The century is the bucket-list ride. A hundred miles, the round number that means you've done something real on a bike. And every year, thousands of riders turn up to one underprepared — not because they didn't train, but because they trained for the wrong thing. They chased the distance and ignored the demand.
Here's what nobody tells you about the hundred-mile ride: finishing it strong has very little to do with how long your longest ride was, and almost everything to do with whether the fitness underneath you can absorb the cost of the day. And the language for understanding that cost is TSS — Training Stress Score — which TrainingPeaks has been quietly putting on every one of your rides this whole time.
What a century actually costs
Let's put a number on it. TSS is built so that one hour ridden flat out at your threshold — an intensity factor of 1.0 — scores 100 points. Everything else scales from there, and for a steady sustained ride there's a clean way to estimate it: take your duration in hours, multiply by the square of your intensity factor, and multiply by 100.
So a century that takes you five and a half hours at an intensity factor of 0.68 — a sensible endurance pace — works out at roughly 5.5 × 0.46 × 100, which is about 255 TSS. Push that to a six-hour ride at 0.70 and you're near 295. Ride it hard, hilly, at 0.78 for six hours, and you're up around 365. Add real climbing and a competitive group and 400-plus is on the table.
So the honest range for a century is about 250 to 350 TSS for most riders riding sensibly, climbing toward 400 if it's hard or hilly. That's the size of the bill the day is going to hand you. The whole question of preparation is whether your body can pay it without going bankrupt at mile 70.
Why CTL matters more than your long ride
This is the part that catches people out, so it's worth slowing down on.
Most century plans are built around the long ride. Get your Sunday ride up to 70 miles, then 80, then 90, and you'll be fine on the day. There's some truth in it, but it misses the real driver, which is your Chronic Training Load — your CTL, the rolling 42-day average of your training stress that TrainingPeaks plots as your fitness line.
Think of CTL as the size of the workload your body is used to handling. If your CTL is sitting at 40, your body is accustomed to a certain weekly and daily load. Now you hand it a single 320-TSS day. That ride is something like eight times your average daily stress. Your body has no frame of reference for it. You'll get round, maybe, but you'll be wrecked for a week, and you'll spend the back half of the ride in survival mode.
Now picture the same century with a CTL of 75. The day is still hard — 320 TSS is always hard — but it's a familiar kind of hard. Your body has been handling big weeks and long rides. A 300-plus day is a stretch, not a shock. You finish tired but intact, and you recover in days, not weeks. Same ride, completely different experience, and the only thing that changed was the base underneath it.
That's why the riders who finish centuries strong aren't necessarily the ones who did the longest single ride. They're the ones who built a CTL big enough that the century isn't the biggest thing their body has ever seen. Many riders finish a century comfortably with a CTL in the 60s to 80s. The exact number matters less than the principle: don't let the event be dramatically bigger than the training you've been absorbing.
How to build it in TrainingPeaks
So here's how to use the platform to actually get ready, rather than just hoping the Sunday rides add up.
Model the demand first. Estimate your century's TSS using the formula above — your realistic finishing time and a sensible intensity factor of around 0.68. Now you have a target: the day is going to cost you, say, 300 TSS. Everything else works backward from that.
Build CTL progressively. In the weeks before the event, you want your fitness line climbing steadily — a ramp rate of roughly 3 to 5 TSS per day per week is sustainable for most amateurs without digging a fatigue hole. That means each week's total load creeps up, with a recovery week every third or fourth week to let the adaptation land. You're not chasing a hero week. You're building a base that makes the century feel normal.
Get your long rides near the demand. The single biggest mistake is turning up to a 320-TSS event when your longest training ride was 180. That gap is where riders fall apart at mile 70. In the back half of your build, get a couple of long rides up to within striking distance of the event's TSS — not necessarily the full distance, but enough that the body has rehearsed something close to the load. The day itself should never be the biggest ride you've ever done.
Watch the chart confirm it. As the event approaches, TrainingPeaks tells you whether the base is there: a CTL that's climbed steadily, long rides whose TSS approaches the century's figure, and a fitness line that says your body is handling the kind of load the day will ask for. Then you taper — hold the fitness, shed the fatigue, and let your form swing positive for the start line, exactly the way the Performance Management Chart taper lays out.
A twelve-week build, roughly
To make it concrete, here's the shape of a sensible build for a rider starting from a modest base — say a CTL in the low 40s — aiming at a 300-TSS century.
For the first four weeks, the job is consistency, not heroics. You ride most days easy, add one longer weekend ride, and let the weekly load creep up so the CTL line starts climbing off its baseline. Your long ride might be 120 to 150 TSS by the end of this phase — nowhere near the event yet, and that's fine.
The middle four weeks are where the base gets real. The long ride grows steadily — 170, 200, 230 TSS on successive blocks, with a recovery week dropped in to absorb it. Midweek you hold a little quality: some tempo, some threshold, the work that lifts the engine rather than just enlarging it. Your CTL should be into the 60s by now, and a 200-TSS ride should feel like a normal hard day rather than a once-a-season ordeal.
The final four weeks bring the long rides within striking distance of the event — a 250 to 280 TSS day three weeks out is ideal, because it rehearses something close to the demand without being the full century. Then you ease back, let the fitness consolidate, and taper into the event. By the start line your CTL is in the 70s, your longest training rides have approached the day's cost, and 300 TSS is a stretch your body recognises rather than a shock it's never met.
That's the whole logic: don't let the event be the biggest thing your body has ever seen.
Pace it from the back end
All that fitness can still be wasted in the first hour, so a word on the day itself.
A century is paced from the back end. Target an intensity factor of around 0.65 to 0.72 for the ride as a whole, and in the first hour that will feel almost insultingly easy. That's correct. The riders who blow up are the ones who feel fresh and strong at mile 20 and ride at 0.8 because it's comfortable, then discover at mile 75 that comfortable-when-fresh and sustainable-for-six-hours are very different things. Hold yourself back early. The ride doesn't start until everyone else is hurting.
And fuel it properly — 60 to 90 grams of carbohydrate an hour, started early, because no amount of fitness survives an empty tank. The engine you spent twelve weeks building still needs feeding.
The honest version
A century isn't won on the day. It's won in the weeks of building a base big enough that a hundred miles isn't a shock to your system. The riders who suffer are the ones who fixated on the distance and ignored the demand. The riders who finish strong used the simplest tool available — the TSS on every ride, and the CTL line that adds them up — to make sure that when the day handed them its 300-point bill, they could pay it without breaking.
The number's been there on every ride you've done. Start reading it, and the century stops being a leap into the unknown and becomes the natural result of a base you can actually see.
Build the base, then time the taper with the PMC, and fuel it with the 100-mile sportive nutrition plan. If you'd rather have the whole twelve weeks built and adjusted around your numbers, come and find us on Skool.