Tag Archives: running efficiency

Why cadence matters.

A significant debate in the running world today concerns cadence. The question is: At which cadence should a person run? Some argue that the minimum cadence should be 180 steps per minute (spm), on the grounds that it is far more efficient than slower cadences.

Several important counterarguments have been made to this claim. One is that high cadences occur more often in elite runners, and then only during races (and that these same elite runners run at very low cadences during their warm-ups).

In this sense, nobody has ever run at one cadence—and indeed, there simply cannot be a “minimum” cadence: every run that anyone has ever run started out at a cadence of zero (when they were standing still) and their cadence slowly or quickly climbed to the cadence that they adopt habitually at a cruising speed. So, in “reality,” everyone has an infinite number of cadences at which they run: They start from a cold zero steps per minute, and pass through 0.0001 spm, 0.0002 spm, and so on, as they make their way past their habitual “cruise” cadence, up to their personal maximum.

The people who first prescribed a “running” cadence, when pressed on the issue of whether there is “one” running cadence, would almost certainly agree that people go through an infinite progression of cadences during either acceleration or warm-up. They would probably say that they didn’t mean that 180 spm was the sole cadence at which people should run (which is clearly impossible), but rather that 180 spm is the paradigmatic cadence of the human body—the cadence that these elite athletes warm up to (or should, if they don’t), in order to get the most out of their run.

(To be honest, I don’t know the rationale for 180 spm in particular as the cadence of choice—instead of say, 182 or 178 spm. I haven’t read anything about muscular dynamics that suggest that 180 spm is the optimum (or why it is). My belief is that the optimum would be somewhat dependent on the individual’s dimensions. I But it’s very clear that across individuals, 180 spm is a much more efficient cadence than 150 spm, for example.)

By this argument, why do high cadences show up the most in races? Because that’s when efficiency matters the most.

Think of this in the same way we describe “being awake.” We understand it to include a certain degree of alertness. We go through a spectrum of wakefulness from the point that we initially open our eyes and brush off the cobwebs to the point where we can be at the top of our game in a networking event.

It behooves us to define “full wakefulness” not at the point where we are not asleep, but rather, at the point where all the possible systems that contribute to alertness and cognitive function are up and running. If you can “get awake” but can’t brush off the cobwebs—implying that you can’t bring critical cognitive systems into play (or into play enough)—you’ve got a real problem.

Running works similarly. The main argument is that because these physiological systems create a higher degree of efficiency by producing a high cadence, it behooves us to understand “running” as including a high degree of activity of these physiological systems. (In these terms, “running-like movements” can occur at all cadences, but “running” occurs only at the full activation of these systems.)

Cadence increases efficiency because of its impact in a crucial neuromuscular process known as the Stretch-Shortening Cycle (SSC). When the foot lands, muscles all across the body are passively stretched. Then the muscles contract (or shorten) almost immediately, releasing the energy stored during stretching. This helps the leg recoil and be recycled into the next step.

The longer the interval between the initial stretching and the subsequent shortening, the more energy becomes dissipated in the form of heat. The longer the wait, the less mechanical energy available in the muscles and tendons at the moment of shortening.

At a low cadence, the interval between the stretch and the shortening is very long, meaning that a lot of energy is lost as heat (and efficiency drops). But as cadence increases, the interval shortens to the point that very little energy is lost (and efficiency rises).

I often write about how a new capability gives you twice the benefits you expect: For example, because of the improvement in efficiency that comes with a higher cadence, someone that runs a given distance more quickly is not only faster, but it takes them less energy to run the same distance. So the physiological improvements of proper training contribute to produce a much wider set of advantages.

The above shows yet more benefits: The energy that goes into stretching a muscle has to go somewhere: it can either get returned as elastic energy, or it can dissipate as heat. See the problem?

Even though I’m not aware of a lot of research on the conversion of elastic energy to heat, we can say this: the person with a longer stretch-shortening interval—who loses more stored mechanical energy as heat—has two problems, not one: As we discussed above, they have a lower energy return. But also, the additional heat creates a greater thermoregulatory load on the body.

So the runner with the faster cadence (usually the fitter and more skilled one) will not only be more efficient than the runner with the slower cadence, but they’ll also stay cooler. (And to top it all off, the fitter one is probably also the one with more developed cooling capabilities).

Just to be clear: if you’re fit and skillful, you’re also faster, more efficient, stay cooler and can cool down better, but if you’re less fit and unskilled, you’re also slower, less efficient, you get hotter and you’re not as good at getting rid of that heat.

Of course, none of this changes the fact that there is a curve that shows that people do in fact run at lower cadences at lower speeds, and at higher cadences at higher speeds. And it makes sense why they would: despite its benefits to efficiency, you don’t need a high cadence at a low speed. However, sticking to this descriptive reality of the world isn’t very helpful: the problem is that cadence has been shown to correlate more with absolute speed than with relative speed. This generally means that a relatively slow runner going close to their maximum speed will have a much slower cadence than a relatively fast runner going close to their maximum speed.

