In response to a question frequently asked by our subscribers, our support specialist, Alex, recently posed a generalized version of this question as a topic for this week’s blog post. Simply, many indoor riders wonder if there is a relationship between cadence and FTP. So I think this is a good opportunity to provide a more useful & detailed response to the most common versions of this question which typically revolve around three more specific but equally important questions:
- Does your power output suffer or benefit from different cadences?
- Is there merit to training at certain cadences depending on the sort of events in which you participate or compete?
- Do certain types of intervals necessitate different cadences and/or gear ratios?
The Short Answer
First and foremost, a simple answer to the simple question, “Does FTP change with cadence?” My answer with one caveat is no, but I’m assuming riders gravitate toward a suitable cadence when they assess via 8-minute to 30-minute intervals. Most of us wouldn’t try to maintain our highest, sustainable power output turning the pedals 50rpm nor 130rpm, so I’m assuming that most riders will use a suitable cadence somewhere in the 80-100rpm range. And while these may not be optimal spins, they’re at least not gravely detrimental to your assessment. So barring a spin that falls outside of this reasonable cadence range, FTP will not change based on your spin alone.
Long Answer Preamble: Aerobic Fitness & Efficiency
The question of how a quicker or slower spin might translate to changes in power production and sustainability has been posed a number of times and is certainly worthy of a more fully developed response though, so let’s start with some basic muscle fiber physiology in hopes of elucidating why beginning riders gravitate toward lower cadences while more experienced (and often fitter) riders seem to have no trouble holding higher cadences for long periods of time.
Basically, it comes down to efficiency and aerobic fitness, or the lack thereof. As with anything, practice elevates efficiency, and in the case of riding a bike, we’re offered ample opportunity to practice the same movement over and over and over for, should we choose, hours on end. Done well, our efficiency trends only upward; done poorly, we still improve, just to a lesser extent, because our muscles really learn the movement and consequently decrease the level of muscle fiber recruitment leading to less stress on the body for the same amount of power to the pedals. And while I don’t want to downplay the endlessly fascinating capacity of our bodies’ adaptive capabilities, I do want to steer clear of a full-on science lesson. So suffice it to say, if you ride your bike with any measurable consistency, you’re going to become more efficient – just how much depends on your level of consistency and how well you practice safe & proper movement patterns.
As far as aerobic fitness, when you spin quickly the force output (i.e. how hard you push down on the pedals) is decreased and your slow-twitch, oxygen-dependent, high-endurance fibers – let’s call them endurance fibers – can shoulder the burden with little help from the more labor-intensive but low-endurance, fast-twitch fibers – we’ll call them power fibers (and for the sake of simplicity, we’ll ignore for now the intermediate fibers which blend attributes of both fiber types) – which require sugar/carbohydrate in order to perform work. With lower force requirements, you’re effectively asking less from the muscles but more from your heart & lungs, and the reason boils down to a matter of fuel preference.
Endurance fibers prefer the oh-so-plentiful and virtually unending fuel source, oxygen, while power fibers prefer the relatively-limited and not as easily replaced fuel source, sugar (glucose). Using the word “prefer” pretty inaccurately simplifies the muscle physiology of these 2 fiber types but will suffice for our purposes today. As riders become more aerobically fit, i.e. develop a more sufficient oxygen-reliant endurance base, spinning quickly (e.g. 95rpm) keeps the force output low thereby keeping the muscle stress and fuel consumption low as well since these endurance fibers are fully up to the task of repeating their oxygen-reliant contractions almost indefinitely. This sugar-sparing cycle perpetuates itself by encouraging riders to develop a quicker, lighter spin as a means to rider longer, farther, and eventually faster, all at a more limited expense to the muscles, i.e. less severe muscle fatigue.
Riders lacking this aerobic fitness, and more importantly (at least at the outset) lacking efficiency, misguidedly and probably unintentionally shift their riding stress onto the anaerobic system, the power fibers, by turning a bigger gear slowly. This leads to a shift in fuel preference, a shift toward sugar, because these power fibers can’t use oxygen, they can only use sugar. Add to this fuel shift the stress & actual damage brought on by these slower, more forceful, more taxing pedal revolutions and you have a recipe for fatigue. And that might simply mean you ride more slowly, you don’t ride as long or as far, or you hit the wall because you’ve diminished your sugar stores to the point of bonking, but in any case it means you aren’t making the best use of your muscular capabilities. Just think of how your muscles feel when you lift something really heavy 4 or 5 times but how much less exhausted they feel when you lift that same total load parsed into 10 equal parts.
