Do You Wear Underwear Under Lined Running Shorts?
Are You Actually Supposed to Wear Underwear Under Running Shorts With a Liner?
There is a tiny piece of activewear engineering that causes a surprisingly large amount of confusion.
The built in liner.
You buy running shorts.
You look inside.
There is already another layer there.
And immediately comes the question.
Do I still wear underwear?
Usually, a proper running short liner is designed to perform much of the job that underwear would otherwise do.
That is why the Women's High Waist Sports Shorts with Liner is more interesting than its simple appearance suggests.
ILLUSION CO currently lists the shorts at $34.95 AUD, reduced from $54.95 AUD, in Blue, Dark Red, Black and Grey, with sizes S through XL. The live listing also confirms a high waist, quick dry fabric containing 90 percent polyester, a built in liner and a split hem intended to provide more freedom during movement.
Those details make this a good excuse to answer the question properly.
What Is a Built In Liner Actually For?
A liner is the inner layer sewn into many running and training shorts.
Its purpose is not simply to make the garment thicker.
It can provide coverage, help keep the outer short from exposing too much during movement and reduce the need for a completely separate undergarment.
Runner's World notes that liners in running shorts are generally intended to replace underwear. Their current women's running shorts guide explains that the liner is designed to help avoid the bunching and wedging that can happen when another undergarment moves independently beneath the short.
So yes, in many cases the strange extra layer inside your running shorts is there precisely because the manufacturer expects it to be the first layer against the body.
Does That Mean You Must Skip Underwear?
No.
Activewear is not a legally binding contract.
Some people prefer wearing underwear beneath lined shorts because it feels more familiar.
Others find that an additional layer creates more heat, moisture and fabric movement.
Runner's World notes that adding underwear beneath an existing liner can contribute to sweat build up and friction for some runners.
The best answer is therefore less dramatic than the internet sometimes makes it.
If the liner is comfortable by itself, you may not need another layer.
If you personally prefer underwear, you can wear it.
The real test is whether the combination remains comfortable once you start moving.
Why Two Comfortable Layers Can Become Uncomfortable Together
Imagine two pieces of fabric sitting perfectly while you stand still.
Then start running.
One stretches.
One slides.
One absorbs moisture at a different rate.
One shifts slightly to the left.
Now those surfaces are rubbing against each other and against your skin thousands of times over the course of a workout.
That is why activewear should never be judged only while standing in front of a mirror.
Running creates repetition.
A tiny irritation that feels irrelevant after thirty seconds can feel very different after thirty minutes.
Chafing Is Mostly a Friction Problem
Chafing occurs when repeated rubbing irritates the skin.
Moisture can make the situation worse.
The thighs are a common problem area for runners because skin, seams or fabric may repeatedly rub during movement.
This is one reason running short design matters more than people sometimes assume.
Runner's World's 2026 testing places comfort, chafing and storage among the major things runners should evaluate when choosing shorts. Its testers also found that liner design can materially affect whether a pair stays comfortable during running.
A liner is therefore not automatically anti chafing.
It still has to fit properly.
A Bad Liner Can Be Worse Than No Liner
This is worth saying because activewear marketing often treats every additional feature as automatically beneficial.
A liner that is too loose can bunch.
One that is too tight can dig into the body.
Poorly positioned seams can create friction.
A liner that shifts independently from the outer short can become distracting.
Runner's World specifically recommends evaluating liner fit because some liners can still create chafing if the fit or seams are wrong.
So the presence of a liner tells you what the garment is trying to do.
Your body tells you whether it succeeds.
This Is Where the Women's High Waist Sports Shorts with Liner Gets Its Name
ILLUSION CO specifically states that the built in liner is intended to provide extra coverage and help prevent exposure during movement.
That is especially relevant with looser outer shorts.
A split hem gives the outer layer more freedom to open as the legs move.
That is useful for range of motion.
It also means the inner layer becomes more important.
The outer short can move more freely while the liner provides another level of coverage underneath.
Those two features are therefore connected.
They are not simply random details added to the description.
The Split Hem Is About Movement
Look at traditional running shorts and you will often notice that the side of the leg is not completely closed.
