Indoor-Cycling underwear at Bobshop
For indoor training, the question is whether a base layer makes sense at all. The answer depends on how much you sweat and how well the room is ventilated.
An extra layer without headwind
Outdoors, the base layer has two tasks: it transports moisture away and keeps the skin away from the wet jersey. On the trainer, the second point does not apply, because nothing dries anyway. What remains is moisture transport, and that only works with very thin, open fabrics.
Many people train indoors without a base layer, only in a jersey or top. This is acceptable as long as a fan provides air movement. Without a fan, the thinnest available layer helps more than none, because it draws sweat away from the skin.
For sessions of several hours on the trainer, it is worth changing in between. A dry top after two hours changes how you feel considerably and prevents the second half from failing because of the clothing rather than your form.
A fan changes training more than any item of clothing. Place it directly in front of you at upper body height.
