Running Shorts vs Gym Shorts: What's the Difference and Does It Matter?

Running shorts and gym shorts are not the same thing. Running shorts are lighter, shorter, and built with an internal liner that replaces underwear and manages sweat over long distances. Gym shorts are typically heavier, looser, and made for bending, squatting, and lifting — with no liner and often deeper pockets. You can blur the lines for a casual workout, but if you're running more than a couple miles or lifting heavy, the right pair makes a real difference.

If you've ever grabbed whatever shorts were clean and wondered why your run felt soggy or your squats felt restricted, the explanation is probably in the design. Let's break down what separates running shorts from gym shorts — and when it actually matters.

What Are Running Shorts?

Running shorts are purpose-built for forward motion at speed. They're cut above the knee (typically 5–7 inch inseams for men), made from ultralight polyester or nylon-spandex blends, and almost always include a built-in liner — that fitted inner brief that replaces underwear and wicks sweat away from your skin.

A pair like the Rx110 Men's Lined Running Shorts hits all of these marks: a lightweight, breathable shell, a lined support interior, and a secure zip pocket for your phone or key. Velurem designed them specifically for running, gym sessions, and high-output training where sweat management and freedom of movement matter.

The defining trait of a running short is that it's engineered to minimize anything that could slow you down or cause friction over thousands of strides. Every gram of fabric, every seam placement, and every inch of inseam length is chosen with that goal in mind.

What Are Gym Shorts?

Gym shorts are built for training that involves a lot of bending, squatting, lifting, and static movement. They tend to be:

• Heavier fabric. Often a thicker polyester blend, sometimes with cotton content. More durable, but traps more heat.
• Longer and looser. Inseams of 7–10 inches are common, with a roomier fit through the leg to allow deep squats and lunges without riding up.
• No liner. Most gym shorts don't have a built-in brief. You wear your own underwear underneath.
• Bigger pockets. Side pockets or cargo-style pockets for your phone, wallet, or gym card. Sometimes a drawstring waistband instead of elastic only.

Gym shorts prioritize coverage and utility over weight and breathability. They're fine for a treadmill jog, but they're not built to handle the specific demands of outdoor running.

The 5 Key Differences Explained

1. The Liner

This is the single biggest difference. Running shorts have one; gym shorts usually don't.

The liner in a running short is a fitted inner layer that sits against your skin, wicks sweat, provides support, and prevents chafing. It means you don't wear underwear — the liner does that job. We covered this in depth in our guide to why running shorts have liners, but the short version is: if your shorts have a liner, they're running shorts.

Gym shorts skip the liner because lifters typically prefer their own underwear or compression shorts underneath. The extra room also makes deeper movements like squats more comfortable.

2. Fabric Weight and Breathability

Running shorts use lightweight, high-wicking fabrics — usually 4-way stretch polyester or nylon-spandex blends weighing around 3–5 ounces for the whole pair. The fabric is thin enough that you can see light through it when held up. That thinness is the point: it dumps heat fast and dries quickly.

Gym shorts tend to run 6–10 ounces. The thicker fabric holds up better to abrasive gym surfaces (benches, kettlebell racks, turf) but holds more heat and takes longer to dry after a sweaty session.

3. Length and Cut

Running shorts are shorter — 5, 6, or 7 inch inseams are standard for men's running shorts. The shorter cut maximizes stride length and reduces fabric that could bunch or chafe on the inner thigh.

Gym shorts run longer: 7, 9, or even 10+ inch inseams. The extra length gives more coverage for floor work, stretching, and exercises where your shorts might ride up or shift. The looser cut through the thigh accommodates larger leg muscles during squats and deadlifts.

4. Pockets

Running shorts often have minimal pocket space — sometimes just a small zip pocket sized for a key or card. The reason is simple: bouncing phones and loose items are annoying and distracting over miles of running. The Rx110's zip pocket is a good example: just big enough for a phone or key, secured so nothing moves.

Gym shorts frequently have full side pockets, sometimes with phone-sized openings. Since you're mostly stationary during lifts, a phone in your pocket isn't going anywhere, so the extra storage makes sense.

5. Waistband Design

Running shorts usually have a flat, wide elastic waistband with an internal drawstring. The wide band distributes pressure evenly and doesn't dig in during repetitive forward motion.

