You’ve developed strength in the weight room, you’re interval training, and you’re fired up to compete in the local time trial or triathlon. Your power is good but you’re worried if your aero position is as sleek as it could be. You’ve seen the pros’ aero position (photo) on their TT bike and want to look like them — a cruising landshark, cutting through the wind.
How can you achieve the most aerodynamic position so you slice through the air, thus going faster for the power you’re producing?
Testing in a wind tunnel is the time-honored way to get aero. But it’s also expensive, making tunnel time fine for sponsored pros but prohibitive for the rest of us. Even the mobile wind tunnels available today aren’t exactly cheap. Let’s look at a more doable way to decrease your frontal area — the shape the wind “sees” as you ride.
5% Sleeker = 60 Seconds Saved
Jim Martin, Ph.D., has discussed a study that showed how decreases in frontal area of 5-20% affected times over a 40K (24.8-mile) time trial. He used a combined rider/bike weight of 80kg (176 pounds) and an average power output of 300 watts. A mere 5% decrease in frontal area translated to nearly a minute saved over 40K. An aero improvement of 15% was good for almost 3 minutes. Roughly a minute was saved for each 5% less frontal area.
According to Martin, you don’t need a sophisticated and expensive wind tunnel to achieve a low frontal area. You can do it with the help of a mirror and a friend to observe you while you pedal on a trainer.
The goal is to get your torso horizontal to the ground. Lower the handlebar and forearm pads until that position is achieved.
Remember to slide the saddle forward several centimeters to open the angle between your upper thighs and chest. The exact amount of forward movement isn’t crucial, according to a study done by researcher Dan Heil Ph.D. of Montana State University. He showed that hip angle can change 10 degrees on either side of the “optimum” angle before there’s a significant decrease in oxygen uptake.
Head Down, Eyes Up
Viewed from the side, your head should be lower than your back. If your friend looks at you from the front and can read what’s written on your jersey, you’re not low enough. Elbows should be as narrow as possible without compromising breathing and bike control.
This flat-back position shouldn’t hinder your vision. Even though your head is lower than your back, Martin says you’ll be able to see down the road by rolling your eyes up.
One way to check your position is to look at pictures of top riders like the one above. “If you look like these riders,” says Martin, “you’ll have [minimal] drag like these riders.”
What if this low, flat position robs power? After all, it’s difficult to pedal at maximum strength with your back horizontal.
Martin points out that endurance power (like in a 40K time trial) is only 25-30% of maximum power, such as you’d generate in a sprint. For example, you might hold 1,000 watts for a 5-second sprint but time trial for an hour at an average of only 260 watts. The sprint requires all the musculature and effort you can muster — out of the saddle, snorting and grunting. You couldn’t do it in an aero position. But you can generate 260 watts for a much longer time even in a very low posture.
That said, most riders do sacrifice a little power when they adopt a sleek TT position. But due to their much improved frontal area, they go faster. The trick is to find the best balance between a low position and power production. It results from continued experimentation and competitive experience.
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