Optimizing RPM
If you teach indoor cycling, you’ve probably led some type of cadence drill. Have you ever explored cadence beyond that? The cycling term used for pedaling speed, cadence refers to the number of crank revolutions per minute (rpm). While
cadence alone cannot reflect effort, it is
a critical variable that cyclists use to
manipulate intensity and efficiency. Small computers that monitor cadence have long been used by outdoor riders and are increasingly being offered by studio cycle manufacturers. Cadence meters often monitor additional variables, such as time and distance, but by far the most useful function for instructors and participants is the rpm feature. Understanding what this feedback means to the cyclist is the key to using a cadence meter effectively. And unless you’re a relatively experienced outdoor rider, chances are you have some questions, both about the numbers themselves and about how they can be useful to you and your students.
Outdoor riders have long appreciated the importance of cadence in cycling efficiency and performance, and in revealing individual strengths and weaknesses. Ideal cadence is generally learned through trial and error when riding outdoors. The rider sees how well the energy he is
expending helps him accomplish his goal of forward movement; and he observes others as well. His perception of his effort, in conjunction with his cadence and the gear he has selected, helps him judge what works best . . . and what doesn’t. Over time, by noticing which riding style moves him down the road fastest with the least effort, he learns which cadence seems the most efficient at a given power output.
Indoor riders do not have the advantage of seeing forward propulsion as the reward for their effort, making it harder for them to develop a “feel” for optimal cadence. However, even without the outdoor riding experience, you can teach your students this “feel” with the use of a cadence meter (see “Cadence Meter Drills” on page 83 for an alternate way to measure cadence). There is a good deal of research on cycling cadence and performance that we can draw from to
improve our teaching methods and to guide participants.
Optimal Cadence: Understanding
the Numbers
Optimal cadence can mean different things to different people, depending on the context. For example, cadence selections can hinge on the event itself, the terrain, particular goals (e.g., maximizing power output or efficiency; minimizing fatigue) and even comfort. Obviously, accelerating into a sprint will require a different leg speed than a multiple-hour endurance ride. Experienced outdoor cyclists spend the majority of their riding time at
cadences of 90–110 rpm. During the steepest of hill climbs, cadence may drop as low as 50–60 rpm, and elite-level sprinters may pedal at speeds up to 140–170 rpm. No single “magical” cadence is right for every cyclist, or in every condition.
Optimal cadence is also affected by experience and skill level. For example,
a newcomer to class may naturally prefer a cadence as low as 60 rpm, even at low workloads. While some instructors might urge this rider to “speed up,” research shows that the optimal cadence for a newcomer is apt to be considerably lower than for an experienced rider (Coast & Welch 1985). Many newcomers—and some regulars—get on the bike with little or no thought about the pedaling motion itself. People generally assume they know how to make a bike “go,” and they fail to recognize that efficient pedaling is a learned skill. Just like improving a golf swing or refining a swimming stroke, learning efficient pedaling style requires deliberate effort and many hours of practice. The goal, of course, is to develop the ability to deliver effective force to the pedals through as much of the stroke as possible, while minimizing energy lost from engaging muscle groups not directly
related to crank rotation. For the new or inexperienced rider, a cadence that is “too slow” may actually be beneficial, allowing more time for motor learning and patterning with each revolution. Riders will naturally self-select increases in cadence as skill improves.
An indoor cycle’s weighted flywheel, which generally weighs about 40 pounds, makes the cycle different from a regular bike. Once an indoor cycle is set in motion, this weight has a certain amount of inertia that makes pedaling at high cadences more attainable for a novice rider than would be possible on a road bike. Stephen S. Cheung, PhD, sports science and training editor at PezCycling News, says this inertia helps drive the legs through the “dead spots” of the pedal stroke and is not necessarily a bad thing. “After all,” he says, “the purpose of specific training is to overload your body by exposing it to a stress that it can’t normally attain—like a cadence of 130 rpm. This forces your body to adapt and train itself.”
It is precisely because of the direct drive and weighted flywheel that training leg speed on a studio cycle may be advantageous. However, instructors should recognize the difference in form and technique between a rider pedaling at 120–130 rpm who is bouncing and bobbling in the saddle and a skilled participant/cyclist who can maintain the same cadence with smoothness and control. The first rider should indeed be asked to slow down and regain control, but the second need not do so. Marsha Macro, studio owner, competitive cyclist and holder of national and world cycling titles and age-group records, finds that in her classes, “a cadence of 130 or more is usually out of control.” Take into account circumstances and individual differences before setting hard and fast “rules” on cadence limits.