Gym shorts often use a narrower elastic band with an external drawstring. Some have a heavier drawstring for a more secure fit during exercises that involve bending at the waist.

Can You Run in Gym Shorts?

Yes, but with trade-offs. If you're doing a short, easy run — a mile or two on a treadmill, a warmup jog before lifting — gym shorts are fine. Most people won't notice the difference at that distance.

Beyond that, the problems start:

• No liner means more chafing risk. Underwear shifts and bunches over thousands of strides, and cotton underwear holds sweat against your skin.
• Heavier fabric means more heat. On a hot day or a long run, gym shorts trap warmth that running shorts would dump.
• Longer length means more friction. Extra fabric on the inner thigh is the most common cause of chafing in runners.
• Loose pockets mean bouncing gear. A phone in a side pocket at running pace is a constant distraction.

If running is your main activity, gym shorts will work in a pinch but you'll feel the difference quickly.

Can You Lift in Running Shorts?

Yes, and this is where the lines blur more. Running shorts work well for many gym exercises:

• Upper body lifts (bench press, overhead press, rows): no issue at all. Shorts length and fabric don't affect these.
• Core work (planks, sit-ups, ab rollouts): running shorts are actually better here — lighter and cooler.
• Leg extensions and curls (machine-based): usually fine, though the liner may feel snug during deep knee flexion.

The main conflict is deep barbell squats and deadlifts. Running shorts are cut shorter and tighter, which can ride up during a deep squat. The liner may also feel restrictive if you're used to the roomier fit of gym shorts. Some runners solve this by sizing up, but that defeats the running fit.

If your workout mixes running and lifting — like a CrossFit-style session or a run-then-lift routine — a 2-in-1 lined short like the Rx110 is the best compromise. The liner handles the running; the shell is cut loose enough for most lifting.

Which Should You Buy?

It comes down to what you do most:

• Run 3+ times per week? Get dedicated running shorts with a liner. The comfort difference on anything over 2 miles is significant, and you'll chafe less, stay cooler, and carry less weight. Browse running shorts and other wellness gear at Velurem for options.
• Mostly lift, with occasional cardio? Gym shorts are fine. The extra room and durability suit heavy training, and a short treadmill jog won't expose the gap.
• Mix both equally? A 2-in-1 lined running short is your best bet. The liner gives you running performance, and the looser shell handles most gym work. The Rx110 lined running shorts are designed exactly for this hybrid use.

Does It Actually Matter for Casual Workouts?

If you're doing 20–30 minutes of mixed exercise a few times a week — a short jog, some bodyweight squats, a few push-ups — the difference between running shorts and gym shorts is marginal. Either will work.

The gap shows up when you push distance, intensity, or frequency. A 6-mile run in gym shorts on a humid day is a different experience than the same run in lined running shorts. A heavy squat session in short, tight running shorts feels different than in roomier gym shorts. The design choices that make each type great for its primary activity are the same choices that make it worse for the other.

Frequently Asked Questions

Can I use running shorts for the gym?

Yes, for most exercises. Running shorts work well for upper body lifts, core work, and machine-based leg exercises. They may feel too short or tight for deep barbell squats, but for a mixed run-and-lift session they're a solid all-around choice.

Do gym shorts have liners?

Most don't. Gym shorts are designed to be worn with your own underwear or compression shorts underneath. If a pair of shorts has a built-in fitted liner, it's almost always a running short.

Why are running shorts so short?

Shorter inseams (5–7 inches for men) maximize stride length and reduce fabric that can bunch, ride up, or chafe on the inner thigh. The lighter, shorter cut also dumps heat faster, which matters on long runs and hot days.

Are 2-in-1 shorts the same as running shorts?

2-in-1 shorts are a type of running short. The "2-in-1" refers to the two-layer construction: an inner liner (layer one) and an outer shell (layer two). They're the most versatile option for people who both run and lift.

Can I swim in running shorts?

You can, but they're not designed for it. Running shorts lack the water-shedding fabric and inner construction of swim trunks, and the liner may hold water. For a casual dip after a run, fine. For regular swimming, get proper swim shorts.

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Looking for the right pair? Check out the full collection of health and wellness gear at Velurem, or browse more guides on the Velurem blog.