Unlike frames, wheels, helmets, and hydration systems, triathlon apparel is rarely tested in the wind tunnel. Yet the potential for apparel to impact aerodynamics is just as great, as our recent preliminary testing indicates. The reason that testing apparel is so often disregarded is unclear to me. Is it because unlike their triathlon hardware colleagues, the textile manufacturers themselves never test nor tout the aerodynamic properties of their products? Is it because triathletes assume that anything without an airfoil is unworthy of consideration? Or could it be that self-appointed multi-sport pundits have simply neglected this section of the industry.
As one of those self-appointed pundits, I know I’m guilty. It’s not that I considered apparel irrelevant, it’s that I considered it aerodynamically insignificant. But then, two years ago, I was reviewing the results of an athlete who has done his own wind tunnel visit and had put an emphasis on apparel. I was surprised to see the significant difference in performance between his choices of apparel. I was determined to add it more rigorously to a future test.
And yet, when the time came to prioritize products in the tunnel, sure enough hydration and helmets took priority, while apparel became a secondary test “if we had time”. I regret that we did not have more time to test, because it ended up being the most eye-opening part of our preliminary tests. It seems that even when I was conscious of the neglect, apparel continues to be undervalued.
My goal going into these apparel tests was not to determine the “fastest” suit, but rather to get some idea of the delta between outfits. Would the performance difference between the best and worst be similar to what we see with hydration? Or would it be something akin to my theory about coming out of the aero position to drink: measurable, but inconsequential.
Additionally, with the growing popularity of compression gear when racing, as opposed to recovery, I wanted to get some idea of how wearing compression on the bike would impact aerodynamics. This is an interesting situation for half and full Ironman athletes, because many compression products recommend a maximum of a few hours of use during exercise, and therefore those longer-distance athletes would not wear the compression during the bike. For Olympic and Sprint distance, this would still be a relevant test.
I encourage the reader to review the Preliminary Wind Tunnel Results on Hydration Systems for disclaimers and clarification regarding baseline equipment, rider size and position, etc. as the apparel tests immediately followed our hydration tests during the same visit. Like that test, these apparel tests were done with 0 degrees of yaw, which makes them slightly more than interesting in terms of results. The reader may be disappointed in the limited number of products tested, due both to my limited vision plus the goal of simply determining the potential spread of apparel performance.
I’ll present this preliminary data in the same manner as the hydration results. Both in a 180k and 40k distance, with the 180k IM distance having the rider output at 150 watts, and the 40k Olympic distance at 225 watts.
Product |
40k in Time |
Seconds from 40k Baseline |
180k (112 mi) Time |
Seconds from 180k Baseline |
| Baseline De Soto Lift Foil | 1:07:46.80 | 0 | 5:56:31.80 | 0 |
| CEP Compression Calf Sleeve | 1:06:33.00 | -73.8 | 5:48:24.60 | -487.2 |
| 2XU Compression Calf Sleeve | 1:08:10.20 | 23.4 | 5:58:29.40 | 117.6 |
| Zoot 2-piece | 1:08:20.00 | 33.2 | 5:59:20.00 | 168.2 |
| De Soto 2-piece | 1:08:36.00 | 49.2 | 6:00:42.60 | 250.8 |
| Pearl Izumi PRO Suit | 1:08:39.00 | 52.2 | 6:00:59.40 | 267.6 |
| De Soto Forza Suit | 1:10:25.80 | 159 | 6:10:05.40 | 813.6 |
What can we learn from this initial wind tunnel run? Again, not much until we complete the additional yaw tests, but there are a few things that stand out:
- I always imagined that wind tunnel testing would bring peace and clarity to my life. Instead, it has done nothing but add anxiety. The difference between the best and least performing apparel is frightening. Gone are my innocent days of telling athletes that they can pick apparel purely based on price, carry capacity, comfort, and color. A difference of 13 minutes between 2 leading one-piece tri suits over an IM distance event is sending my adrenaline through the roof even as I write this. Ever wonder why your buddy always seems to come ahead of you on the bike, when you two have the same power to weight ratio? It’s these little unknowns. A seemingly inconsequential choice between name-brand tri suit A, B, and C can cost 13.5 minutes. My only consolation is that I have been racing with the Lift Foil for the last 4 years. Whew.
- The fact that some two piece apparel outperformed the tri suits is scary. Perhaps this is just repeating the paragraph above, but I would have thought that all one-piece would outperform all the two-piece.
- The compression gear result has to be the most interesting. Yes, the CEP compression improved aerodynamics, while the 2XU slightly decreased performance. All I can say is that I am looking forward to only shaving from knee to mid-thigh from now on, and let the compression gear cover the rest of my shave-scarred legs. Remember, CEP recommends that you not exercise for more than 2-3 hours at a time in their socks, so it just may not be a reasonable choice for half and full Ironman racing, but the possible time savings for CEP is quite tempting for the shorter distances. However, like the tri suits, not all compression appears to have the same aerodynamic result. It is just as possible that adding compression will slow you down as speed you up.
- How much is additional yaw testing going to make on apparel? I would imagine not nearly as much as hydration and helmets. Considering my theories have only been right 50% of them time when going into the wind tunnel, we’ll have to wait and see.
- Those of you who have been following the results of all 3 sets of tests (helmets, hydration, and now apparel) will note that it is an apparel item that has both the best performance (CEP Compression) and worst performance (De Soto Forza) of any other of the 36 products tested. Meaning, according to our initial tests, apparel may be the most important equipment choice you will make. When you think about it, this is really no surprise. What is going to expose to the most surface area? A water bottle, a helmet, or 50% of your body? It makes sense that apparel could be the most significant factor in your overall aerodynamics.
