Why Every Masters Cyclist Should Test Durability (Not Just FTP)
Why some riders fall apart after 1,500 kJ — and what to do about it
By Ric Stern
Most cyclists put far too much weight on a single number: FTP. It is a useful benchmark, but it only tells you how strong you are when you are relatively fresh. It tells you nothing about how strong you are after you have already done a significant amount of work.
For riders over 40, that distinction really matters. Gran fondos, gravel events, hilly sportives and long club runs are not decided in the first hour. They are decided after several hours of riding, when everyone is tired and the ability to keep producing power under fatigue becomes the real limiter.
That quality has a name: durability.
Durability is your ability to maintain a high percentage of your best power after you have accumulated a large amount of work, usually expressed in kilojoules (kJ). It is a very different thing from FTP, and in many masters riders it is the true weak point.
What durability actually is
Durability is simply the relationship between what you can do when you are fresh and what you can do when you are already tired.
If you ride a 20-minute best effort at the start of a session and then repeat the same test after several hours of riding, the drop in average power between those two efforts is a measure of your durability. A small drop means you are good at holding performance when fatigued. A large drop means you are not.
This is not an abstract lab concept. It is exactly what happens in real rides and races. The rider who can still produce close to their “fresh” power after a long day is the rider who climbs best at the end, who rides away from the group, or who simply doesn’t implode in the last hour.
A reality check from a 56-year-old
To make this concrete, I’ll use myself as an example.
I’m 56. My numbers are decent. I am still competitive. But if I look at my files honestly, I start to see a clear pattern: once I have done around 1,500 kJ of work, my ability to hold high power starts to fall away faster than I would like.
Part of that is physiology. Durability tends to get worse with age unless you train it specifically. Part of it is fuelling. I have historically been poor at taking in enough carbohydrate on the bike. By contrast, my partner Claire has much better fat oxidation, and she is disciplined with on-bike nutrition. After seven hours, she is still riding strongly while I am hanging on.
That is not because she has more talent. It is because her durability is better trained and better fuelled.
The point is not that 1,500 kJ is “good” or “bad”. The point is that for most masters riders, the “falling apart point” is much earlier than the pro-level numbers you see thrown around online. And the good news is that it can be improved.
The 3,000 kJ myth (and what matters for normal people)
You may see elite-level discussions about riders producing race-winning efforts after 3,000 kJ of work, or even 5,000 kJ for WorldTour pros. Those numbers are meaningful in professional long-distance racing where the real move often happens after hours of hard riding.
But for most trained amateur and masters cyclists, the meaningful durability point happens much earlier:
Recreational riders (<5 hours/week): durability often drops after 1,000–1,500 kJ
Trained masters cyclists (6–10 hours/week): many start fading around 1,500–2,000 kJ
Stronger amateur racers: 2,000–3,000 kJ
WorldTour professionals: capable of decisive efforts after 3,000–5,000 kJ
There is nothing “bad” or “good” about your number — it simply tells you where your durability curve currently sits, and therefore where you can improve it.
How to test your durability (without a lab)
You do not need a fancy protocol. Two simple tests with a power meter will tell you a lot.
Test 1 – fresh power
On the first day:
Warm up for 20–30 minutes.
Ride a 20-minute all-out effort, paced like a time trial.
Record your average power for those 20 minutes.
That gives you a good benchmark for what you can do when you are comparatively fresh.
Test 2 – fatigued power
On another day, ideally in similar conditions:
Ride at endurance pace in Zone 2. You should feel comfortable and controlled, not smashing it.
Continue until your head unit shows a sensible target for you. For many masters riders that will be around 1,500 kJ; for less trained riders 1,000–1,200 kJ is fine; for stronger riders 2,000 kJ may be appropriate.
Spin very gently for 5–10 minutes.
Repeat the same 20-minute all-out effort.
Compare the average power to your fresh test.
Now look at the drop-off:
If the second effort is within about 5% of the first, your durability is excellent.
A drop of 5–10% is very common and still leaves a lot of room to improve.
A drop of 10–15% suggests durability is a clear limiter.
Anything more than that means it is almost certainly the thing holding you back on long rides and races, not your absolute FTP.
This takes a bit of effort, but it gives you a far more realistic picture of how you perform in the real world than yet another FTP test.
What actually improves durability
One of the big mistakes in the “3,000 kJ” conversation is the idea that you fix durability simply by doing more long rides and chasing big kJ numbers on your head unit. Long rides are part of the picture, but they are not the whole story.
