Look here, it’s about your... Well, it’s about your polyester base layer... How can we put this nicely..? Sorry, there’s no two ways about it, no beating about the bush, we’ll just have to come right out and say it:

Yeeeuw. That whiffs!

No, it’s not you. It’s your base layer. And your bacteria.

So why is it man-made base layers stink so bad after wearing them a few times? It’s all down to chemistry. Petro-chemistry, that is.

Man-made base layers are all made from oil. They’ve got some good things going for them,

So how come they smell so fast too? The problem is, though they claim to be breathable, it’s only the holes in the weave of the fabric that breathe, not the fabric itself.

At rest, the body may lose half a litre of water per day through perspiration. Riding hard up a mountain, that can rise to one litre an hour. The job of a base layer is to get that perspiration away from the body fast. The problem with a man-made fibre is that it can only absorb up to 5% of its weight in moisture. (No wonder it dries fast.)

Meanwhile, back under the stink-layer, things are hotting up. The sweat that can’t get away is condensing on the skin and the bacteria can start to get to work. The synthetic fibres are a playground for bacteria because the fibres are so uniform and easy to cling to. They soon set up camp, light a fire and make lunch.

Merino fibres, on the other hand, are coated with microscopic scales that make it hard for the bacteria to grab hold of, proving once again nature is much smarter than man.

And those heavy-metal particles you haven’t sweated off onto your skin are washed into the water supply.

And that stinks too, no?