Overall, the apparel testing requires much more research, with both a broader range of product, and a broader range of yaw to complete the results. Until then, I’m keeping my Lift Foil and adding CEP compression to my Sprint and Oly racing, just in case.
You’ll recall my long argument against using aerodynamics as the primary factor in choosing a hydration system, and the same applies here. Sure, the Lift Foil looks good initially, but until the 2011 edition, it had no pad, and it still only comes in black. Can you imagine doing a full IM on a hot day in a black one-piece with no pad? For a Sprint-distance junkie like myself, this is no problem, but an IM athlete would have to consider comfort, temperature, price, and pockets as equally important elements in choosing a trisuit.
This report concludes our preliminary report on helmets, hydration, and apparel. I look forward to the next set of tests.
David, love the podcast and your articles. Was wondering if you could provide some insight into the margin of error one would expect in a wind tunnel test of this variety. Can’t recall ever seeing a mention of it in your analysis or anything similar in the tri mags. Not questioning your conclusions – I just don’t know and it’s an important bit of context.
I have to consider this VERY preliminary. It just doesn’t sound rational that the difference between two different brands of compression calf sleeves would result in a 1.5 minute advantage over 40K, and TEN MINUTES on an IM course.
While an interesting write-up, “Overall, the apparel testing requires much more research” is probably the key statement here.
Douglas nailed it. Preliminary, more research etc – there just needs to be more context than what is given, and this goes for any kind of performance evaluation study. Sure – you can compare different times and different equipment with each other, but there are too many factors, conditions, and variables to accurately quantify a meaningful result. Furthermore, the state of statistical studies in general provide very little use because of the issue with “context”. I digress.
While which fashion an athlete dons might be important to some, any up-and-coming athlete concerned with performance would be better suited worrying about fine-tuning their own “engine” through adequate training. That aspect of it alone will impact a race far more than the 0.014% performance gain they get from wearing one suit over another.
To say that it is “VERY preliminary” as though the information presented is useless is a little harsh. The tone and intent of the article was clearly to open up a topic of discussion and research and not to, at this moment, provide the reader with recommendations on gear or strategies. The fact that there was enough hard data presented to at least make a case that this is a topic worthy of further scientific research is VERY interesting.
Given the relationship between wind resistance and speed, these results could be very significant at the pointy end. If you were to move the average speed up close to 40km/hr for OD, there results will could be much greater.
David, thanks for the great podcasts and intersting topics. While listening to the last 3 with the results of the wind tunnel testing, a random question occured to me. We always hear about aerodynamics into the wind and different angles of yaw and all that. But has any testing been done that you know of about riding with a tail wind? For example does all the work that goes into making a bike more aero going into the wind decrease the amount of boost you get when the wind is coming from behind? With a tail wind, is it better to sit up and expose your back and get a little push? or is it still advantageous to stay in the aero position? Thanks for any insight you can provide.
Thanks for taking the time & expense to do all this testing.
Have you thought about doing a test with no shirt?
Very very interesting. Why should compression socks have such an impact? I think there is probably a masters thesis in there somewhere but as a preliminary guess. Compression socks are made of nylon and have small ridges, skin is smooth. Maybe the ridges are tripping the boundary layer giving a more attached flow around the calf (much like the dimples on a golf ball). Or, is it simply that it reduces the frontal area – I suspect it isn’t because humans are basically water and not very compressible so any reduction in the calf is just going to bulge out somewhere else.
Either the 2XU have a different pattern of threat that doesn’t trip the flow or the seam running down the sides, the point of maximum flow curvature is causing the flow to detach, stalling the calfofoil and adding drag….
David, I just got my weekly email from USAT and their discussion of Rule 5.11(f) made me think your your testing on the compression socks. Do you think there could be an interpretaion of the rule could have an impact on the use of compressionwear with such a dramatic difference as that which you tested? I know most people will think of compression accessories as clothing, but they are also not a “Standard” part of every Triathletes race kit. Would there be a possibility of some judge or committee somewhere saying they are extra equipment and therefore governed by this rule? Here’s the rule for your reference:
5.11(f)
No additional equipment, whether it is worn under the competitor’s clothing, over the competitors clothing, or is otherwise attached to the athlete’s body, which has the effect of reducing wind resistance is permitted. An exception is the use of safety helmets as described in Section 5.9. Such helmets may have the effect of reducing the wind resistance of the head only.
David,
This is all very interesting, but as a scientist, I have to say that the lack of replication makes these results very hard to interpret. There is always some variability in data… that there was such a difference between two brands of compression-wear and the weird pattern between the three front-end PD hydration systems makes me wonder if we’re not just looking at noise in the data.
I’m sure wind tunnel time is expensive, but if you repeated each run three times, then we could make actual conclusions and see where actual differences exist.
Any idea what is the combined time advantage between shaving or not shaving legs? (combined time gain from both swim and bike portions)
I like the idea of compression socks, but even with a wet suit on the drag swimming has got to be considerable. I can’t imagine much of a benefit if you have to take 30-40 seconds to get compression socks on your wet legs. Thoughts?
I have picked up on this conversation a bit late but had a clarifying comment. CEP ‘Sleeves’ are not recommended for more than 2-3 hours. Their ‘Socks’ however, are recommended for any and all durations. This 2-3 hours limit in sleeves may vary based on the individual’s efficiency of their venous return system. As there is no compression in the foot with a sleeve, an individual may experience swelling over long durations. A person with an ‘efficient’ venous return system may be able to wear sleeves longer without swelling in the foot. Alternatively, the socks have compression through the foot to aid venous return at rest, recovery or for longer duration activity. Overall, very interesting study!