Training apparel is sold on a small vocabulary of claims, and they mean quite different things. Some are measurable and appear on the label; others are descriptions of a knit structure that anyone can apply.
Moisture wicking is a structure, not a coating
Synthetic fibres do not absorb water. What a wicking fabric does is move sweat along the fibre surface and spread it across a wide area so it evaporates faster. That is a function of the knit and the fibre cross-section, and it does not wash out.
This is why a polyester training top feels dry faster than cotton even when it holds a similar amount of water. Cotton absorbs into the fibre and stays wet.
Compression: measurable pressure, modest claims
True compression garments apply graduated pressure, measured in mmHg, and have documented effects on perceived soreness and on how limbs feel afterwards. The evidence for improved performance during exercise is much weaker than the marketing.
Most "compression" training tops are simply tight-fitting. That is not a criticism - a close fit under a layer is genuinely more comfortable - but it is a fit description rather than a medical one.
UPF is a rating, and it is checkable
UPF 50+ is a tested rating meaning the fabric transmits less than one fiftieth of UV. It depends on knit density, colour and fibre, and it degrades as fabric stretches or wears thin.
A stated UPF rating on a listing is a real specification. "Sun protective" without a number is not. For long outdoor sessions, the rated garment is worth the difference.
Odour control and what actually causes smell
Bacteria feeding on sweat cause odour, and synthetics hold onto those bacteria more than natural fibres. Silver-ion and similar treatments reduce it and wash out over time. Merino blends resist it inherently and cost more.
The most effective intervention is not leaving a wet top in a bag. Odour that has set into a synthetic garment is very difficult to remove afterwards.
Seams are where a training top fails
Flatlock seams lie flat against skin and do not chafe; overlocked seams stand proud and will, over a long session. Under a pack or a harness, this is the specification that decides whether a garment is wearable for two hours.
Look for seam placement away from the shoulder line if anything will be carried.
Fit and layering
A base layer should be close to the skin to wick; a loose top over it holds air and slows evaporation. Wearing a loose wicking shirt on its own works well in dry heat and less well in humidity.
Sizing on athletic tops runs closer than casual sizing. The manufacturer's chest measurement is the number to read.
Washing rules that matter
No fabric softener - it coats fibres and destroys wicking, which is the most common way a good training top stops working. Cool wash, and no tumble drying on synthetics with elastane, which loses recovery with heat.
Wash separately from towels, which shed lint that clogs technical fabrics.
Multi-packs and honest use
Four-packs of training shirts are good value if the fit works. Buying one first and then the pack is slower and much cheaper than buying four that do not fit.
Rotate them rather than wearing a favourite repeatedly. Elastane recovers with rest and lasts longer for it.
What we publish
Fibre composition, seam type, UPF rating where the maker has tested it, and the manufacturer's size range. Those four cover the questions worth asking, and they separate a specification from a description.