Efficiency and
Optimal Cadence
Cycling science literature is full of studies on what is termed optimal cadence—the most efficient leg speed in a given situation. For any power output, there is a corresponding cadence that is the most efficient; in other words, that produces the greatest power output at the lowest energy cost. Older scientific studies have shown that at relatively low power outputs (wattages), there is a “U”-shaped
relationship between cadence and oxygen cost. In this model, oxygen cost is lowest at cadences of 50–75 rpm, which is far slower than what most road cyclists typically use. However, these studies had limitations: they were done at very low wattages, and the subjects were relatively untrained. Several recent studies that corrected for these variables revealed that, at higher levels of performance, 80–100 rpm proved to be the most efficient cadence. This explains and validates the use of such cadences by most experienced cyclists. These studies brought out a key point: at any given power output, there is an ideal pedaling cadence that grows linearly with the increase of force.
Is a Higher Cadence Better?
High-cadence cycling has been a hot topic since Lance Armstrong’s victories in the Tour de France with his high-rpm riding. His competitor, Jan Ullrich, stood in contrast with a bigger-gear, slower-cadence style. Researchers, coaches and cyclists took notice, creating a revolution in the prevailing thought about optimal cadence in cycling events like the time trial. Most cyclists would time-trial at 80–90 rpm, while Armstrong rode at a cadence of 110. The question on everyone’s mind: Should we all adopt the same high-rpm style?
At 60 rpm, it takes 1.0 seconds for the crank to make a complete revolution, while at 90 rpm, it takes only 0.66 seconds. Thus, the contraction time for involved muscles is 34% less at 90 rpm. Since the force of muscular contraction can limit blood flow and oxygen delivery to the muscle fibers, a shorter contraction time would be beneficial in delaying the onset of fatigue. A higher cadence would also require less pedal force. By decreasing both the amount of force and the length of time that force is applied per pedal stroke, a cyclist could potentially ride longer before fatiguing. This could save the muscles for subsequent efforts and faster recovery. But is a higher cadence better in shorter, more intense efforts like a time trial, or in a threshold-type interval in your indoor cycling class?
That question brings us back to Armstrong, and whether all cyclists should mimic his high-cadence style. Cheung cites the research showing that optimal cadence grows as power output rises. He believes that Armstrong’s unusual ability to generate power explains why his ideal cadence is higher than other cyclists. For those of us who are mere mortals, the same rules may not apply. In most cases, optimal cadence for higher-intensity efforts appears to be in the range of 80–100 rpm. The most important point for you to communicate to your students is that it is more important for them to be efficient (smooth) at their “normal” or self-selected cadence than it is to pedal as fast as they can just for the sake of a higher cadence. Cheung points out that “just spinning along at low wattages and high cadences is not necessarily going to make you fitter, or mean you’re a better cyclist. The name of the game is power output, not cadence alone.”
Variety Is the Key
One of the primary benefits of a cadence meter on a studio cycle is that from a training perspective, you know you are covering all your bases. It allows you as the instructor to structure your classes to include time at higher cadences (to develop smooth leg speed), lower cadences (to develop strength) and midrange cadences (to develop endurance and efficiency). Indoor riders have a tendency to unknowingly pedal at only one cadence, regardless of the drill or instruction. However, with a cadence meter, participants can see what they are really
doing; the numbers don’t lie! Macro and Cheung, as well as many other cyclists, like to use low-end cadences of 50–70 rpm to develop leg strength and high-end cadences of 120–140 rpm to develop leg speed. Macro adds that “high-load/low-cadence work must be done by driving the wheel with the leg muscles, not the knee joint.” Cheung further states that cadence is specific to the goal of the workout or drill, and he points out that “cadence needs to be planned, just as you need to plan the duration and intensity of the interval itself.” Variety in cadence allows for better training outcomes, taking riders outside of their comfort zones and working their weaknesses as well as their strengths!
Why Does Efficiency
Matter Indoors?
Why does efficiency matter in a noncompetitive, fitness-based program? After all, an inefficient riding style would translate to a greater caloric expenditure at any level of mechanical work produced. If a participant’s goal is to lose weight, wouldn’t inefficiency be a “good” thing? There are two reasons why the answer to this question is no. First, the most efficient style of riding is also the least biomechanically stressful and therefore the least likely to cause
injury. As a rider gains strength and fitness, and his ability to generate power increases, the force on the involved joints increases as well. Good technique minimizes joint stress. Therefore, it is paramount to emphasize an efficient riding style from the beginning. Second, cycling is not just an “exercise” but a skill-based sport, whether it’s taking place indoors or outdoors. Inevitably, your class participants will include recreational or competitive cyclists or triathletes looking for a time-efficient way to train. They will greatly appreciate an instructor who understands proper technique and can help them hone theirs.
Many indoor participants (who never thought of riding outside) have gained confidence and inspiration from taking classes; enough to take to the mountains or roads. If you teach sound skills, you help move riders toward a more enjoyable experience that may last a lifetime. Who knows? Maybe one of them will even
decide to pursue that yellow jersey!