There's a common belief that sewing lycra requires elastic thread, foam thread, or transparent thread. However, after more than 20 years making rhythmic gymnastics leotards, my recommendation remains the same: use a good quality polyester thread.
Why?
Because it's strong, durable, and holds up perfectly to the intensive use that leotards endure during training and competition.
Moreover, when seams break or burst, in most cases the problem is not the thread — it's an incorrect machine configuration.
The Secret Is in the Stitch and the Tension
If there's one thing that truly matters when sewing lycra, it's making sure the seam has stretch capacity.
To achieve this, I recommend using a tall, short zigzag stitch, creating a shape similar to a small accordion.
This structure allows the seam to follow the elasticity of the fabric as the gymnast moves, preventing breaks and unnecessary tension.
Many people try to solve this problem by using elastic or transparent threads, but the reality is that a well-configured seam with polyester thread delivers excellent results.
What truly matters is correctly adjusting the machine tension and running tests beforehand until you achieve a flexible stitch that can stretch with the lycra without breaking.
The Importance of Choosing Quality Lycra
The quality of the fabric is just as important as the sewing itself.
A good lycra must give correctly in both directions and, above all, have excellent recovery capacity.
That is, it must return to its original shape after being stretched.
When lycra doesn't have enough recovery, deformations appear — fabric pockets, excess looseness, and a progressive loss of the leotard's fit.
That's why I always recommend investing in quality lycra. A fabric with good elasticity and recovery makes sewing easier, improves fit, and considerably increases the garment's durability.
My Advice After 20 Years Making Leotards
If I had to give one single piece of advice to someone starting to sew lycra, it would be this: don't obsess over finding special threads.
Use a good lycra, a quality polyester thread, the right needle, and take the time to correctly adjust the tension and zigzag stitch until you achieve that accordion effect that allows the seam to follow the movement of the fabric.
That's the difference between a seam that lasts for years and one that bursts on the very first use.