Swimrun Paddles -
The Scientific Evidence

Updated January 2025

Swimrun Paddles are pretty much essential items for most swimrun events. Having said that, I used webbed neoprene gloves for my first event as I was not confident enough to use hand paddles in a race. But after that, I changed over to some green Speedo paddles with a bigger surface area.

"BUT WHERE'S THE SCIENCE?" I hear you ask. "WHAT IS THE RESEARCH EVIDENCE BEHIND SWIM PADDLES?"

To be honest, there hasn't been a lot of reliable scientific research into the optimal size and shape of swimrun paddles. BUT there has been enough research to make an informed choice about the best paddles for YOU!

There are THREE things to look at; The surface area of the paddle, the curvature of the paddle, and the outline of the paddle in plan view (ie looking down from above).

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Two Swimrun competitors swimming together at Ötillö Engadin in Switzerland, wearing green tops and caps.

Neoprene webbed gloves - not as crazy as might first appear - Even a small increase in surface area is effective!

Why use Swimrun paddles?

SURFACE AREA.

A paper (1) published in the Journal of Strength and Conditioning Research investigated how hand paddle surface area affects the metabolic cost of transport (COT), arm cadence, distance per stroke, Vo2 and Heart Rate, while swimming.

Metabolic cost of transport (COT) is defined as the energy required to move 1 kg of body mass 1 meter in both swimming and running.

The use of hand paddles decreased COT, cadence, Vo2, and HR, and increased distance per stroke. In this study, 5 sizes of hand paddles were tested; 201cm2, 256cm2, 310cm2, 358cm2, and 391cm2.

As paddle size increased, so did the benefits - up to a point.

The study concluded that; "The magnitude of the change of COT decreased as paddle size increased, indicating diminishing marginal return with increasing paddle surface area. The largest-sized paddles actually increased COT per stroke compared to swimming without paddles (p = 0.001). Therefore, results from this study suggest that an optimal hand paddle size exists (210–358 cm2) for proficient, adult swimmers, which reduces COT without increasing COT per stroke."

In other words, when it comes to paddle size, there is a Law of Diminishing Returns; Simply going for paddles with a large surface area can be counter-productive.

The OPTIMAL paddle size lies between 210 cm2 and 350 cm2, depending on the hand size of the individual swimmer.

BASICALLY, YOU CAN FORGET ANY PADDLE WITH A SURFACE AREA OVER 350cm2 ! And if you are female or have smaller hands, the most efficient paddles will be more like 270cm2. It looks like the optimal solution is to find a paddle that increases your natural hand surface area by about 70%.

An underwater photo of a swimrun competitor using hand paddles in shallow water.

Underwater shot of swimrun paddles in action!

SHAPE.

BUT there's more to it than just the surface area. What about the shape?

There are 2 ways to consider the shape:

The 3-dimensional shape. Is the paddle a flat board or does it have 3D curvature?
The shape in plan view (ie from above). Does it have a smooth outline like a ship's propeller, or does it have sharp corners?

Let's look at these features, and the science, one by one.

In 2022, Jessica Hargreaves published a paper titled "The effect of the curvature of a swimming paddle on the propulsion force." (2). She studied the relative fluid resistance forces generated by 4 different paddles of equal surface area, differing only in the curvature of the paddle. The curvatures were 0 degrees (ie flat), 10 degrees, 20 degrees and 30 degrees.

The results clearly showed an optimal angle of curvature of around 20 degrees. Increasing the curvature beyond 20 degrees resulted in lower fluid resistance force.

CONCLUSION; Flat paddles are NOT optimal for fluid resistance and therefore generating force.

OUTLINE (PLAN VIEW).

You may have noticed that ship's propellers have rounded edges and outlines, without sharp edges or corners. The reason for this is that sharp edges or corners can induce tip vortex cavitation, where the forces generated at the sharp edge cause the formation of vapour-filled cavities (bubbles). Once cavities form, there is a loss of force on the surface. This means less propulsion!

SO, the optimal outline shape for a swim paddle is smooth and rounded, NOT sharp corners with straight edges between the edges.

IN SUMMARY, the optimal paddles should increase your natural hand surface area by around 70%, which for most people will be 270 cm2 to 350 cm2; the paddles should have a 3D curvature of around 20 degrees; and they should have a smooth, rounded outline when viewed from above. Think of the most efficient shape in the sea - the porpoise!

WHEN LOOKING AT SWIMRUN PADDLES, REMEMBER THESE THREE IMPORTANT FEATURES.

Swimrun Paddles - Running

Remember, you have to carry the paddles while you are running. In all Swimrun events, you have to cross the finish line with ALL the equipment that you started with. So you can't throw the paddles away mid-race if you get fed up with them!

