Merino Short - 5"
Designed for everyday movement in merino.
Shop nowMerino Wool vs. Cotton: Why One Wins the Gym Performance Test
When moving away from plastic-based gear, most people reach for the most familiar natural fiber: cotton. It’s breathable, soft, and ubiquitous. However, for women navigating the physiological shifts of perimenopause or practicing cycle syncing, the "Cotton vs. Merino" debate isn't just about comfort—it's about how your clothing responds to sweat and sudden temperature spikes. While both are natural, their performance under pressure couldn't be more different.
Moisture Management: The "Wet Towel" Effect
The primary difference between these two fibers lies in how they handle water. Cotton is hydrophilic, meaning it loves liquid. It can absorb up to 25% of its weight in water, but it holds that moisture in the core of the fiber. Once a cotton shirt gets wet from a workout or a hot flash, it stays wet, becomes heavy, and loses its shape.
Merino wool, conversely, manages moisture in its vapor state. It pulls sweat away from the skin before it even turns into liquid. This is critical for activewear for hot flashes, where the goal is to prevent the "drenched" feeling that leads to immediate discomfort and skin irritation.
- Cotton: Absorbs liquid sweat, becomes heavy, sags, and takes hours to dry.
- Merino Wool: Transports moisture vapor, feels dry to the touch even when damp, and maintains its structure.
Temperature Regulation and the Post-Workout Chill
For women in the luteal phase of their cycle or those experiencing menopausal night sweats, body temperature is in constant flux. Cotton provides no thermal buffering. When you sweat in cotton, the fabric becomes a cold, damp layer against your skin. As soon as you stop moving, that moisture evaporates rapidly, causing a dramatic drop in body temperature.
This "flash cooling" is exactly why many find that synthetics fail the Pilates 'rest phase', and cotton performs similarly poorly. Merino wool is a complex protein fiber that provides active thermoregulation. It keeps you cool during a spike and retains just enough warmth during the cooldown to prevent the post-workout shivers.
Odor Resistance and Skin Sensitivity
If you have ever noticed that your gym clothes smell even after a wash, you are likely dealing with bacteria trapped in the fibers. Cotton lacks the natural antimicrobial properties found in wool. Because cotton stays damp, it becomes a breeding ground for odor-causing bacteria and can contribute to "bacne" or clogged pores.
Merino wool contains lanolin and keratin, which are naturally resistant to bacteria. This is why you can often rewear Merino wool activewear without washing it after every session. Furthermore, for those with hormonal skin sensitivities, the ultra-fine fibers of high-quality Merino are often more soothing than the relatively coarse fibers of standard cotton. You can learn more about this in our guide: Can You Wear Merino Workout Tanks If You Have Eczema or Sensitive Skin?
The Verdict: Can You Wear Cotton to the Gym?
While cotton is a "low-tox" alternative to polyester, it is generally unsuitable for high-performance exercise or managing hormonal temperature fluctuations. It fails to move moisture quickly enough to keep the skin dry, leading to chafing, chill, and heavy garments. For a workout wardrobe that supports your endocrine system rather than hindering it, Merino wool offers the technical performance of a synthetic with the health benefits of a natural, plastic-free fiber.
- Best for Low-Impact/Dry: Cotton (Yoga, stretching, light walking).
- Best for High-Intensity/Hormonal Support: Merino Wool (Spin, HIIT, Pilates, and Menopause management).
To understand more about how your fabric choices impact your long-term health, explore our deep dive into the question: Are My Gym Clothes Messing With My Hormones?
