What Makes You Faster: Shaved Legs Or Optimal Fuelling?

As athletes, we are bombarded with different methods to enhance our performance. From aero socks, deep section wheels, and waxed chains to the latest dietary supplement and training techniques, there is no shortage of ways we can spend our money in the name of performance.
 

When trying to navigate the often complex topic of performance, it’s a challenge to quantify what the actual performance benefit of each of these tools in the toolbox, so to speak, adds up to.
 

Shaving legs is engrained in cycling culture, with reasons for doing it ranging from making gravel rash easier to clean, aiding massage, to just feeling nice, to the out and out performance enhancement through aerodynamic gains. But, how does the aerodynamic improvement compare to other strategies and is it really worth the effort?

As nutritionists, we’re not up to speed on the latest aerodynamic research (nor do we really understand it!). However, the cycling media features several publicised tests of athletes comparing shaved legs to hairy legs, and the results have often been pretty surprising.

Lionel Sanders (Pro Triathlete) - 13 Watts Faster at 250Watts - https://www.youtube.com/watch?v=5M3Z0ClhNsU

Specialized Bikes Aero Testing - 70seconds faster over 40km (although they didn’t specify how long 40km takes) - https://www.youtube.com/watch?v=DZnrE17Jg3I

 Global Triathlon Network 5.58Watts at 30km/h and 17.56Watts at 40km/hr - https://www.tiktok.com/@globaltriathlonnetwork/video/7241574147808087322

As with many areas of cycling and science, there is always complexity. The results will only be relevant to the specific situation (and potentially the individual rider) in which the test occurred. They can be affected by a few different factors, from the speed the rider is riding at (as clearly demonstrated in the GTN Video) to the change in the surface as a result of shaving, but these figures give us something by way of reference for comparison.

So, how do these performance improvements compare to a fundamental nutrition strategy like fuelling (i.e. eating carbohydrates around the session)? 

Let's take the example of one of the early studies evaluating the impact of multiple transportable carbohydrates on cycling time trial performance. In this study, they took 8 riders and put them through three different trials. They consumed either a water placebo, a glucose or a glucose and fructose drink providing 108 grams of carbohydrate per hour during two hours of fixed-intensity cycling, before participants then performed a one-hour time simulated trial as fast as possible.

As you can see in the graph below, the results were pretty mind-blowing. In the placebo trial, participants averaged 231 watts, with participants producing an average of 275 watts over the hour in the glucose: fructose trial—an increase in power of nearly 45 watts! This is equivalent to a 19% increase in power output, providing performance gains many fold higher than that of shaving legs.

However, comparing a single study like this can be problematic, particularly if it cherry-picks the best data, so let’s look at the bigger picture. In 2014, two researchers published a systematic review of the effects of carbohydrate supplementation on different exercise durations. They reviewed the results of 50 previous studies (giving us a much better idea of the bigger picture), of which 82% showed a statistically significant improvement in exercise performance as a result of carbohydrate supplementation.

One key conclusion was that there was a significant correlation between exercise time and the effect of carbohydrates on performance vs. placebo. As we can see on the graph below from the study, the longer the exercise task, the greater the percentage improvement in performance. Generally every exercise task over 1 hour in duration is likely to see in the region of a 5-10% improvement in performance as a result of taking in carbohydrate compared to a placebo.

 This effect of time is because one of the main mechanisms through which carbohydrates aid performance is by providing additional fuel. This helps maintain rates of carbohydrate use, prevent a drop in blood glucose, and stave off fatigue, particularly when fuel availability is limited. If a rider already has enough glycogen to get them through the exercise tasks, additional carbohydrates will have a relatively limited impact compared to if the exercise task is likely to deplete glycogen stores, hence the smaller performance improvements in short duration time trials.

For shorter exercise tasks, carbohydrates can still help, but the effect is likely to be due to carbohydrates stimulating reward centres within the brain, which help make exercise feel easier and, therefore, enhance performance rather than simply providing more fuel (which isn’t a limiting factor).

So, in effect, while leg shaving may certainly provide some performance benefit, under circumstances where the rider speed is sufficient and aerodynamics is likely to play a role in supporting performance, the impact of fuelling on performance, particularly in longer exercise tasks, is likely many fold greater, and as such, fuelling as a performance-enhancing strategy certainly deserves the attention of riders searching for performance and should be close towards the top of the list when it comes to looking for way to enhance performance. 

To learn more about how to optimally fuel your training and racing, do check out fuel the rider academy.

Coach Ben