How much performance boost are you getting from a wetsuit?

As many of us are aware, the swimming legs of most long-distance triathlons
are wetsuit legal, allowing athletes to don non-porous suits for the opening swim. Ostensibly, athletes wear these suits to stay warm in cooler water (generally less than 78 degrees Fahrenheit), but are generally worn for another reason: the increased volume, minimal additional mass, and streamlined characteristics of a wetsuit results in improved hydrodynamics, allowing athletes to move through the water both more rapidly and with greater ease. In this recent publication, a Japanese group set out to quantify the effect of wearing a wetsuit on individual athletes during two 5-minute swim trials at 60 and 80% of each athletes maximum oxygen absorbtion rate (previously determined). Here are their findings: On average, wetsuit wearers moved 5.4% faster than those wearing a speedo-style swimsuit, and experienced a 14.4 and 7.5% reduction in energy costs to acheive these results (at 60 and 80% respectively). The researchers also measured stroke length and stroke rate of the participants, and found that, while stroke lengths were similar, stroke rates were slightly higher in individuals wearing a wetsuit. The results of these findings suggest an inherent advantage in wearing a wetsuit during the swim. But that's not all. According to this study there is a significant difference in cycling power output (a whopping 12%) after a swim preceded by a swim in either a speedo or a full wetsuit. So... yet another reason to wear the wetsuit. If you don't have the funds to buy a fancy new wetsuit, there's always the poor man's option: drafting. As in cycling, there is a small efficiency gain when swimming behind someone else in their slipstream. This study measured that difference on a bike test preceded by either a drafting or non-drafting swim, and found that one typically produces 4.8% more power after drafting during the preceding 750 meter swim. And since I've never heard of a race that penalties you for drafting, I'd say go for it, even if you're wearing a wetsuit too!