Lined vs Unlined Running Shorts: Which Should You Wear?
By BOA | Running Shorts & Apparel | Made in the USA | Published: 2026-10-14
Category: Comparisons
Lined shorts mean no underwear and fewer moving parts; unlined shorts give you control. Here's how to choose based on distance, fit, and chafe risk.
Quick answer
Choose lined running shorts for most training runs because the built-in brief replaces underwear, removes a waistband that can shift, and cuts a common chafe source. Choose unlined shorts when you want to control your own base layer, need to change after a workout, or prefer a looser, non-restrictive feel. On race day, unlined racing shorts are common because they are lighter, but only if your base layer stays put.
What the liner actually does
A liner is a sewn-in brief or short that sits against your skin. It gives light support, keeps fabric from riding up, and means you wear the short without underwear. That last point matters: running shorts without underwear is a deliberate choice, not a mistake, because a second waistband and cotton fabric are two of the most common causes of chafing on long runs.
Lined shorts also reduce decisions. You grab one item, and the support is already there. The trade-off is that the liner is fixed. If it bunches, digs, or holds sweat, you feel it for the whole run and you cannot swap it out.
Where unlined shorts win
Unlined shorts give you a blank shell. You pair them with whatever base layer you already trust, from a seamless brief to a compression short. That is useful if you race in a specific setup, if you want to change out of sweaty shorts after a workout, or if you simply dislike the feel of a built-in brief.
The cost is one more item to manage. An unlined short only works as well as the layer under it, and a base layer that shifts or bunches will cause problems the liner was designed to prevent.
How to test a liner before race day
Do not debut a liner on race day. Wear it on a run at or near your goal distance, in the conditions you expect. Check three things: whether the liner stays in place when you pick up pace, whether the leg opening rubs, and whether the fabric dries or holds moisture.
If a liner passes those checks, it is doing its job. If it fails one, an unlined short with your own base layer is the more reliable choice, even if it adds a step to getting dressed.
Fit and sizing when you order online
Fit matters more with a liner because there is no adjusting it. Check the size range before you buy. The Men's Custom Ultra Mesh Racing Singlet, for example, is available from XXS to 4XL, which shows how wide sizing can run on performance tops and singlets from the same catalog. A short with a fixed liner should fit snugly at the waist without compressing, and the liner should sit flat, not roll.
If you are between sizes and plan to wear a base layer, size for the layer, not the number. If you plan to wear the liner alone, size for the liner.
Trade-offs at a glance
- Chafe risk: Lined shorts remove a second waistband and cotton underwear, which are frequent chafe points. Unlined shorts depend entirely on the base layer you choose. If you chafe easily, start with a lined short.
- Support and adjustment: A liner is fixed, so it either fits or it does not. An unlined short lets you swap base layers until the support feels right. If you are between sizes, unlined gives you more room to adjust.
- Race-day weight and simplicity: Unlined racing shorts are often chosen for a lighter feel, but they require a base layer that stays put at pace. Lined shorts are one item and no decisions. Test the setup at race pace before you commit.
Catalog facts that affect the choice
- Men's Custom Ultra Mesh Racing Singlet - SL04H-Inter MooreJ: Men's Custom Ultra Mesh Racing Singlet from BOA is a lightweight, breathable option with ultra mesh fabric that promotes airflow, made in the USA, in sizes XXS to 4XL. On hot race days, an upper layer that moves air helps, and the wide size range means you can match the singlet to the same fit logic you use for shorts.
- Women's Short Sleeve Raglan Tee Slim Fit - Charcoal: Women's Short Sleeve Raglan Tee Slim Fit - Charcoal is designed as an everyday tee that goes from track to trail to gym, and is available in Color and Size. A versatile top like this works with either lined or unlined shorts, so it does not force a decision on your lower half.
- Men's Full Custom Uniforms Cypher Custom Men's 3" Half Split Trainer. (x 1): Men's Full Custom Uniforms Cypher Custom Men's 3" Half Split Trainer is a 3-inch half split trainer with a custom colorway and a note that the BOA logo must be visible. A short 3-inch split is the kind of minimal racing cut that is often worn unlined, so it is a good test case for whether you prefer a separate base layer.
Who should choose which
Choose lined shorts if
- You want one item and no base-layer decisions on training runs
- You chafe from underwear waistbands or cotton fabric
- You run mostly easy to moderate distances and want predictable support
Choose unlined shorts if
- You already have a base layer you trust and want to keep using it
- You need to change out of your shorts right after a workout
- You prefer a looser feel and will test your base layer at race pace
