Patent-pending wearable prototypes

Apparel Prototyping: Kool Pressions Therapeutic Compression Leggings

GARMENT DESIGN
COMPRESSION ENGINEERING
PATTERN & PRINT DESIGN
MATERIAL SELECTION
PROOF-OF-CONCEPT PROTOTYPING
HIGH-FIDELITY PROTOTYPING

Written by Ralph Hill, Mechanical & electrical systems, 3D manufacturing

Prototyping Engineer

Published August 30, 2026

Apparel prototyping is the process of turning a garment concept into sewn, wearable samples that prove fit, function and appearance before anyone commits to a production run. For a performance garment it also has to prove a physical requirement — in this case therapeutic compression.

Kool Pressions, founded by Rhonda Young, is a patent-pending therapeutic compression legging cut as a stirrup so the toes and heels stay exposed, finished in bold custom prints. LA NPDT designed the garment, engineered how the compression is achieved, built a plain-fabric proof of concept, then produced custom-printed high-fidelity prototypes in several colourways for validation.

Project at a glance

Client: Rhonda Young, founder of Kool Pressions
Product: Patent-pending therapeutic compression stirrup legging with exposed toes and heels
Scope: Garment design, compression engineering, custom print development, proof-of-concept and high-fidelity prototypes
Colourways prototyped: Plain black plus custom multi-colour and grey geometric prints
Why it is unusual: Soft goods, not LA NPDT's usual mechanical and electromechanical work — taken on because the core problem was a functional one
Outcome: Wearable, photographable prototypes Rhonda could use to validate the concept before committing to production

A patent-pending stirrup legging taken from sketch to custom-printed, wearable prototypes.

The client

Rhonda Young approached LA NPDT with a clear idea and no way to hold it in her hands. Kool Pressions was to be a therapeutic compression legging that also flattered the lower body — cut as a stirrup so the toes and heels stay exposed, and finished in bold, unapologetically extravagant prints rather than the clinical black most compression wear defaults to. Our job was prototyping in a material we do not usually touch: fabric.

We designed the garment, engineered how the compression would actually be achieved, produced a proof-of-concept prototype, then printed custom patterns and built high-fidelity prototypes Rhonda could wear, photograph and put in front of prospective buyers to validate the concept.

The challenge

Therapeutic compression garments work by applying graduated pressure to the limb — higher at the ankle, tapering upward — a mechanism used clinically for circulation and swelling management (NCBI StatPearls: compression therapy). They also, almost universally, look medical. Rhonda's premise was that the two are not linked: the same engineered pressure can sit inside a garment with a slimming cut and a print worth showing off, and it will get worn far more often as a result. The stirrup detail was functional as much as aesthetic — leaving the toes and heels exposed keeps the garment wearable with sandals and open shoes, and avoids the hot, bunched foot that stops people wearing full-foot compression through a day (MedlinePlus on wearing compression stockings).

Garment design. Silhouette, panel layout, seam placement and the stirrup cuff geometry that holds the legging down without cutting into the arch.
Compression engineering. Fabric selection, stretch and recovery targets by zone, and the pattern reductions that turn a stated pressure into a cut piece of cloth.
Proof-of-concept prototype. A first sewn garment in plain fabric, made to test fit and pressure before any money went into printing.
Custom print development. Original repeating patterns laid out and printed on the fabric so the artwork lines up across panels and seams.
High-fidelity prototypes. Finished, wearable samples in several colourways for fit testing, photography and buyer conversations.

Plain black Kool Pressions compression legging proof-of-concept prototype laid flat on a workbench — The first sewn prototype in undyed stock.

Stack of early Kool Pressions fabric prototypes in black, maroon and grey heather — The first sewn prototype in undyed stock.

Our solution

Engineering the Compression

Compression in a knit garment is not a setting — it is the product of fabric modulus, how far that fabric is stretched when worn, and how the pattern is graded. We picked knits with the stretch and, more importantly, the recovery to hold pressure through a day rather than relaxing after an hour, then worked backwards from the pressure Rhonda wanted at the calf and thigh to the amount each pattern piece is reduced relative to the body measurement.

Seams were placed to avoid the pressure ridges that make compression wear uncomfortable, and the stirrup cuff was shaped so the tension that keeps the legging down is carried across the arch rather than concentrated at the heel. The same approach we use for a mechanical assembly applies here: identify the load, choose the material for it, and let the geometry distribute it.

Custom Prints and High-Fidelity Prototypes

With fit and pressure settled, the prints could be developed against a pattern that was no longer moving. Each artwork was laid out to the cut pieces so the repeat reads correctly on the leg and does not break awkwardly at the seams — the difference between a printed legging and a printed garment. We then produced high-fidelity prototypes in several colourways: a clothing prototype sewn and finished to the standard a buyer would expect off a shelf, not a fitting mock-up.

Design visualisation of a model wearing the multi-colour patterned Kool Pressions stirrup compression legging — The multi-colour print colourway.

Design visualisation of a model wearing the grey and black patterned Kool Pressions stirrup legging — The multi-colour print colourway.

Why an Engineering Firm Took On a Soft-Goods Project

This is not our usual work, and we will say so plainly: LA NPDT's core is mechanical and electromechanical devices — enclosures, mechanisms, circuitry and the low-volume manufacturing behind them. Kool Pressions was a deliberate stretch into a capability we hold but rarely advertise, run by the same engineering team in Ruston, Louisiana that develops our hardware projects. Rhonda's concept was patent pending during the work, so the prototypes had to match the filed design (USPTO patent process overview).

