session into the middle of a busy day.
Flissie boxer shorts are designed for everyday comfort as well as active days, so you don’t necessarily need separate underwear drawers for “gym” and “normal life”.
The Flissie boxer multipacks also make it easier to build a rotation and choose colours and lengths that work with your wardrobe.
Then your pre-gym routine really can be as simple as getting changed and going.
What about underwear lines under gym leggings?
It’s one of the most common concerns when choosing underwear for the gym.
Tight leggings have an unfortunate ability to reveal almost every seam beneath them.
Longer boxer shorts can actually work well here because the edge of the underwear sits further down the thigh rather than cutting directly across the bottom.
Fit matters, though.
Anything too tight can create lines, while anything too loose can bunch.
Choose the correct size and make sure the leg sits smoothly against the skin before pulling your leggings on.
Flissie currently offers sizes from UK 8 to UK 30, and if you’re between sizes, we recommend sizing up.
Check your measurements against our full Flissie size guide.
Your gym underwear should be the thing you forget about
There’s already enough to think about when you’re getting back into an exercise routine.
Which workout you’re doing.
Whether the squat rack is free.
How many reps you have left.
Where you put your water bottle.
Your underwear really shouldn’t make that list.
The best gym underwear is often the pair you completely forget you’re wearing.
Soft fabric. A comfortable waistband. Enough coverage. No constant pulling, adjusting or rearranging.
Simple.
And if September is your month for getting back into a routine, upgrading the basics might make those first few weeks feel just that little bit easier.
Gym underwear FAQs
What is the best underwear to wear to the gym?
Look for underwear that is breathable, comfortable, stretchy and stays in place while you move. The right option depends on your workout and personal preference, but longer-leg underwear can be particularly useful if you experience thigh friction or find briefs ride up while exercising.
Are boxer shorts good for working out?
They can be. Boxer shorts designed to fit close to the body offer more thigh coverage than traditional briefs while still allowing plenty of movement. Avoid very loose boxer styles, which may bunch beneath gym leggings or shorts.
Is bamboo underwear good for exercise?
Bamboo viscose is soft, breathable and comfortable against the skin, making it a good option for regular gym sessions and everyday exercise. For extremely high-intensity or endurance exercise where very rapid drying is the priority, technical synthetic sports fabrics may be better suited.
What underwear should I wear under gym leggings?
Choose something that sits smoothly against the body and doesn’t dig into your waist or ride up as you move. Longer boxer shorts can work particularly well because the leg finishes further down the thigh instead of creating a traditional underwear line across the bottom.
How can I stop chafing at the gym?
Reducing skin-on-skin friction is one of the simplest ways to prevent thigh chafing. Longer underwear can create a soft barrier between your thighs, while breathable fabric can help keep the area more comfortable when you sweat.
Should I choose the 6-inch or 9-inch Flissie boxers for the gym?
For general gym workouts, the 6-inch length gives plenty of coverage while sitting around mid-thigh and works well beneath most gymwear.
If thigh chafing is your main concern or you simply prefer more coverage, you may prefer the 9-inch length.
Ready to make your gym kit more comfortable?
Getting back into a routine is hard enough without uncomfortable underwear getting in the way.
Discover soft, breathable bamboo boxers designed to stay comfortable while you move.
