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How To Spot Quality Activewear: Flatlocked Seams

As a public service, I’m going to offer my expertise in identifying quality activewear in a series. Behold! Part 1: flat locked seams!

What are flat locked Seams? Flat lock is an interlocking stitch that reduces bulk and 3 dimensional edges to cut down on chafing and seams rubbing against the body. Most activewear manufacturers recognize it as important use it to some extent; Lululemon and Lucy use it extensively, but it even has become more incorporated into designs at Target and Walmart.

The seams also, well, lay flat so the garment has a more polished, pressed appearance. Where there is detail work or body mapping flat locked seams are a must to cut down on puckering where the two fabrics meet. Sometimes the flat locked stitch is used to add detail or interest even though there is no actual seam.


In the above picture,the blue color blocked top shows the flat locked stitch. The orange top, from JCPenny’s Xersion line, has a regular interlock stitch which is commonly used on stretch fabrics. Frequently, in lower priced activewear you will find regular interlock stitches used for the side seams even if other parts of the garment are flat locked. Now sure why. It must save money, somehow.

Regular interlock seams aren’t necessarily a deal breaker, depending on where they are. If you are buying the clothing for a specific activity and are anticipating lots of friction when the regular seams are that item of clothing is probably not the best.

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