It worked because the problem was an engineering problem wearing fabric. Specifying a pressure, choosing a material by its stress–strain behaviour, prototyping to settle an argument, then holding a design still long enough to invest in tooling — in this case print files and printed fabric rather than moulds — is the same development process we run on hardware. Inventors with soft-goods concepts are usually choosing between a fashion studio that cannot engineer and an engineering firm that will not sew. We can do both, when the concept has a functional requirement at its centre.

Close-up of the Kool Pressions stirrup cuff showing the exposed heel and toe opening on the printed compression legging — The stirrup cuff: the detail that keeps the legging under tension while leaving toes and heels free.

The result

Rhonda left with wearable, photographable, patent-pending prototypes in multiple colourways — enough to test the concept with real wearers, shoot marketing imagery and hold a serious conversation with a manufacturer, without committing to a production run first. That is the whole point of prototyping: buy certainty before you buy inventory. If you have a garment or soft-goods concept with a functional requirement at its centre, talk to our team in Ruston, Louisiana — and see how the same process runs on hardware across our product development portfolio.

Capabilities used on this project

Rapid prototyping services
3D printing, CNC machining, urethane casting and functional prototype builds with published materials, tolerances and lead times.
Low-volume manufacturing
Bridge tooling, short-run production and supplier management for first commercial batches.

How a performance garment gets prototyped

The order matters: settle pressure and fit in cheap fabric, then spend money on print and finish.

Define the functional requirement, not just the look
For compression wear the requirement is a pressure profile — how much at the ankle, calf and thigh, and how it should taper. Everything downstream (fabric, pattern, seam plan) is derived from that number rather than from a sketch.
Select fabric for recovery, not only stretch
Any knit stretches. The property that decides whether a compression garment still works at hour eight is recovery — how completely the fabric returns after being held under strain. Candidate knits are compared on stretch and recovery together before the pattern is drafted.
Draft the pattern as a pressure calculation
Compression comes from cutting each panel smaller than the body it wraps. The reduction per zone is what converts the target pressure into cloth, so the pattern is graded against real measurements rather than a standard size block.
Sew a plain-fabric proof of concept
The first garment exists to be argued with. Made in undyed stock, it settles fit, cuff geometry, seam comfort and whether the pressure feels right — all before a single print file is produced.
Print, then build high-fidelity samples
With the pattern frozen, artwork is laid out to the cut pieces so the repeat reads correctly across panels and seams. Finished samples in each colourway then support wear testing, photography and buyer conversations.

Three ways an apparel concept gets prototyped

Route	What it does	Where it falls short
Sample from an overseas factory	Produces a sewn garment against a tech pack you supply	Assumes the design and the pressure engineering are already correct; iteration costs weeks per round
Fashion design studio	Delivers silhouette, styling and print artwork	Rarely engineers a functional requirement such as graduated compression
Engineering-led apparel prototyping	Derives fabric, pattern and seam plan from the stated function, then proves it in sewn samples	Best suited to garments with a performance claim; overkill for pure fashion pieces

Rapid prototyping services Prototype design Our product development process

Questions about this project

Straight answers from the engineers who ran the build. Have a different question? Ask us directly.

Talk to an engineer

What is apparel prototyping?

It is the process of turning a garment concept into sewn, wearable samples that prove fit, function and appearance before production. For performance garments it also validates the functional claim — compression, moisture handling, protection — in physical form rather than on paper.

How is compression actually engineered into a legging?

By combining a knit chosen for its stretch and recovery with a pattern that is deliberately smaller than the body measurement in each zone. The size of that reduction, zone by zone, is what produces the graduated pressure; seam placement then keeps that pressure from concentrating into ridges.

Why did the plain prototype come before the printed ones?

Because fit and pressure arguments are cheap to settle in undyed fabric and expensive to settle after print files, screens and finished samples exist. Freezing the pattern first meant the printed prototypes were presentation-quality rather than another test round.

Does LA NPDT normally do soft goods?

No. Our core work is mechanical and electromechanical products — enclosures, mechanisms, electronics and low-volume manufacturing. We took Kool Pressions on because the problem underneath the fabric was an engineering problem: a specified pressure, a material chosen for its stress–strain behaviour, and iteration to prove it.

What does an inventor get at the end of an apparel prototyping project?

Wearable samples in the intended materials and prints, the patterns behind them, and the evidence needed to talk to manufacturers, test with real users and shoot marketing imagery — without having paid for inventory first.

Industries this project belongs to

See how we approach development in each of these categories, and the other products we have taken from sketch to production there.

Sports & FitnessProduct development services

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Project at a glance

Engineering the Compression

Custom Prints and High-Fidelity Prototypes

Why an Engineering Firm Took On a Soft-Goods Project

Capabilities used on this project

Rapid prototyping services

Low-volume manufacturing

How a performance garment gets prototyped

Define the functional requirement, not just the look

Select fabric for recovery, not only stretch

Draft the pattern as a pressure calculation

Sew a plain-fabric proof of concept

Print, then build high-fidelity samples

Questions about this project

Industries this project belongs to

Silicone Prototyping: Clean Fingers Shellfish Eating Glove

QikPedi Step – Home Spa Product Design, Manufacturing, Marketing

Kool Jack Cooling Dog Vest: Product Development

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