By Steve Auchterlonie
The Pedal Stroke Part 1
It’s time for me to get bold, “Improving your pedal stroke efficiency will make you faster than buying the most aero and lightest bike and equipment, combined.”
Yeah, I just upset a bunch of bike shop owners. Let me be clear. Aero and lighter bikes and equipment do make you faster, no matter your level of cycling. Simply, I’m saying that time and effort invested in making you, the engine, stronger and more efficient has a greater effect for getting faster. Buying speed is relatively easy and pain free if the wallet and spouse are on board. Working on the engine is hard work…the hardest.
From personal experience, huge fitness and cycling strength gains are made in the first two years, then the dreaded plateau happens. It becomes very hard to improve significantly. Options available to break the plateau: coaches, power meters, weight room, weight loss, nutrition and buying speed through bike and equipment. I have tried them all, with minimum success. Frustration sets in. Time to find a new hobby? Then, I got lucky at the end of last summer…I learned that I may have the worst pedal stroke known to the sport. Lucky? I got excited about the potential improvement. The purpose of this article is to share what I’ve learned and prove my bold opening statement.
In my younger days, I played many sports…all required perfecting some skill critical to success in the sport: the swing in baseball and the curveball on the mound, the stroke in the jumpshot and swimming, the form in track hurdling and on and on. Why would cycling be the one exception to this? It’s not. Improving the pedal stroke is “old school” cycling. “Pedal circles”, “Scrape gum”, “unweight the backstroke”, single leg drills, rollers and fixed gear bikes are methods to focus on improving the pedal stroke. However, just like other sports, learning to pedal correctly is an elusive concept, apparently reserved for the “gifted.” This changed for me last summer. A new tool came to the market and I purchased one. This is the first on-bike tool that measures the efficiency of the pedal stroke. It shows what is wrong with one’s pedal stroke and shows how to improve. The purpose of this article is not to market that tool—the Pioneer Powermeter—but to share what it has taught me in the last nine months.
Some simple physics will help. What is power? Power is a physics concept to describe a force acting on a body which results in moving the body at some velocity, Power (P) = Force (F) x Velocity (V). In cycling, power can be measured at several points on the bike, including the rear hub, the crank system and the pedals. Historically, first generation power meters measured a cyclist’s total power generated to move the bike forward. The measured power was not directional—just total power. The newest generation of power meters (there is only one at this time) measures the direction of the power applied. Rather than just total power, this tool measures tangential power and radial power. What is that? Look at your crank arm on your bike (refer to figure below). Radial power is that directed parallel to the direction of the crank arm. Tangential power is that directed perpendicular to the crank arm. Try this test for yourself: pull as hard as you can straight out with the crank arm…what happened? Nothing. You did a lot of work (applied power) but the crank arm did not rotate…the bike did not move forward. Now, apply a finger of force to the side of the crank arm (tangentially)…the crank rotated and the bike moved forward.
Radial force is wasted energy; tangential force is 100 percent efficient in making the bike move. I thought the tool must be broken when I first purchased it last August. How could I only have 35-40% tangential power? I’m a better rider than that! Reality set in and my ego was sent out with the weekly trash. Data provided by the toolmaker documented that Cat 1/2’s are typically 50% efficient (tangential power/total power) and pros are 70+% efficient.
I am proud to say that I have raised my efficiency to 50% with a goal to get to 70%. It would take a book to share the journey I’ve traveled to achieve 50%. More importantly, I am much stronger/faster on the bike…ask those riding with me.
Here are the keys:
- The old school description for pedal stroke involved four zones: the downstroke (2-4 o’clock), bottom of stroke (5-7 o’clock), upstroke (8-10 o’clock) and top of stroke (11-1 o’clock). Conventionally, triathletes aim for an even power distribution throughout the stroke to save the legs for the run. Whereas bike racers should develop huge thrust through the downstroke because that is where 80% of the power is generated to go fast and accelerate. I’m a bike racer so I followed the huge thrust method. The huge thrust method produces the low efficiency value. I was confused! How could the pros be 70+% efficient with a huge downstroke thrust? They don’t pedal that way!
- I had to investigate so I invited several local racers to my lab and measured their pedal efficiency. Two notable subjects (both regarded as top level local racers who are excellent climbers) measured 70+% efficient. Their pedal strokes were much different. They described their pedal stroke as three zones: downstroke (1-3), bottom of stroke (3-9) and back/top stroke (9-1). They do not thrust the leg in the downstroke; instead, they just let the leg naturally extend. They emphasize pulling back and up from 3-9, and unweighting from 9-1. The resulting efficiency gain is amazing.
- We always refer to burning our matches in cycling. There are only a limited number of matches for each cyclist and they must choose when to use them. The more efficient pedal stroke “saves” those matches by not thrusting the downstroke until it is needed. The quads muscles are fresher for the key moments in the race!!
- Here is the greatest benefit for the efficient stroke, in my opinion. A higher efficiency pedal stroke requires significantly less effort/work/force to generate the same power. I could bury you with data I’ve gathered, but let me summarize for you:
- Rider A used 2800 Newtons (N) of force at 70 rpm to generate 300w of power, at 55% efficiency.
- Rider B used 2300 N at 70 rpm to generate 300w of power, at 72% efficiency.
- In my personal tests, I needed 2850 N at 70 rpm to generate 300w at 55%, but only needed 2250 N at 70 at 70%.
What does this mean? Force is how hard we push on the pedals. It is what eventually fatigues our muscles. At 70% efficient, I require over 20% less force to produce 300w than at 55% efficient. My legs are fresher for either a longer ride or for those critical moments in a race. I have saved matches.
Finally, time to prove my opening statement. At a 300w effort, a set of aero wheels saves maybe 15W, a aero frame another 15W, a time trial suit and helmet maybe 10-15W, totaling 40-45W of equipment speed: 40-45/300 = 13-15% improvement. For me, I have improved my efficiency 20% in nine months and plan to improve another 15-20% in the future.
Don’t just pedal harder…pedal more efficiently.
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