Why Activewear Shrinks and How to Stop It

When activewear shrinks, heat is almost always the cause, not the movement or the washing itself. The elastane and synthetic fibres that give leggings their stretch break down under high temperature, and the knit tightens. The fix is purely thermal: keep the heat out of the care routine.

What heat does to the fibres

• Tumble dryers cook the elastic until it loses spring.
• Hot washes relax the knit and let it contract.
• High heat sets a smaller shape permanently.
• Repeated heat cycling compounds the shrink.
• Ironing activewear can melt or tighten it.

The fibres are engineered to return to shape, but heat overrides that memory. Once elastane is heat-damaged, the garment stays smaller and the recovery is gone. Cold water and air drying preserve both the size and the stretch.

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Silk Cashmere Cropped Heat Wave Tank

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A no-shrink routine

1. 01Wash in cold water only.
2. 02Skip the tumble dryer; air dry flat or hanging.
3. 03Keep activewear away from radiators and direct heat.
4. 04Never iron leggings or technical tops.
5. 05Reshape while damp to hold the cut.

What to check before you buy for activewear shrinkage

Two pieces can look identical on the hanger and behave differently in activewear shrinkage. The checks below are the ones that catch it early. Grey ALO Runner (Unisex) is the piece we would test them against first.

• Try it in the position you will actually hold, not standing straight.
• Check the seams against your skin — a flat seam only rubs after twenty minutes.
• Wash it once before you judge the fit; knit relaxes about half a size.

If it already shrank

Mild heat shrink can partly relax with a cold soak and gentle stretch while damp, but true elastic damage does not reverse. The reliable move is to replace the piece and change the routine so the next one lasts.