There may be a curved opening or split.
Why?
Because your legs do not remain vertical while exercising.
Running requires the thigh to travel forward and backward.
Lunges require a large range of motion.
High knees increase it further.
A rigid hem can restrict that motion or pull the garment upward.
The current ILLUSION CO listing states that these shorts use a split hem specifically to allow greater freedom of movement.
Simple detail.
Useful consequence.
Coverage and Freedom Can Exist Together
This is really the clever part of lined shorts.
The outer layer can be relatively loose.
The hem can move.
The leg opening can provide freedom.
Meanwhile the inner layer helps maintain coverage.
Without the liner, shoppers might respond by choosing a tighter outer garment simply to feel secure.
With two layers performing different jobs, the outer short does not have to do everything.
That is a recurring theme in good clothing design.
One part provides movement.
Another provides stability.
Why High Waistbands Keep Showing Up in Activewear
The Women's High Waist Sports Shorts with Liner also uses a high waist construction. ILLUSION CO describes this as providing a flattering fit and additional support during wear.
For exercise, waistband position matters because the torso bends repeatedly.
A waistband that feels perfectly comfortable while standing may roll, slide or dig when you squat.
Runner's World's 2026 women's running short guide notes that wider waistbands can be comfortable because they distribute contact across a broader area rather than concentrating pressure into a narrow strip.
That does not mean every high waist automatically fits well.
Again, fit decides.
Do the Squat Test
Before deciding that any workout shorts fit properly, move in them.
Squat.
Lunge.
Sit.
Walk.
Lift one knee.
Then the other.
Jog lightly if you have enough room.
Pay attention to whether the waistband moves excessively, whether the liner shifts and whether the outer short rides upward.
The garment is designed for movement.
Evaluate it during movement.
A mirror selfie is useful for colour.
It is less useful for biomechanics.
Then Do the Phone Test
This pair is not currently verified by the live listing as having a specific pocket configuration, so I would not invent one.
But the broader lesson still matters.
If you choose running shorts with pockets, test them with whatever you intend to carry.
Runner's World notes that pocket design has become a major factor in modern running shorts because runners increasingly carry phones, keys, cards and nutrition.
A pocket is only useful if the item inside does not bounce so aggressively that you begin questioning why you brought it.
Quick Dry Does Not Mean Sweat Proof
ILLUSION CO describes the Women's High Waist Sports Shorts with Liner as using quick dry fabric with 90 percent polyester.
Quick dry should not be interpreted as does not get wet.
You can still sweat.
The fabric can still become damp.
The claim is about the material drying relatively quickly.
That can matter during running, gym sessions, travel or warm weather because damp fabric sitting against the body can become uncomfortable.
It also makes the garment easier to wash and reuse when travelling.
Polyester Is Popular in Activewear for a Reason
Polyester absorbs relatively little water compared with highly absorbent natural fibres.
That helps explain why it appears so frequently in workout clothing.
But fibre content alone cannot tell you everything about performance.
Fabric weight matters.
Weave matters.
Construction matters.
Fit matters.
Finishing treatments may matter.
The live ILLUSION CO page verifies 90 percent polyester but does not clearly identify the remaining fibre percentage, so it would be inaccurate to guess.
Knowing where product information stops is part of shopping intelligently.
Your Liner Needs Washing Too
This should be obvious.
Yet gym bags suggest otherwise.
A liner sits close to the body and can collect sweat.
After training, wash the shorts according to the care label and let them dry fully before storage.
Do not leave damp activewear crumpled inside a closed bag for three days and then become shocked that the bag has developed its own weather system.
Runner's World recommends washing sweaty shorts and notes that appropriate liner fabrics can help manage moisture, but the garment still needs normal laundering.
Fabric Softener Is Worth Checking Before You Use It
Some performance clothing manufacturers advise against fabric softener because residue can interfere with moisture handling in certain technical textiles.
Runner's World similarly recommends skipping fabric softener for sweat managing running garments and suggests air drying as one way to help preserve them.
The care label on your exact shorts should remain the final authority.
Generic activewear advice should never overrule the manufacturer's specific instructions.
What About Sweat Marks?
The current colour options are Blue, Dark Red, Black and Grey.
