Pilates and reformer work need grip and coverage more than support. You are upside down, side on and folded, so a top that stays down and leggings that do not go sheer in a deep squat matter more than compression. Running is the opposite: it is repetitive vertical impact, so bra support is the whole question, and fabric needs to move sweat rather than hold it. Lifting sits in between. You want a bra that stays put under load, fabric that survives a bar on the back or hips, and a waistband that does not roll when you hinge. The single most common mistake is buying one bra and using it for all three. A light-support bralette that is perfect on a reformer will not hold up over five miles, and a high-impact running bra is unnecessarily rigid for mat work.

Do the squat test in the changing room every time, in the light, because opacity varies by colour and by how much the fabric has been stretched. Look for a fabric with some weight, since ultra-light leggings feel excellent for twenty minutes and go transparent under tension. Flat-locked seams sit smoother under a bar and under a waistband. On bras, check the band rather than the cups: a firm band does most of the support work, and if you can pull it more than a couple of inches away from your back, it is too loose. Straps that adjust are worth the small extra cost. Natural blends with a little elastane are more comfortable next to skin and hold odour less than pure synthetics, but they stretch out faster, so use them for lower-impact work and keep the technical synthetics for running.

Two bras at different support levels, two leggings, one pair of shorts and two tops will cover most weeks. Add one sweatshirt or hoodie that is not technical fabric, because the thing you wear before and after is the thing you spend the most time in. Wash activewear cold, without fabric softener, which coats the fibres and destroys wicking, and hang to dry rather than tumbling, because heat kills elastane. Rotate bras rather than wearing the same one daily, since the elastic needs time to recover its shape. Replace a running bra when the band stops feeling firm, typically after a year or so of regular use, not when it looks worn out. And keep one set genuinely for the gym rather than letting it drift into daily wear, which is what wears kit out fastest.

Spend on the bra and save on the leggings. The bra is the piece that determines whether a workout is comfortable and it is the piece that wears out on a schedule. Most people do the opposite and own six pairs of leggings and one tired bra. Do not buy the sheer lightweight leggings for lifting, and do not buy the heavily compressive ones for a hot yoga class. Skip anything that needs constant adjusting, because you will stop wearing it within a month. If you take one thing away: buy for the activity you actually do most often, not the one you have been meaning to start.