Most wetsuit sizing advice answers one question: how should this suit fit on race morning? That's a fine question if you're buying a wetsuit you'll wear twice a year. It's the wrong question for the Blue70 Reaction, a suit built for swimmers who train in open water week after week, often for an hour or more at a stretch.
Blue70 positions Reaction, priced at $680, for exactly that swimmer. It uses a higher grade of Yamamoto neoprene than the Fusion and is recommended for frequent, longer training sessions rather than occasional race use. A suit you'll pull on and off fifty or a hundred times this year needs a different fit standard than one you'll wear once. Here's how to think about sizing when you're buying for a season, not a single event.
Training Fit Is a Different Problem Than Race-Day Fit
A race-day suit has one job: feel right for one swim, on one morning, when adrenaline does a lot of the heavy lifting anyway. A training suit has to feel right on swim thirty, when the neoprene has softened a little, your shoulders are tired from three earlier sessions that week, and you're rushing to get in the water before practice starts.
That repetition changes how small compromises add up. A slightly tight shoulder might be tolerable for a 40-minute race. Across a season of two-hour training swims, the same restriction shows up in your stroke count, your fatigue, and eventually in a suit that chafes at the neck by week six. Sizing with only race day in mind can leave a training swimmer stuck with exactly that problem.
Snug on Land, Better in the Water
Every fitting conversation eventually lands on the same rule. A wetsuit should feel snug standing on dry land. It should feel noticeably better once you're moving in the water. Swimmers who size up because a suit feels tight in the living room are almost always making the wrong call.
The physics is simple enough. Standing upright, gravity pulls straight down and a snug suit feels exactly like that: snug. Once you're horizontal and submerged, water supports your weight and spreads pressure differently across the neoprene. A suit sized correctly on land settles into a comfortable, supportive fit once you're swimming. A suit that already felt loose on land stays loose in the water, and loose neoprene means water flushing in and out with every stroke, which works against the insulation the suit is supposed to give you.
This matters more for a training suit than a race suit for one reason. You'll run this check dozens of times over a season, not once. Second-guess the snugness every time you pull the suit on, and the temptation to size up "for comfort" grows. Resist it. A suit that never fully commits to snug will never settle the way it's built to.
What Reaction's Construction Means for Your Fit Check
Reaction uses Yamamoto neoprene with higher cell-count, more flexible panels through the shoulders and upper arms, where mobility matters most for the catch and pull. The torso and legs get denser, more structured panels, where stability and durability matter more than stretch. That split changes what you're actually testing at each part of your body.
At the shoulders, check range of motion through a full stroke cycle, not standing arm circles. Reach one arm overhead like you're starting a catch, then rotate through to where your hand would exit near your hip. If the neoprene fights you or bunches under the armpit, that's worth solving before you commit, because shoulder restriction compounds over a long swim in a way it never does over a short pool set.
Through the torso, the denser panels do more of the structural work. Too loose, and you'll feel water moving with every stroke. Too tight, and you'll feel it on the rotation and the breath. Neither is something you want to discover forty minutes into an open water swim, well past the halfway point.
Measure Before You Check the Size Chart
Height and weight alone rarely tell the whole story. Torso length and limb length vary independently of both, and two swimmers with identical height and weight can have very different proportions.
Before checking Blue70's size chart, take three additional measurements:
- Chest circumference at its fullest point
- Waist circumference at the navel
- Hip circumference at its widest point
If your chest and hip numbers point toward different sizes, that's useful information, not a problem. It tells you exactly where to focus attention during a test swim and which compromise you're weighing. Blue70's sizing tool and size charts are built around these measurements, and they're worth using even if you've owned a wetsuit before. Reaction's cut isn't identical to every other model in the lineup.
How a Season Changes the Fit
Neoprene isn't static once it's in use. Repeated stretching, sun exposure, and the ordinary mechanical wear of being pulled over damp skin soften the material gradually across a season. A suit that fits snugly at swim one usually feels a bit more accommodating by swim thirty, with no change to your body at all.
That's an argument for buying the correct fit now, not for sizing down and hoping a break-in period bails you out. A suit too tight on day one to allow a full catch motion won't magically become race-ready by midseason. It'll just stay uncomfortably tight longer. Size for the standard above, snug on land, better in the water, and let the natural softening work in your favor.
Care matters just as much as sizing. Reaction holds up to frequent training use when it's rinsed in fresh water after saltwater or chlorine exposure, dried away from direct sun, and stored unfolded. Blue70's one-year warranty covers manufacturing defects in materials for the original owner, but it doesn't cover fingernail punctures, heel tears from a rushed donning process, zipper damage from forcing a stuck zip, or damage from non-swimming use like surfing or kayaking. Most of that damage is preventable with a consistent donning habit: bunch the neoprene at the wrist and ankle before pulling it up, and never drag a fingernail across a panel to adjust it.
Stuck Between Two Sizes?
Lean toward the size that preserves shoulder mobility, even if it means slightly more room through the torso. A looser torso costs you a little thermal efficiency and a bit more water movement in and out of the suit. A restricted shoulder costs you stroke mechanics on every swim for as long as you own the suit.
For a suit worn once on race morning, a swimmer might reasonably accept more shoulder restriction in exchange for a tighter, more streamlined torso. For a suit worn weekly across a full training season, that trade-off should usually run the other way.
Femme Fit Sizing on Reaction
Every women's Blue70 wetsuit, Reaction included, is built on Femme Fit sizing rather than a scaled-down men's pattern. That means refined shaping through the bust, torso, wrists, and ankles, a lowered neckline for comfort and reduced chafing, and an extended zipper opening that makes donning and race-day transitions easier.
Women who've worn a unisex-pattern wetsuit before and found the torso too long or the shoulder seams misaligned should expect a different experience with Femme Fit sizing. Measure and size independently. Don't assume the number that worked in a men's suit will translate directly.
Closing the Gap Between Guesswork and Certainty
Sizing a wetsuit from measurements and a chart is educated guesswork, even with good numbers in hand. That's exactly why Blue70's Test Swim policy exists. You can swim in the wetsuit and still return or exchange it within 30 days, as long as it comes back clean, dry, and with tags and accessories intact.
Use it. Get into open water or a pool wearing the suit the way you'd actually train in it. Run through a real warm-up, add a harder effort segment, and judge the fit under real swimming conditions rather than a few arm circles in front of a mirror.
A training wetsuit is a season-long relationship. Measure carefully, favor shoulder mobility when you're caught between sizes, and trust the snug-on-land rule even when it feels wrong standing in your kitchen. Get that right, and the suit disappears into the background of your training, which is exactly where you want it.
