To find your size in women's performance kit, start from your usual women's size, then use the fitted-chest, relaxed-stomach principle and the product page fit notes to confirm the exact fit rather than defaulting up or down. THETA cuts precisely per size, so the right choice sits close through the chest and shoulders with room to brace at the stomach.
- THETA's tech tops are precision-cut per size and built to a fitted-chest, relaxed-stomach standard.
- The deciding cue is not your usual size but the fitted-chest, relaxed-stomach standard: snug up top, easy through the middle.
- A HYROX race is worn through 8km of running and 8 stations, so fit under movement matters more than fit standing still.
What actually decides your size?
Your usual size is a starting reference, not the answer, and the mistake most buyers make is treating it as the answer and then defaulting up or down from it out of habit. The thing that actually decides the size is how the piece is cut, and THETA cuts to a single, deliberate standard: fitted through the chest and shoulders, relaxed at the stomach, precision-cut per size rather than graded off a men's block. Read against that standard, your true size is usually correct, because the roominess you would size up to find is already built into the stomach. Where two sizes feel plausible, the per-size fit notes on each product page break the tie, telling you whether a specific piece runs closer or roomier, which matters because a race singlet and a training tee are cut to do different jobs. Sizing is that cut, checked against the notes, not a guess or a default.
What does "fitted chest, relaxed stomach" mean for choosing a size?
Most people size up for comfort. It is the wrong instinct here. THETA cuts tops to sit close through the chest and shoulders while leaving room at the stomach, so the right size feels snug up top and easy through the middle. Loose across the chest and shoulders means the top is too big, and it will flap on the run and ride up overhead. Restriction at the ribs or the brace at the stomach means it is too small. Read both cues together, and if a size fits the chest but pulls at the stomach, let the fit notes guide you rather than simply sizing up.
How should shorts and waistbands fit?
Shorts should sit secure at the waist without digging. The body should be squat-proof and stay opaque at depth. THETA's Women's Gym Shorts use a 3-tier waistband that stays anchored under load, so the right size holds without over-tightening. Test it. Squat and lunge deep: the fabric should stretch freely and recover to shape, and the waistband should stay put. If you have to cinch it hard to stop it sliding, size down. If it digs at the waist, size up, and check the fit notes for the specific short.
| Sign | Meaning | Action |
|---|---|---|
| Loose across chest and shoulders | Top too big | Size down or check fit notes |
| Restricts brace at stomach | Top too small | Size up |
| Waistband digs | Short too small | Size up |
| Waistband slides at true tension | Short too big | Size down |
How do you confirm the size is right?
- Start from your usual women's size and read the product page fit notes for that piece.
- Check the top is fitted across the chest and shoulders with room at the stomach.
- Raise your arms overhead and confirm the hem stays near the waist.
- Squat and lunge deep to confirm the shorts stretch, recover and stay opaque.
- Test the kit soaked in a full session, since sweat changes how fit and coverage behave.
"The most common sizing mistake is defaulting up for comfort. Our tops are cut fitted at the chest and relaxed at the stomach on purpose, so your true size usually is the comfortable one. Trust the fit notes and test it moving," says the THETA coaching team.
What if you are between two sizes?
Being between sizes is the most common sizing question, and the answer depends on the piece rather than a blanket rule, which is exactly why the per-size fit notes exist. For a race top where the job is to stay anchored and shed heat, the smaller of two sizes usually wins, because a fraction too much fabric flaps on the run and climbs overhead, undoing the whole point of a fitted chest. For a training piece you will wear for long, varied sessions, or if the smaller size restricts your brace at the ribs, the larger size can be the better call. Shorts follow the waistband: if the smaller size holds without you having to over-tighten it, take it, and if it digs at the waist to stay up, size up. The mistake to avoid is applying one instinct to everything, because a singlet and a tee are cut for different jobs and can land you on different sizes even at the same body measurement.
Why does testing under movement matter?
Kit that fits standing still can still fail once you move. Running, reaching and lunging reveal the ride-up, sliding and gapping a mirror hides. A race top is worn through 8km and 8 stations, so the real test is whether it stays anchored overhead and covered at depth, not how it looks standing there. That is why you rehearse your size in a full soaked session. If it stays put and comfortable through the movements that matter, the size is right. If not, the fit notes guide the adjustment.
One practical note on doing this test cheaply: you do not need a race to run it. A single hard interval session that soaks the kit and includes overhead reaches and deep lunges will surface almost everything a race would, because the failures are triggered by movement and sweat, not by the event itself. Wear the new size for that session with the tags kept and the receipt safe, and you will know inside forty minutes whether it is the right size, long before it matters on a start line.
Common questions
How do I find my size in women's performance kit?
Start from your usual women's size, then confirm with the fitted-chest, relaxed-stomach cue and the product page fit notes. THETA cuts precisely per size, so your true size is usually correct rather than sizing up for comfort.
Should I size up in performance tops?
Usually not, because sizing up adds loose fabric that flaps on the run and rides up overhead. THETA's relaxed-stomach cut already provides bracing room, so stick to your true size unless the fit notes say otherwise.
How should a women's performance top fit?
It should sit fitted across the chest and shoulders with room at the stomach, staying anchored when you reach overhead. Loose across the chest means too big; restriction at the stomach means too small.
How do I know if shorts are the right size?
The waistband should stay secure without digging, and the squat-proof body should stretch, recover and stay opaque at depth. If you must over-tighten to stop sliding, size down; if the waist digs, size up.
Do THETA's women's pieces run true to size?
They are precision-cut per size to a fitted-chest, relaxed-stomach standard, so starting from your true size is the right reference. Check each product page's fit notes, since a race singlet and a training tee can fit differently.
Sources
- THETA product development notes and female-athlete testing, 2024-2026
- HYROX race format and station demands (hyrox.com)
- Established principles of technical-garment fit and sizing