What a Wetsuit Actually Does to Your Stroke.

She came out of the lake after four hundred metres with her shoulders burning, convinced she had lost fitness over the winter. In the pool, that morning, she had swum a comfortable set of hundreds and her shoulders had not registered at all.

Nothing had gone backwards. She had just put on a wetsuit for the first time since September and swum in it as though it were not there.

A wetsuit is not a neutral layer that keeps you warm. It changes your body position, your drag, your stroke rate and what your shoulders have to do, and if you have not accounted for that, the first time you find out is in open water with a race number on your arm.

The suit gives you your legs and takes your shoulders. Whether that is a good trade depends entirely on what your stroke looked like before you put it on.

What It Gives You

The neoprene is not the same thickness everywhere, and that is the whole design. The panels through the core and the legs are thick, often up to five millimetres. The arms and shoulders are thin, commonly one and a half to two.

That distribution does one job: it lifts your hips and legs toward the surface and puts your body flat. Form drag, the resistance created by your shape ploughing through water rather than slipping along it, falls sharply. Studies going back decades have reported drag reductions in the region of twelve to fourteen per cent, and velocity gains for the same effort somewhere around three to ten.

Which is a very large range, and the reason for the range is the most useful thing in this article.

The Benefit Goes to the Swimmer Who Needs It Most

The wetsuit effect is not distributed evenly. It is largest for swimmers with poor natural buoyancy and inefficient body position, swimming at slower speeds, and smallest for efficient swimmers who already lie flat in the water.

Read that again if you are a strong swimmer, because it explains something that annoys you every June. The suit is doing very little for you and a great deal for the person you used to put four minutes into. Neoprene compresses the field. If your swim is your weapon, a wetsuit-legal race blunts it, and you should plan the day accordingly rather than being surprised by it.

And if you are the sinking-legs swimmer who has been told for two years to fix your body position, the suit will paper over that beautifully for ninety minutes a year and do nothing for you the rest of the time. Take the free speed on race day. Do not let it stop you fixing the shape.

What It Takes Away

Every wetsuit is a compromise between buoyancy in the middle and freedom at the top, and no amount of marketing dissolves that. Even good suits with thin, flexible shoulder panels add resistance to the recovery and to the internal rotation of the shoulder.

The effect is small per stroke and you take somewhere around six hundred strokes in an Olympic distance swim. That is where the burning comes from. It is not fitness and it is not the cold. It is a slightly more expensive stroke, repeated several hundred times, in a shoulder that has done all of its winter work unrestricted.

Two things follow. A suit that is too tight across the chest and shoulders will cost you more than the buoyancy gives you, which is why fit beats price and why a cheap suit that fits your shoulders beats an expensive one that does not. And you have to condition for it, which means swimming in the suit before race day rather than pulling it out of the bag on the morning.

What It Changes About How You Swim

Three things change, and none of them are obvious until somebody says them out loud.

Your kick matters less. The suit is doing the job your kick was doing, which is holding your legs up. Keep it small and steady, two beats, and use it for rhythm and balance rather than propulsion. Kicking hard in a wetsuit is a superb way to arrive at T1 with nothing left for the bike, and it buys you almost no speed.

Your stroke rate tends to rise. Sitting higher with less drag, most swimmers naturally turn the arms over quicker. That is usually fine and often faster. What it means is that the long, gliding stroke you have been rehearsing in the pool is not the stroke you will swim, and if you have only ever practised at pool rhythm you will feel out of time.

The catch feels different. You are higher in the water, so the position where your hand finds pressure sits differently. Nothing about the mechanics changes, but the feel does, and feel is what you are navigating by out there.

All of which is a long way of saying that your pool stroke does not survive first contact with neoprene, and the fix is not technical. It is exposure.

The Practical Bits Nobody Tells You

Swim in the suit at least three or four times before you race in it, and at least once at genuine race effort rather than a gentle paddle. Effort is what exposes the shoulder cost.

Spend ten minutes getting it on properly. Almost everybody wears their suit too low. Work it up the legs in stages, then get the crotch as high as it will go before you touch the arms, then pull the torso up hard so the shoulder panels sit where they were designed to. A suit worn low leaves a pocket of water in the seat and drags your hips back down, which undoes the one thing you bought it for.

Lubricant on the neck, wrists and ankles. The neck because a rubbed raw neck is genuinely miserable for a week, the wrists and ankles because they decide how fast you get out of the thing in T1.

And practise the removal. Unzip and strip to the waist while you are running, not standing still. There are two minutes sitting there for anybody willing to look slightly foolish in a car park a few times.

Sizing, and Why Most People Buy the Wrong One

Wetsuit sizing runs off height and weight, and the two rarely agree with each other. When they conflict, go with the chart's shoulder and chest fit rather than the leg length. A suit an inch short in the leg costs you nothing. A suit that restricts your chest costs you your race, because you will feel like you cannot get a full breath in the first four hundred metres, and in cold water with a start line full of people that is how panic begins.

A correctly fitting suit should feel genuinely tight on land, tight enough that you doubt it, with no loose folds at the lower back or behind the knees. Those folds fill with water. What it must not do is restrict your ability to bring both arms overhead and hold them there comfortably.

Try it wet if a shop will let you, because neoprene behaves differently once it is soaked, and if you are buying online buy from somewhere with a swim-and-return policy. This is not a garment you can assess in a hallway.

When You Cannot Wear One

Plan for it, because the decision is made on the morning and it is not made by you. Most governing bodies set a temperature above which wetsuits are banned, and a swim you have rehearsed exclusively in neoprene becomes a genuinely different event without it.

Your hips drop. The stroke you have grooved for months, built on legs that were being held up for you, suddenly needs a kick again and a core that holds position. Swimmers who never swim without the suit find this out three hundred metres into a race in unusually warm water, and it is one of the more reliable ways to have a very long morning.

So swim some of your open water sessions in a swimming costume when the temperature allows it. It is colder and slower and less pleasant, and it keeps the underlying stroke honest, which is the thing the suit was quietly letting you avoid.

The Challenge

Get the suit out this week, before the water gets cold enough to make it a chore, and swim four hundred metres in it at the effort you intend to race at.

Count your strokes for one length and see how it compares with the pool. Notice where the shoulders start to talk.

That is the information you were going to collect on race morning otherwise, at considerably greater expense.