The Merino Miracle

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Merino wool is one of nature’s little miracles. Naturally breathable and odour resistant, the interior of the fibre is ‘hydrophilic’, meaning it retains water. When merino absorbs perspiration, it holds it in the fibre without the fabric being damp against your skin. The outside of the fibre on the other hand is ‘hydrophobic’, i.e. it repels water. Add to that the fact it also absorbs UV radiation and it’s hard not to be at least a little impressed.

Merino helps regulate your body temperature regardless of the conditions. In the cold, it traps a layer of air against your skin which your body heat then warms, keeping you insulated in the process. However, what a lot people don’t realise is that it is just as versatile in warmer conditions. This is due to the fact that each and every fibre is breathable. So, when you start to produce more heat than the fabric can retain, in the form of moisture, the excess is released through the fibres as vapour and moves away from your body. So, whether riding in winter through wind and rain, or climbing mountains in the height of summer, this ‘super-wool’ works with your body and the conditions you’re facing.

There are, as you might expect, different grades of merino. You can find various grades within Rapha jerseys, boxers, hats, socks, polo shirts, sweatshirts and, of course, base layers. The merino used in Rapha products is the result of a long-running research and development programme set up in New Zealand, home to the world’s finest (and softest) merino sheep.

Combining scientific analysis with state-of-the-art breeding programmes, merino produced under the Merino Advanced Performance Programme (MAPP) is now widely recognised as the very best of an already high-quality fibre. MAPP merino not only guarantees that the wool has been responsibly sourced but also that it will perform better than any synthetic fabric.

And don’t just take our word for it. In studies conducted by the Clothing and Textile Sciences Department at New Zealand’s University of Otago, a group of significantly fitter than average athletes were monitored during a range of exercises in varying conditions. To determine the extent to which the fabric worn when exercising affected performance, the athletes were tested first wearing merino garments and subsequently wearing performance garments made from 100% polyester. In an effort to prove the versatility of MAPP merino, both athletes and garments were tested in both cold and hot conditions, 8C and 32C respectively.

The results were striking. While all the athletes displayed a lower heart rate during periods of exertion wearing merino compared with polyester in cold conditions, their heart rates in hot weather were lower still. Similarly, the onset of sweating happened much sooner when the polyester garments were worn although, interestingly, the difference was more pronounced in cold conditions than hot. Lastly, the percentage increase in core body temperature was lower for the test subjects wearing merino than synthetics, markedly so in hot conditions.




Beats per minute (bpm) one minute intervals throughout exercise using PE4000 Polar heart rate monitor.




Mean minutes to the onset of sweating during exertion, determined by examining the match in time point intervals between a marked increase in core and skin temperature with a corresponding increase in relative humidity under the garment.




Mean core temperature in degrees celsius, one minute intervals using a disposable oesophagael thermistor.



High-grade merino performs significantly better in reducing physiological stress during exercise than its polyester counterparts. The key to the performance of merino produced under the MAPP scheme is the strength and length of the individual fibres. The finer the fibre, the higher the grade of the merino and consequently, the better the performance. MAPP merino uses the finest merino fibres available. This is achieved, in part, by the lifestyle of the sheep that produce the wool. Free to graze on pasture in New Zealand’s mountainous farming terrain, MAPP sheep spend their lives between 2,000 and 7,000ft above sea level – i.e. in very clean air – and in very low concentrations when grazing, thus reducing stress. In merino terms, the sheep produced under MAPP guidelines are the equivalent of wagyu beef.

Rapha have pioneered the resurgence in the use of wool for cycling apparel. Sportwool and Merino are performance fabrics derived from a natural source, and they work with your body and skin like nothing else.

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