Threshold is the hardest effort you can hold in balance — the point where the lactate your muscles produce is exactly the lactate your body can clear. A shade below it, you can go for an hour. A shade above it, the clock starts running out. Training there raises the line, and raising the line makes every effort underneath it cheaper.
That much is identical on a bike and on foot. What is not identical is how much of it you can do.
Why This Is the Bike's Best Session
A threshold run is limited by two things at once: the metabolic ceiling, and the tissue. Twenty to forty minutes of running at threshold is not just what your lactate system will take — it is also about as much hard pounding as your legs will absorb without stealing from the rest of the week. The muscular damage arrives before the metabolic stimulus runs out.
On a bike the second limit is gone. There is no landing, no eccentric loading, no muscle damage worth the name. What remains is the metabolic ceiling alone, and that ceiling sits higher. Thirty to sixty minutes of threshold work is an ordinary bike session. On foot, sixty minutes at threshold is a race.
This is the clearest example in the whole method of the same stimulus costing different amounts through different deliveries. If the fortnight owes threshold work and your legs are carrying a hard week already, the bike is not a substitute for the run — it is the better place to put it.
Why It's Broken Into Blocks
We prescribe two to four blocks of fifteen minutes, with five easy minutes between them, rather than one continuous stretch.
Physiologically, thirty minutes as two fifteens is nearly the same session as thirty minutes continuous — the five-minute break is short enough that the metabolic state you built does not fully unwind. What the break buys is quality. The last five minutes of a continuous thirty-minute block are almost always slower and sloppier than the first five, which means you spent them below threshold while feeling like you were above it. Broken into blocks, every minute of work is an honest minute of work.
There is also a reason specific to bikes. On a run, "recovery" still means running, so it is never free. On a bike you can genuinely stop pedalling, so the five minutes between blocks are true recovery rather than a slower version of the same load. That makes the broken structure meaningfully cheaper here than the equivalent structure would be on foot, and it is why the total threshold time can be so much higher.
Fifteen minutes is the block. It is long enough that the effort is genuinely sustained rather than a hard surge, and short enough that you can hold the same power in the last minute as the first. It is the most-prescribed bike interval in the sport for exactly those reasons.
Finding the Effort
Heart rate: 82 to 89% of maximum. Lower than a threshold run's 85 to 92%, for the same reason every bike band sits lower — you are seated and recruiting less muscle, so the same effort produces a lower heart rate. Do not chase your running threshold number here.
Feel: comfortably hard. You can speak in short phrases, not sentences. Breathing is deep and rhythmic but controlled. There is no sense of a countdown — if you are counting down, you are above threshold.
Cadence: 85 to 95 rpm, the same as an easy ride. Threshold is not the place to grind. A big gear at 70 rpm turns a metabolic session into a muscular one and changes what you are training.
Heart rate lags. It takes two to three minutes to arrive at the band. Pace the first block by feel and let the number confirm it, rather than pushing to reach a target that has not caught up yet. This is the single most common way to ruin block one.
Do It on a Climb If You Have One
A long steady climb is the ideal place for these blocks. It removes the two things that make threshold hard to hold on flat roads — junctions and the temptation to freewheel — and the constant resistance means the effort stays honest without you managing it.
The gradient wants to be shallow enough to spin, roughly three to six percent. Steeper than that and cadence collapses and the session drifts muscular. A five-minute descent between blocks is a perfect recovery.
We do not prescribe a separate "hill session" on the bike, because there isn't one. A sustained climb is a threshold block with the resistance provided by gravity instead of by gear choice — same physiology, same heart rate, same instruction. If a climb is what you have, use it.
Common Mistakes
Starting block one too hard. Almost universal. You feel fresh, the heart rate has not risen yet, so you push. Block three then falls apart and the session's total quality time is lower than if you had been patient.
Riding the recoveries. Five minutes means five easy minutes. Soft-pedalling at 200 watts because you are on a nice road defeats the purpose of breaking the blocks up at all.
Treating it as a test. This is a training session, not a measurement. The aim is to finish all the blocks at the same effort, not to find out how hard block one can be.
Doing it the day before or after a hard run. Threshold on a bike costs your central and hormonal systems what threshold on foot costs them. It is gentle on the legs, not on the athlete. Space it like any other quality session.
Practical Guidelines
- Structure: 15 minute warm-up · 2 to 4 × 15 minutes at threshold, 5 easy minutes between · 10 minute cool-down.
- Total: 60 to 100 minutes.
- Intensity: 82 to 89% of maximum heart rate. RPE 7. Short phrases only.
- Cadence: 85 to 95 rpm throughout, blocks included.
- Frequency: once a week at most, and never adjacent to another quality session.
- Indoors is ideal. No junctions, no descents, no traffic — the block is uninterrupted, which is exactly what it needs.