Merino vs. Bamboo Activewear: Which is Actually Better?

The short answer

Merino wool is the superior technical choice. While both are marketed as "natural," most bamboo activewear is actually Bamboo Viscose—a semi-synthetic fiber created through a heavy chemical process. Merino is a protein fiber that naturally manages odour, regulates temperature, and maintains its shape. Bamboo often loses its structure when wet and relies on chemical treatments to match the antimicrobial properties that Merino possesses naturally.

1. The "Natural" Myth: Viscose vs. Protein Fiber

Bamboo starts as a plant, but to become a soft fabric, it must be dissolved in harsh solvents like carbon disulfide and spun into viscose (rayon). This makes it a "regenerated" fiber rather than a purely natural one. Merino wool, however, is a keratin-based protein fiber that grows naturally on sheep and requires no chemical restructuring to become yarn.

External Resource: The FTC’s guide on Bamboo textiles clarifies that most "bamboo" is actually rayon produced with hazardous chemicals.

2. Performance in Motion: Moisture vs. Vapour

Bamboo is highly absorbent, which sounds good until you start sweating. It holds onto liquid water, becoming heavy, saggy, and slow to dry—often taking twice as long as Merino. Merino wool works on a vapour level, absorbing moisture before it even turns into liquid sweat, keeping you drier and lighter during high-intensity movement.

3. Odour Resistance: Natural vs. Treated

Merino wool is naturally antimicrobial due to the structure of its fibers and the presence of lanolin traces, which prevent bacteria from taking hold. Because bamboo viscose is a smooth, extruded fiber, it lacks this natural defense. Many bamboo brands must add chemical antimicrobial finishes to prevent the "wet dog" or "gym sweat" smell that develops in damp plant-based fibers.

Scientific Insight: Research in the Nature Scientific Reports highlights how protein-based fibers like wool inherently inhibit bacterial growth more effectively than regenerated cellulose fibers.

4. Durability and Lifecycle

Bamboo viscose fibers are significantly weaker when wet, leading to pilling and "bagging out" over time. Merino wool fibers have a natural 3D crimp that acts like a spring, allowing the garment to stretch and return to its original shape for years, especially when reinforced with a small percentage of elastane.