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Race Science

The Speedsuit Buys You Seconds. The First 400 Meters Buy You Minutes.

A swim skin saves a non-wetsuit racer maybe 20 seconds. Swimming the start too hard can cost you minutes — on the bike and run, where your race is actually decided.

Race Science · 6 min read
A 70.3, by time Where the speedsuit helps — and where a blown-up swim makes you pay Swim ~10% Bike ~53% Run ~37% Speedsuit: ~20 s here A too-hard swim taxes here: ~4% of your bike, carried into the run The suit works on the smallest leg. The pacing mistake is paid on the two biggest. Times are illustrative for a ~5:30 finisher; the ~4% cycling-efficiency loss is peer-reviewed.
The speedsuit helps in the 10%. Pacing protects the 90%.

Before a warm-water race, the gear question every age-grouper asks is whether to buy a swim skin. It is the suit the pros wear when the water is too warm for a wetsuit, a thin, snug second skin that promises free speed in the one leg most triathletes dread. It is also, mostly, the wrong thing to be thinking about, because the swim is the leg where the biggest gain on offer is not a purchase at all.

Take the suit on its own terms first. A swim skin is worn over your race kit when the water is above wetsuit-legal temperature, and it is explicitly banned from providing any buoyancy, so unlike a wetsuit it cannot lift your legs and flatten your body. All it does is reduce surface drag and squeeze you a little. When researchers measured national-team triathletes in a flume, the speedsuits cut swim time about 1.5 percent, which over a half-distance swim works out to somewhere between 15 and 45 seconds. Subtract the ten or fifteen seconds it takes to peel the thing off in transition and the real-world gain is more like 15 to 30 seconds. It costs between $150 and $315, and the fabric wears out. That is a genuine benefit, and it is a small one. Notice, too, that the brands sell these suits with stories about how many pros wore them, not with a number of seconds. There is a reason for that.

Now the other side of the ledger, which is where the surprise lives. Researchers took trained triathletes and had them swim the same race three ways, controlled, hard, and all-out, then ride and run as fast as they could. The all-out swim did not just leave them tired in the water. It made the entire triathlon significantly slower than the controlled swim, and the damage showed up on the bike, where cycling efficiency dropped by about four percent. Go out too hard and you climb onto the bike with lactate elevated, heart rate and breathing spiked, and a body that can take twenty to thirty minutes to find its normal power, on a leg that is half your race. The seconds you stole in the water get repaid, with heavy interest, over the next several hours.

Put the two next to each other and the trade is lopsided. In a 70.3 the swim is only about ten percent of your total time. Spending everything you have to gain a handful of seconds in the smallest leg, and paying for it across the two biggest, is one of the worst exchanges in the sport. The speedsuit buys you seconds inside that ten percent. Pacing the first 400 meters protects the ninety percent that follows. One of those is a purchase that helps you once. The other is a free skill that helps you in every race you ever start.

So how do you swim it. You start controlled and build, over the first few hundred meters, while every instinct and every churning body around you screams to sprint. The adrenaline at the gun feels exactly like fitness and is not. For a 70.3, hold something like 85 to 90 percent of your hardest sustainable effort; for a full, a little less. The entire discipline lives in the first two minutes, before the field settles, and it is the cheapest minutes you will ever buy back.

None of this means the suit is pointless, and the honest version says so. If your race bans wetsuits, wear the skin, because twenty free seconds is still twenty seconds, and pacing and a speedsuit are not an either-or. There is even a wrinkle at the short end: for trained athletes racing a sprint, a faster swim has been shown to help, so the ease-in rule is really a long-course rule. The point is not that the speedsuit is a waste. It is that if you can only master one thing in the water, master the pacing, because the suit is worth seconds and the pacing is worth minutes.

Buy the speedsuit if your race demands it, then forget about it and go practice swimming the first 400 meters under control. The suit saves you once, in the smallest leg of the day. The pacing saves you every time, in the two legs where the race is actually won and lost.

The takeaways

  • A swim skin saves a non-wetsuit racer about 1.5 percent, roughly 15 to 30 seconds net after stripping it in transition. It has no buoyancy, so it's about a third of a wetsuit's benefit, and it costs $150 to $315.
  • Swimming the start too hard made the whole triathlon significantly slower in a controlled study, mostly by cutting cycling efficiency about four percent. You start the bike over-cooked and can take 20 to 30 minutes to recover normal power.
  • The swim is only ~10 percent of a 70.3. Blowing it up to gain seconds there, and paying minutes across the bike and run, is a losing trade.
  • Swim it controlled and build over the first few hundred meters; the adrenaline at the gun feels like fitness and isn't. Hold ~85 to 90 percent for a 70.3.
  • It isn't either-or: wear the skin if your race bans wetsuits. But if you master one thing in the water, master pacing — the suit buys seconds and the pacing protects minutes.

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