There are 3 ways of running with your paddles;

If your paddles have a wrist strap, you can take your paddles off your fingers and flip them around against the backs of your hands while running.
You can take your paddles off entirely, and stuff them down the front of your wetsuit, after unzipping the front of your wetsuit a little.
Some swimrunners take their paddles off and loop them through their Swimrun belt, usually at the back. The disadvantage here is that the paddles flap around against your buttocks as you are running!

But what do paddles look like? Here are some photos of my current paddles, from Speedo. I like them because they are the correct size for my hands, they have a smooth curved outline, and they have a curved 3D profile!

What about holes in your paddles? What's the scientific evidence for holes v. no holes? It is actually better to have a number of small holes on the surface of the paddle, because this induces a small degree of turbulance which increases the hydrodynamic force generated by the paddle! (3).

Two green swimrun paddles lying on a black surface.

SwimRun Paddles on my kitchen top

Two green SwimRun Paddles lying on a black surface, with a man's hand in the straps of the left one.

SwimRun Paddle on my left hand

Side view of a man's hand in the straps of a green swimrun paddle

SwimRun Paddle on my left hand

I have since replaced the black rubber straps with softer rubber tubing, in a different layout. You can see what I've done in the photos below. The new layout and softer rubber tubing allows me to turn the paddles round quickly when exiting the water, allowing me to use my hands without the paddles falling off.

A green Swimrun paddle with yellow rubber straps

The new rubber tubing straps

A green swimrun paddle with a man's hand inside the yellow rubber straps.

How it works!

A man's hand with a green swimrun paddle flipped around so that only one strap loops around his wrist.

Paddles turned around to allow hand use.

You can find a good deal on the Speedo Swimrun paddles HERE on Amazon.

Swimrun Paddles

And here are some photos of the swimrun paddles that Mogsy is now using. They are a bit smaller than mine, and they are flat (bad), but they are the correct size for her hand!

Mogsy's swimrun paddle

Side view of a black Swimrun paddle for ladies

Mogsy's swimrun paddle - right hand

A woman's hand inside the straps of a black swimrun paddle for ladies

Mogsy's swimrun paddle

GETTING BACK TO THE "WHY" - how much faster can you go? When I talked to several other experienced swimrunners, they all estimated that they could swim faster by about one minute per 1000 meters. AT LEAST. So if you have an event with several swims adding up to 5 kilometers or more, that's a 5 minute difference! MINIMUM! So definitely worth swimming with paddles.

BUT here's my tip; it's more effort to swim with paddles, so you MUST train for it. During your pool sessions (which should be based around speedwork/repetitions), you should wear the paddles for at least 75% of the session.

And in your open water swim sessions, be it lake or sea, you should wear your paddles for the entire swim. It MUST become second nature to swim with paddles!

A green Swimrun paddle with yellow rubber straps and cut-off times written on the inside with black ink.

Cut-off times for the Isles of Scilly event

A handy trick for longer events is to write the cut-off times for each timing station inside your paddle - assuming you don't have black paddles!

Here are a couple of links to paddles available on Amazon that have been recommended by our readers:

Arena Vortex Evolution Hand Paddles

Arena Vortex Swim Training Paddles

Arena Vortex Evolution Swim Training Hand Paddle - CLICK HERE for the best price on Amazon.

Speedo Power Plus Paddle

Speedo Power Plus Paddles

Speedo Power Plus Paddle - CLICK HERE for the best price on Amazon.

The latest paddle design is the Ark Sports Carbon Blades. As the name suggests, these are made of carbon fibre, which means they are very stiff, very light (70 grams) and very thin (1mm).

ARK Carbon Air Rocket with flat design, straight edges, sharp corners, no holes, and a surface area of 465cm2

Obviously, lightness is a desirable asset, but we are not sure about the stiffness. Conventional paddles seem plenty stiff enough, and we have concerns about the sharp corners and straight edges on the paddles inducing tip vortex cavitation.

I have asked Ark about cavitation issues, but have not received a reply.

SO, Swimrun paddles are ESSENTIAL to use, but you have to train with them a LOT beforehand! If you are entering your FIRST swimrun event, DO NOT feel that you HAVE to use paddles, especially in a sprint event - say under 15km (9 miles total). The shorter the event, the less you NEED paddles, and the MORE you need to concentrate on your running!

References;

1. ENERGETICS OF SWIMMING WITH HAND PADDLES OF DIFFERENT SURFACE AREAS: GEORGE H. CROCKER (1), JOSEPH F. MOON (2), JEFF A. NESSLER (2), AND SEAN C. NEWCOMER (2). 1. School of Kinesiology & Nutritional Science, California State University, Los Angeles, California; and 2. Department of Kinesiology, California State University, San Marcos, California.

2. The effect of the curvature of a swimming paddle on the propulsion force. Jessica Hargreaves, Barker College, 2022.

3. (Sidelnik and Young, 2006; Marinho, 2020; Vilas-Boas, 2015). Experiments In Fluids, 16 November 2021