The Science Behind Going Slow to Be Fast

The concepts of central and peripheral conditioning help explain why an effective training base period leads to speed and durability in the race season.

Pathways Logo Cycling Base Training Pathway - Fast Talk Laboratories graphic interpreting polarized training method as 80/20 mix of intensities, from green to yellow/red
Photo credit: Kenny Withrow

“This is going to hurt…” 

It was November. I was an overweight newly upgraded Cat. 2 rider on my first session at the Canadian National Cycling Center. About 20 riders had shown up. Half were guys like me—unknowns. The other half were national champions and Olympians—guys I had dreamed of riding with. Right now, though, all I could think was, “What have I gotten myself into?” 

For the first hour I didn’t even reach for my bottle for fear of getting dropped. We hit the first climb and, just like that, several riders did just that. Poof, gone. Some of the other champions and famous folks started slipping out the back.  

I was shocked, but I felt I had to prove myself. I was about to attack when Erinne Willock, an Olympian, and still the smartest cyclist I’ve ever met in terms of her training, stopped me. In the nicest way possible she told me, “Don’t be an idiot.”  

I listened; I slowed down. For months after that day, I allowed myself to get dropped. Then, in February, something changed. The unknown riders who had been attacking in November were suffering, and the big name riders started winning the climbs. And, best of all, I was going with them.  

I had gotten fast by going slow. 

It’s all about that base 

We’ve all heard it: go slow in the base season. And we’ve all questioned it. Going slow might make you strong but shouldn’t going fast make you that much stronger? If I start my hard intervals in November, won’t that give me a leg up? Allow me to try to convince you otherwise, and help you get fast the slowest way possible. 

Let’s start by looking at VO2max. It’s a measure of the body’s ability to take up and use oxygen—an important measure in an aerobic sport like cycling. VO2max is actually a bad predictor of performance, but it’s a great tool for looking at training.  

For decades, scientists have researched which factors are most important in determining VO2max, and it’s still a hot debate whether “central” or “peripheral” factors are most important. Central conditioning refers to the heart’s ability to deliver blood to working muscles. Peripheral conditioning, on the other hand, builds the muscle cells’ ability to take up and use that oxygen.  

Central conditioning 

The concept of central conditioning accounts for up to 80% of the improvements in a trained cyclist. It’s what we’re focused on in the base season. Two things affect your heart’s ability to deliver blood: how fast it can beat and how much blood it can pump per beat (called stroke volume.)  

Sadly, our max heart rate is genetically set and it only gets lower with age. We can’t train it. Stroke volume, on the other hand, can be trained. When we talk about improving central conditioning, we’re talking about stroke volume.  

Thus, the question becomes, how do you train stroke volume? To train a system you must hit it hard. Fortunately, stroke volume has a low ceiling—it peaks at about 60-65% of your maximum heart rate. In other words, if you’re killing yourself at 190 beats per minute (bpm) up a climb, your maximum stroke volume topped out at 123bpm. Going harder may feel good, but it doesn’t add any gains to your central conditioning.  

Training stroke volume increases the size of the heart’s left ventricle. Because it’s a structural change, it takes time to come about. Therefore, the key isn’t about going hard, but about doing this training often and for a significant length of time. It takes months to see gains in a single season and up to 10 years to reach your personal potential. 

Peripheral conditioning happens fast 

Your working muscles’ ability to use oxygen is affected by two things. The first is the capillary density of your muscles. This structural change is trained like stroke volume; from a training perspective, think of it as part of central conditioning.  

The other is the mitochondrial density of your cells. As the powerhouses of your cells, mitochondria use oxygen to produce energy. For cyclists, mitochondria are a powerful component of our physiological engine. To improve your peripheral conditioning, you must go hard. However, unlike central conditioning that takes years to develop, it takes only six weeks to fully develop mitochondrial density. 

Sounds great, right? You might be thinking: Why not do it as soon as possible? Well, unless you just bought your first bike, most of your peripheral improvements are in your fast-twitch fibers. Forcing them to work aerobically is what allows you to set personal bests on that 10-minute climb. But it also makes your fast-twitch fibers cranky. They don’t like working aerobically.  

It takes just one week of detraining for fast-twitch muscle fibers to lose 50% of their mitochondrial density. Once you start building your peripheral fitness, you have to keep working it, or you lose it (which would mean doing several high intensity rides per week).  

The catch is that fast-twitch fibers won’t remain aerobic indefinitely. Eventually, you will be forced to let them detrain; often this takes the form of burnout. Building your peripheral conditioning in November is a great way to be the fastest rider in the February group ride—and be cooked by April. 

Muscle fiber mitochondrial content

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