For masters cyclists, durability improves when several pieces come together.
First, you need a strong aerobic base.
This comes from genuine Zone 2 work, not half-hard riding that drifts into tempo. If you use my training levels, that means sitting around 50–65% of your MAP for sustained periods. This is where you build more mitochondria, better capillary density, and improved fat oxidation. It is also where you learn to ride for two to four hours without turning everything into a threshold session.
Second, you need some MIET.
MIET sessions, done sensibly, help you hold a reasonably high percentage of threshold for longer, and they teach your system to tolerate steady load without blowing up. For most masters riders, one or two MIET sessions per week is plenty.
Third, strength training matters.
Durability is not just about metabolism; it is also about neuromuscular resilience. If you lose the ability to produce force late in a ride, your power will fall even if your heart and lungs are fine. Strength work for the legs and trunk helps you maintain posture, torque and stability deep into a long day.
It is important that you put the bike first. On days where you combine hard cycling and strength, do the quality bike session earlier, then lift several hours later. Doing heavy squats and then trying to hit high power numbers rarely ends well for a masters rider.
Fourth, fuelling is critical.
Most riders over 40 under-fuel almost every long ride they do. That is one of the fastest ways to destroy durability. If you want to ride strongly after 1,500–2,000 kJ of work, you need to start taking in carbohydrate early and consistently, aiming for around 60–90 grams of carbohydrate per hour on longer rides. That is not gluttony; it is what your muscles and brain actually need to keep performing.
Fifth, you can use “fatigued-then-hard” sessions sparingly.
Once you have built some base fitness and you are fuelling properly, it can be very effective to do occasional rides where you accumulate a sensible amount of work first and then add intervals at the end.
For example, you might ride Zone 2 for two to three hours, reach around 1,400–1,800 kJ, then complete a small block of threshold or VO₂max intervals before calling it a day. These sessions teach your body and brain to produce quality efforts while tired. They do not need to be done every week; every 10–14 days is enough for most masters riders.
A simple four-week durability block
Here is a straightforward way to start training durability without overcomplicating things. This assumes you are already riding several times per week.
Week 1: Do one long Zone 2 ride that takes you to around 1,400 kJ. In the last part of the ride, add two intervals of eight minutes at MIET, with easy riding between them.
Week 2: Repeat the idea, but extend the long ride to around 1,600 kJ and finish with three intervals of six minutes at 95–100% of FTP.
Week 3: Increase the long ride to about 1,800 kJ and finish with four intervals of three minutes at roughly 105–110% of FTP.
Week 4: Make this a recovery week. Keep your rides shorter and easier, and include just one light MIET session rather than a long durability ride.
If you combine that with one other quality session in the week (another MIET or VO₂max session), some easier endurance work and sensible strength training, you will usually see a noticeable improvement in late-ride power within four to six weeks.
Common mistakes
There are a few traps that masters riders fall into repeatedly when they start thinking about durability.
The first is trying to jump straight to “pro numbers”, such as 3,000 kJ, when their current limit is 1,200–1,500 kJ. That is a fast track to over-reaching and frustration. It is far better to start where you are and progress gradually.
The second is treating kJ as the goal rather than as context. Kilojoules are simply a measure of how much work you have done. They do not tell you anything about whether you rode at the right intensity, or whether the session matched your current needs.
The third is under-fuelling, which I have been guilty of myself. If you do not eat enough, you are teaching your body to stop producing power early, not to go longer.
The fourth is trying to do a long durability ride every week, on top of other hard sessions, without enough recovery. Masters riders usually respond better to slightly less frequent but higher-quality work.
The fifth is assuming that simply riding long is enough. Long rides are useful, but without appropriate intensity distribution, fuelling and progression, they can become a way to practise getting tired rather than a way to build durability.
Pulling it together
Durability is not about macho screenshots of huge kJ numbers. It is about whether you can still ride well when it really matters — in the last hour of a long day, not the first.
For most riders in their 40s, 50s and 60s, it is the missing piece. Their FTP is fine. Their VO₂max is fine. What lets them down is the ability to produce a decent percentage of those numbers once they have accumulated 1,500–2,000 kJ of work.
The good news is that durability is very trainable. Build a solid aerobic base. Add structured MIET. Use strength training intelligently. Fuel properly. Occasionally ask your body to produce quality under fatigue. Do those things consistently and you will not just ride further; you will ride stronger at the very point where everyone else is fading.
If durability is your limiter, the training inside The Collective will fix that.
Structured plans, coaching support, education, and a community that keeps you accountable.
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