Skip the mirror. Squat.
Good activewear isn’t just tight or just loose. It stays where you put it through your full range of movement, and you find that out with a squat, a reach and a rotation, not by turning sideways under the changing room lights.
The garment has to follow you#
Every piece has three jobs while you move: cover you, stay in place, and not restrict a joint. They fight each other. Cut tight enough to stay put and it can limit a squat. Roomy enough to move freely and it rides up or slides down.
Fit is the balance you pick for your body and your sessions. It’s also personal in ways size charts can’t capture; two people with the same measurements can have very different torso lengths, hip shapes and shoulder widths.
Fabric changes the equation too. A knit with elastane follows your body. A woven with little stretch won’t, and needs a roomier cut. Fit and fiber are one decision.
Four tests, under a minute#
Most fitting rooms have room for these.
Squat. As deep as you can, hold it. The waistband shouldn’t slide, the fabric over the knee shouldn’t pull tight enough to restrict, nothing should go sheer.
Reach. Both arms overhead, then across your body. The top shouldn’t ride up past where you’re comfortable, and the armhole shouldn’t bite the shoulder.
Lunge and side step. Watch for pulling at the hip and a waistband that rolls.
Sit and lean forward on the bench. That’s where a narrow or badly shaped waistband shows itself.
Tops: shoulders, armholes, hems#
The shoulder seam should sit near the end of your shoulder bone, not below it, unless it’s a deliberate drop shoulder. Seam past the shoulder? It’ll restrict an overhead press. Seam well inside it? It pinches. Patagonia’s Houdini windbreaker shows how little a wind layer needs to weigh: 105 g (3.7 oz) for the men’s and 96 g (3.4 oz) for the women’s, about $119 at patagonia.com as of Oct 2026.
The armhole is the detail we check most. A tight, high armhole looks tidy on a hanger and limits the shoulder. Raglan sleeves or a slightly lower armhole give more range. With a racerback or strappy back, make sure the straps don’t press the shoulder blade or the side of the neck as you move.
Hems depend on the session. One that lands at the widest part of the hip rides up when your arms go up. A slightly longer or shaped hem, or one with a light grip, stays put.
Bottoms: rise, waistband, gusset#
Rise, how high the waistband sits, is the biggest fit variable in bottoms, and it’s a function call, not a fashion one. Below the point where your hip creases in a squat, it slides down. At or above the natural waist, it holds, especially in high-movement sessions.
Waistband construction matters more than width. Encased elastic (elastic sewn inside a fabric tube) spreads pressure and resists rolling. Narrow exposed elastic digs in when you sit or fold. A knit band with no elastic relies entirely on fabric recovery, which fades with wear. A drawcord helps only if the band is already close to your size.
Then the gusset, the extra crotch panel in shorts and tights. It removes the seam that would otherwise run through the highest-stress point and adds range. Look for flat seams around it; a raised seam there, you’ll feel on rep one.
Close fit vs compression#
They’re different things. Close fit means the fabric follows your shape without fiddling. Compression means it’s engineered to apply graduated pressure on a limb or the torso, usually with a denser knit and more elastane. Lululemon’s Align High-Rise Pant 25” is a useful reference: its Nulu fabric is 81% nylon and 19% Lycra elastane, and it usually runs $69–$98 depending on sales, per lululemon.com and Fleet Feet, Oct 2026.
Compression has its place, for people who like the feel or have been advised to use it. It isn’t automatically better. Too small restricts movement; too big loses the pressure it was built for. Don’t want compression? A well-cut close-fitting knit beats a poor version of a technical piece.
Length, coverage, opacity#
Tights that stop just below the knee can bunch at the joint. Ankle length can pull when you bend. Shorts with a fitted liner need it long enough to stay clear of the inner thigh, which is why many people want a longer inseam for running than lifting.
Opacity is part fabric weight, part stretch. A thin knit over a bent knee or folded hip can go see-through. Test it: bend, hold, and look at the fabric against the light in a well-lit room.
Size up, never size down#
Size up when a garment restricts you: armhole limits your reach, waistband won’t stay put, fabric goes tight enough to shine and turn sheer. The next size in a well-cut piece is usually still close-fitting.
Don’t size down to make a knit feel tighter than it was built to. That overstretches the elastane, so recovery goes faster, and it strains seams not designed for it. Garments bought too small tend to fail at the seams first.
Red flags you can spot now#
A waistband that rolls the moment you bend will keep rolling. Fabric that springs back slowly after a stretch has weak recovery. A hem that flips when you lift your arms will flip in the gym. A shoulder seam off your shoulder won’t settle later.
See any of these and no adjusting will fix it. Back on the rail.
Two minutes of real movement teaches you more than ten minutes of looking. Fit is the difference between wearing something thirty times and three, and you can judge it for free before paying.