Rider questions
A question a rider has actually felt on the bike, answered with physiology: the answer first, then the mechanism, then the experiment that shows it. Each one is also a short video.
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Made with Bryn Griffith
Why do my easy rides have to feel so easy?
Because the goal isn’t to get the most out of today’s ride. It’s to get the most out of your whole season, and easy riding trains you at a price you can keep paying.
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What do mitochondria actually do when I ride?
They run an electrical machine. They take the electrons out of your food and let them fall to the oxygen you breathe, and the fall charges a membrane, which drives a tiny motor that makes ATP, the energy currency your muscles spend. And training mostly changes how much of that machine you have, not how much it gets out of each breath.
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Why can I surge above threshold and still recover?
Because above your threshold, you’re spending from a limited reserve of extra work, and a short surge spends only part of it. Drop back below it, and the reserve refills: gradually, and faster the further below you go.
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Why am I gasping before my legs give out?
Usually, it isn’t your lungs failing. An effort that hard demands enormous amounts of air, and moving it is work in its own right: near your maximum, your breathing muscles claim a share of the blood your heart pumps, partly at your legs’ expense. So breathing that hard is one of the things tiring your legs.
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Does keto or fat adaptation make me faster?
So far, not reliably. It does make your body burn far more fat. But in elite race walkers, 3 weeks of hard training on keto didn’t make them any faster in a race, and in one study of cyclists, 6 days of high-fat eating, even with a day of carbohydrate loading after it, left their one-kilometre sprints weaker.
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Is a sprint really anaerobic?
Less than the name says. Your aerobic engine works through every all-out effort, and the longer the effort, the bigger its share of the bill: very little over a few seconds, but by 30 seconds, about a quarter of the energy.
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Am I burning fat in zone 2?
Yes. If zone 2 means easy riding below your first threshold, its upper part is usually close to where fat burning peaks. But you aren’t riding on fat. Even at its peak in a lab test, fat on its own pays for something like 100 W for a typical athlete, and less on a bike. So carbohydrate is paying a big part of the bill all ride, zone 2 included, even on an empty stomach.
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Can I raise my VO2max, and does it even matter?
Yes, but after the quick first gains, slowly. On a bike, your VO2max, the most oxygen your body can use flat out, is set mostly by how much blood your heart can pump, and a bigger pump takes seasons to build. And it matters less than the number suggests, because riders with the same VO2max can ride very differently.
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Why is my fifth attack weaker than my first?
Largely because the reserve that pays for the first seconds of an attack refills on oxygen, and a full refill takes minutes. When attacks come close together, it doesn’t get those minutes, so each attack after the first starts with the reserve only partly refilled.
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60, 90 or 120 g of carbs an hour: how much do I actually need?
Those numbers mostly reflect how fast your body can take in and use a drink, not how much carbohydrate your legs are burning. What you burn rises with your watts, so the harder you ride, the more your own carbohydrate has to cover. And in a study that tested it, drinking more didn’t measurably lower how much of their own the riders burned.
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Is zone 2 a waste of time?
No, but probably not for the reason you’ve heard. Session for session, intervals add about as much to the mitochondria in your legs as a steady ride does, in fewer hours. The case for zone 2 is that it’s hours you can recover from, so you can stack far more of them, and what you’re really training is the season, not the session.
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Why do I bonk?
It feels like a switch, but it’s been building for hours. The carbohydrate in your legs runs down from the first hour, the sugar in your blood quietly covers for it, and when that runs short too, the watts you’ve been holding cost more than you can pay.
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What workouts improve lactate clearance?
There’s no special one. Steady riding and intervals both build your aerobic engine, and that one engine decides both how much lactate you make and how much you clear. In one detailed experiment, making less was the bigger part.
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Why do I lose fitness so fast when I take time off?
Part of what goes first isn’t muscle. It’s blood plasma, the liquid part of your blood. Training expands it within days, and when you stop, it’s quick to drain away.
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Why do I fall apart in the last hour of a long ride?
Because the power you can sustain isn’t fixed. After a couple of hours of hard riding it can drop, and the same watts start costing more. How well you resist that has a name: durability.
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Why can’t I hold intervals just above my FTP?
Because FTP is an estimate of your threshold, not a measurement of it. It can land above your real limit, and a few percent past that limit, your body can no longer settle.
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Why does my heart rate keep rising on long rides at the same power?
The short answer is that it’s mostly your temperature, not your legs. The longer answer is a neat piece of physiology, with one experiment that shows how it works.
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What is zone 2, really? Why do my apps disagree?
Because zone 2 means different things in different zone systems. In most of them, it’s easy endurance riding. In the three-zone system behind polarized training, it’s the harder middle ground, the zone polarized training tells you to keep to a minimum.
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Why do my legs burn on hard efforts, and is it lactic acid?
Not on its own. The burn is a set of sensors in your muscle reading a mix of chemicals that rises as the work gets harder. It’s a gauge, not damage.
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