The Long Answer: Cadence Effect on Power Output
All of this is somewhat of a preamble to the 3 questions I’ll now address, the first of which is, “Does your power output suffer or benefit from different cadences?” As always, it depends. Force intervals mandate slower spins because their goal (a questionable one at best) is to improve force production capabilities, to increase your ability to push the pedals harder, to recruit more muscle fibers. But how about VO2max or anaerobic repeats where you’re aiming to hold power well above FTP for short periods of time? Does a faster spin help you reach and sustain your goal output more effectively than a slower spin? Most definitely. When the power requirements are high, it’s nearly impossible to meet them with a slow, muscular spin – generating such high amounts of force would sap your muscles far too quickly not too mention how costly these high-force reps would be in terms of sugar usage. And how about your joints!? Your knees, hips, even your ankles, and all the connective tissue that supports them would take an unnecessarily brutal beating.
So we reduce this potential need for excessive amounts of force by spinning a little more quickly – reducing how hard we push the pedals while increasing how often we turn them – and thereby shift some of the stress from the muscles to the heart & lungs because now we’re more evenly splitting the reliance on particular fiber types and their associated fuel sources. That’s not to say that the endurance fibers are suddenly doing half the work; rather, we’re now delving into the intermediate fibers that can process both forms of fuel, sugar and oxygen.
So where should our balance between force and pedal speed be struck? As with so many performance-related questions, the answer depends.
The Long Answer: Event-Specific Cadence
The second question, “Is there merit to training at certain cadences depending on the sort of events in which you participate or compete?”, picks up where our last question left off.
Sooner or later, the specific demands of our sport must shape our training, but with a sport as multifaceted as ours this is a deceptively complex task with oftentimes outright complex solutions. Compare the demands faced by a Cat 3 criterium racer to those of an age-group Ironman triathlete to those of a young, aspiring BMX racer – dauntingly diverse, and this doesn’t even account for the levels of competition within each of these disciplines! And while there are some excellent tools that can help us determine ways to very specifically shape our training relative to highly specific cadence requirements, e.g. Coggan’s/Allen’s helpful if intimidating Quadrant Analysis, Bill Edward’s use of CompuTrainer’s CS application in tandem with his excellent Progressive Power Training approach; most of us have more general aspirations because we’re less concerned with being the best at one type of riding than being good at numerous types of riding.
Really simply, practice what you plan to employ. If you want to be able to routinely sprint out of corners and chase primes during criteriums, short, intense bursts of speed at high to very high cadences absolutely have to be a component of your training. If you want to sustain 75-85% of your FTP for hours on end while maintaining an aero position then it’s implied that you’ll have to log some extended sessions at subthreshold wattages employing spins that don’t overly tax your muscles yet keep your power on target all the while learning to effectively create power while scrunched into your time trial position.
So while early-season workouts may begin with a broad range of cadences and numerous general goals, they’ll inevitably morph into more specific workouts with increasingly specific goals and associated cadences.
The Long Answer: Intervals & Cadence
Which brings us to the final question regarding whether “… certain types of intervals necessitate different cadences and/or gear ratios?”. As I’ve already touched upon, certain workouts have specific demands that can only be met with specific cadences, and specific goals will shape your training and along with it, your cadence range. But what about those workouts you can perform equally as well at 80rpm as 100rpm? These are the more shapeable workouts which you can tailor more to your personal needs and limiters.
For instance, you’re a road racer who spends most of your Sweet Spot and Threshold workouts spinning somewhere between 80-85 rpm but who also recognizes a lack of acceleration when a breakaways leave you in the dust. Might be time to target an upward shift in your cadence range by performing these workouts in a slightly lower gear within the 85-90rpm range, and maybe eventually the 90-95 or 95-100rpm range.
Another example might be a half-Ironman triathlete who’s comfortable at 75rpm but has recognized the undesirable carryover between a slow cadence on the bike and a slow stride rate on the run. Might be time to target more speed work than in years past, try to lift that comfy spin as high as 85 or even 90rpm over the course of your base training by either increasing your wattage, or more likely, using 1 or 2 smaller gear combos. Whatever your case may be, there just aren’t too many riders who can’t benefit from a quicker, more relaxed (i.e. less forceful) cadence.
So while you may not be able to improve your FTP with a simple change in cadence, you can definitely improve your overall capabilities and move closer to accomplishing your goals by paying due attention to how quickly (relatively speaking) and how well you turn the pedals.
Until next time, train smart, ride hard, have fun.