People often assume black will hide sweat and grey will show everything.
Sometimes that happens.
But colour alone cannot guarantee how visible moisture will be.
Fabric thickness, finish and how saturated the material becomes all influence appearance.
If visible sweat matters to you, darker options may feel psychologically safer, but no responsible product description should promise invisible sweat without evidence.
Sweating during exercise is normal anyway.
Your shorts are attending a workout.
They know what they signed up for.
So Who Actually Benefits From a Built In Liner?
A liner makes particular sense for people who prefer loose outer shorts but still want additional coverage during running, gym sessions, yoga or other movement.
It can also simplify dressing by eliminating a separate layer when the liner is designed to replace underwear.
That does not mean everyone will love it.
Some athletes deliberately choose unlined shorts because they prefer their own underwear or base layer.
Others will actively search for lined designs.
Neither group is wrong.
This is personal preference meeting garment construction.
The Important Question Is Not Lined or Unlined
It is whether the system works together.
Waistband.
Outer short.
Liner.
Hem.
Fabric.
Size.
These features interact.
A brilliant liner cannot save a waistband that constantly slides.
A perfect waistband cannot fix a liner that bunches.
Quick dry fabric does not help much if the fit creates constant friction.
Good activewear is rarely about one miracle feature.
It is usually several ordinary details working correctly at the same time.
Frequently Asked Questions
Do you wear underwear under running shorts with a liner?
Usually you do not need to. Running short liners are commonly designed to replace underwear. Runner's World notes that adding another layer can sometimes contribute to bunching, heat and friction. Personal comfort still matters, so there is no universal rule.
What is the Women's High Waist Sports Shorts with Liner?
It is a women's activewear short with a high waist, built in liner, quick dry fabric and split hem. ILLUSION CO currently positions it for running, yoga, gym use and casual wear.
How much is the Women's High Waist Sports Shorts with Liner?
ILLUSION CO currently lists it at $34.95 AUD, reduced from $54.95 AUD.
What sizes are available?
The live listing currently shows S, M, L and XL.
What colours are available?
Current colour options are Blue, Dark Red, Black and Grey.
What is the liner designed to do?
ILLUSION CO states that the built in liner provides extra coverage and helps reduce unwanted exposure during movement. More generally, running short liners are often designed to perform the role of underwear.
Why do running shorts have split hems?
A split hem gives the leg opening more freedom as the thigh moves. ILLUSION CO specifically identifies greater freedom of movement as the purpose of the split hem on this model.
Can liners prevent chafing?
A well fitting liner may help by reducing loose fabric and eliminating an additional underwear layer, but liners can also cause irritation if they bunch, fit poorly or have uncomfortable seams.
Are these shorts quick drying?
ILLUSION CO describes the fabric as quick dry and verifies a composition containing 90 percent polyester.
Are the shorts currently in stock?
Yes. The live ILLUSION CO page currently shows the product as in stock.
Where can I compare more women's activewear shorts?
Browse the ILLUSION CO Women's Activewear Shorts collection for more workout short styles.
SHOP THE WOMEN'S HIGH WAIST SPORTS SHORTS WITH LINER
Maybe The Best Running Shorts Are Two Garments Pretending To Be One
From the outside, running shorts can look ridiculously simple.
Waistband.
Fabric.
Two leg openings.
Finished.
But the liner changes the design completely.
The outer layer can stay loose enough to move.
The split hem can open as the leg travels forward.
The inner layer can provide additional coverage.
And if the liner is comfortable enough to replace underwear, you may also remove an entire layer from the outfit.
That is the point of the Women's High Waist Sports Shorts with Liner.
The interesting feature is not simply that another piece of fabric has been sewn inside.
It is that the inner and outer layers are supposed to perform different jobs.
ILLUSION CO currently combines that built in liner with a high waist, quick dry fabric containing 90 percent polyester and a split hem, with Blue, Dark Red, Black and Grey options from S through XL.
The result is a useful reminder that good activewear does not always need some futuristic material with a twelve word trademark.
Sometimes the smartest feature is the layer you barely notice.
And if it is doing its job properly, barely noticing it is probably the entire point.