What Is Training Load in Cycling and How Is It Calculated

James. Welcome to the WattPlan Podcast. I'm James. Between the family, the work, building WattPlan and chasing the occasional podium, I've read more about training stress than any sane person should. This week, the number that turns up under every single ride. What is Load actually measuring, and how much of it should I be piling up? Lyra is our AI research voice, and every study she brings up is linked in the show notes.

Lyra. Load is one number for how hard a ride was for you, not for anyone else. It multiplies how long you rode by how hard you rode relative to your FTP, and it's scaled so an hour at FTP scores 100. So a short hard ride and a long easy one can land on the same number by different routes.

James. Relative to my FTP. So the same ride scores differently for me and my mate?

Lyra. Exactly. Two hundred watts for an hour is threshold for one rider and a cruise for another. Load asks what the ride cost you, which is why it needs your own FTP to mean anything.

James. Go on then, what's the actual sum?

Lyra. Hours, times Intensity squared, times a hundred. Intensity is your Weighted Power divided by your FTP. Weighted Power counts surges more heavily than a plain average, because a ride full of attacks costs more than a steady one with the same average.

James. Squared? That sounds like it punishes hard riding.

Lyra. It does, on purpose. An easy hour at an Intensity of 0.7 scores about 49. Ride that same hour at FTP and it's 100. So roughly twice the Load for less than half as much power again. Hard efforts cost you disproportionately more, and the squaring is trying to capture that.

James. Give me an everyday one. A normal Sunday ride.

Lyra. A two hour endurance ride usually lands somewhere between about 80 and 120, depending on how steady you keep it and how many hills you find.

James. And an hour of intervals?

Lyra. Usually less than people expect. An hour of sweet spot in the plan often comes out around 55 to 70, because the warm up and the recoveries between blocks are easy. So two hours of steady riding can outscore a session that left you lying on the floor.

James. That feels wrong, though. Surely the session that wrecked me counts for more?

Lyra. You've found one of Load's honest limits. A hundred from easy riding and a hundred from threshold intervals score the same, and they don't feel the same or train the same thing. Load measures how much stress, not what kind. It's a quantity, not a recipe.

James. What if there's no power meter? Half my winter rides are on the old bike.

Lyra. Then WattPlan works Load out from heart rate, against your maximum, resting and threshold heart rates if you've given all three, or your maximum alone if not. It's less precise, because heart rate lags and drifts. With no sensor at all, your answer to how hard the ride felt gives it its Load. A planned session that felt as it should keeps its planned Load, and an unplanned hour that felt hard comes out at about 70.

James. Okay. So that's one ride. What happens to the number after that?

Lyra. It feeds three lines. Fitness is a 42 day weighted average of your daily Load, Fatigue is the same over seven days, and Form is the gap between them. Which is where the first of the two studies we looked at comes in.

James. Go on.

Lyra. It's a 1990 paper in the Journal of Applied Physiology by Morton, Fitz-Clarke and Banister. In their model, every dose of training produces two responses at once, fitness and fatigue. Without training, both fade away exponentially. Put the two together and you can predict how someone will perform. [2]

James. Two responses from the same ride. And that actually worked on real people?

Lyra. The predictions tracked measured performance through training and through a taper, in trained and untrained people alike. It's the idea underneath the Fitness chart. The same session makes you fitter and more tired, and the tiredness fades faster.

James. Right, so how much should I do a week? Because there's always the ten percent rule. Never add more than ten percent a week. That's gospel, isn't it?

Lyra. It's repeated like gospel. It's barely been tested. The best test we found is the second study, a randomised trial in The American Journal of Sports Medicine with 532 novice runners training for a short recreational race. One group built up gradually on the ten percent rule over a longer programme. The other followed a standard, quicker one. [1]

James. And the careful group got fewer injuries.

Lyra. They didn't. About one in five runners in each group was injured, and the difference between the groups was essentially nothing. Following the ten percent rule on its own didn't protect them.

James. Runners, though. Nobody's shins fall off on a bike.

Lyra. Fair, and it's a real limit. They were novice runners, and the outcome was injury, not fitness. What it does tell us is that one tidy percentage isn't the whole story. How fast you can build depends on where you're starting, how many hours you have and how well you recover.

James. So how does WattPlan decide how much to give me?

Lyra. From your Fitness and your hours. You choose how quickly you'd like Fitness to climb each week, the plan builds the weekly Load to match, and it tells you plainly when your hours are what's holding it back.

James. Is there a number for a single ride where I know I'll be cooked tomorrow?

Lyra. As a rough guide, under about 150 most riders are recovered by the next day. Go well beyond that and expect heavy legs the day after, and the really big days take several. That's why a good week puts an easy day or a rest day after a hard one, so Load arrives in waves rather than a wall.

James. Someone new to structured training is going to hear Intensity squared and run a mile.

Lyra. Then they can skip the sum. If you're new to this, ride the plan, say honestly how hard each ride felt, and the Load takes care of itself. The number only starts earning its keep once you've a few weeks of it to compare.

James. And if you train with power?

Lyra. Keep your FTP honest. Every ride is scored against the FTP you had when it came in, so an FTP set too high makes every ride look easier than it was, and one set too low inflates everything. And if a power meter drops out halfway round, correct that ride's Load by hand. A Load you type in stays as you typed it.

James. And if you race, where one Saturday chain gang can blow the whole week?

Lyra. If you race, those are exactly the days Load is for. A hard group ride or a race counts in full, and a long, hard one can score a few hundred. Tell WattPlan about a hard club ride you always do, and the plan counts it as one of the week's hard days rather than adding a session on top.

James. What doesn't Load see?

Lyra. Plenty. Work stress, a bad night's sleep, a cold coming on. None of that is in the number, and all of it changes how a ride lands. It assumes your FTP is right, and it can't tell you whether the training is turning into fitness. Chasing a bigger number is how people end up grinding out grey zone miles that cost a lot and buy very little.

James. Right, what should I actually do with this?

Lyra. Three things. One, open You, then Metrics, and check your FTP and heart-rate numbers are current. Two, open three of last week's rides and see where each Load came from, power, heart rate or how it felt. Three, after your next hard session, rate how hard it was honestly, because the Coach reads that alongside the numbers.

James. So the number's only as honest as my FTP and my answers, and a big one isn't automatically a good one.

Lyra. Think of Load as the receipt, not the score. Spend it where it buys you something, and leave enough in the bank to recover.

Lyra. The full article and every study we mentioned are on the WattPlan blog, linked in the show notes. And if you've enjoyed this, follow the WattPlan Podcast wherever you're listening, so you don't miss the next one.

James. And if you want a plan built around the time you've actually got, get WattPlan on the App Store or Google Play. Thanks for listening.

Voices produced with ElevenLabs. James's voice is a clone of his own, Lyra is an AI voice, and James reviews every episode.