If we just go by the observed speed-cadence relationship (and let that iterate itself in every runner), the faster runner will always be more efficient. In other words, slower runners won’t get the chance to be efficient.

Good coaches try to get slower runners to run at a fast cadence to allow them to achieve a greater degree of efficiency (although the faster runner may have more overall efficiency due to other advantages). And by forgetting about speed (at least initially) and focusing on increasing cadence, it’s possible to accomplish exactly that.

Runners: Let’s not confuse Efficiency with Optimization

We should always be careful, as runners and athletes, when shopping around for new data to help us develop our craft. We should be even more careful when this data comes in a convincing format—scientific research—and alarm bells should go off when that research isn’t put in context.

Recently, I went to take the Pose Method Level 1 coaching certification, which I wrote a pretty popular review about. With this post, I want to begin diving a little deeper into the subject, starting by addressing one of the major scientific critiques towards the outcomes of minimalist running, forefoot striking, and the Pose Method: that these techniques are less efficient than heel-striking—namely, that they use more energy across the same distance.

Well, do they? Perhaps. Most likely, in fact.

However, seeking sheer reductions in energy use may be missing the point.

Let’s take a popular sport as an example: mountain biking. One of the first things you consider when buying a new mountain bike is whether you want dual suspension, or only on the front. This is a classic trade-off: the dual suspension lets you go on more rugged terrain, but it also means that less power from every stroke goes into driving the bike forward.

A dual-suspension bike is less efficient than a front suspension bike. That’s it, right? Front suspension bikes are superior. It’s a done deal.

Well, no.

Before I go on, let me be quite clear about the argument that I’m making. I’m not saying that less efficient options are better. I’m arguing that different options can’t—and shouldn’t—be judged on efficiency alone. I’ve seen it at least a few times in the running community: the studies on whether the Pose Method lowers running efficiency are presented in one stand-alone sentence, as if by itself, and without regard for the scope and depth of functions that the human body must fulfill, efficiency means something.

Efficiency alone means nothing. The questions we should ask is: what is it getting us, and what are we sacrificing by pursuing it?

Let’s go back to the mountain bike example.

Adding that rear suspension increases the capability of the bike to interact with more rugged terrain. If you land from a high jump with a dual suspension bike, you’re less likely to break the frame—or yourself.

Not a mountain bike, but I'd say that Danny MacAskill's legs count as suspension 1 and 2.
Not a mountain bike, but I’d say that Danny MacAskill’s legs count as suspension 1 and 2.

You’ll see this across all systems: increasing the dynamism of any system (which means both its capability to interact and its rate of interaction) increases its ability to interface with other complex systems (i.e. the environment). In order for this to happen, a dynamic system has to be working with sufficient moving parts, all of which take energy to function. If we just focus on cost-cutting measures—what gets me the least energy consumption, all else aside—we’re going to be undercutting that system’s optimization at some point.

That certainly seems to be the case in human locomotion, as suggested by this study (also cited above).

We’re making a very specific—and very generalizable—trade by adding a rear suspension to the mountain bike: we’re reducing its efficiency in order to optimize it to the environment.

Lowering the efficiency, however, does not immediately mean that you’re optimizing something. In fact, it’s typical to find that if optimization drops below a certain threshold, so does efficiency. A bike needs intact tires to function well. You can’t be riding on the rims during a race and expect to be very efficient.

Optimization, although more costly in the immediate term, is more cost-effective than hard-edged efficiency over the long-term. What happens if the bike frame breaks? The amount of power that goes from your downstroke and into the ground drops to zero.

We all live in this compromise: we want to increase our efficiency, but not at the cost of optimization. Let’s use a gait example. Is it more efficient to shut off your gluteus maximus, hamstrings and quads while running? Probably—those muscles are huge. They’re consuming lots of sugar and oxygen in order to stabilize the pelvis and move it over the femur and the knee joint.

In addition, they’re mostly only active from contact to midstance. They’re the biggest muscles in the body, and they don’t even help you push off. Less efficient? Sure! Why not just let momentum carry your GCM—general center of mass—over your knee joint while keeping the hip extensors quiet?

Because your femur would summarily come off your tibia, and your patella would pop off and land somewhere on the ground in front of you. Once again, the efficiency of your gait would drop to zero.

I’m not making an argument for any particular method or stride type. (I believe those arguments are there to be made, once we have satisfactorily defined what we mean by “stride type,” but not in this post). The takeaway, as I mentioned above, is that in order to optimize something to the environment—say, in order to allow our body to remain in a configuration which can adapt its footfalls to variable terrain—we’re going to be sacrificing some raw efficiency.

Is forefoot-striking or Pose the best way to optimize the body? Well, that’s a different question.

UPDATE: In this article, “Pose” refers to excellent pose technique. (This was brought up by a concerned reader on a Facebook thread.) Indeed, all running and all movement is an alternation of poses (think about the kata in martial arts). For better or worse, the question remains in the scientific and running communities: is excellent Pose technique the best way to run? Many try to detract from it by saying that it is less efficient. I believe that regardless of whether it is or not, that line of argument largely misses the point.