What makes threshold training so effective
Threshold sits at a physiologically awkward intensity — hard enough to stress your aerobic system seriously, sustainable enough to accumulate meaningful time under load. That combination is what makes it so valuable. When you train at or just below your lactate threshold (what most riders know as FTP), you're pushing right at the boundary where your body has to work hard to clear lactate as fast as it's producing it. Do that repeatedly over weeks, and your body responds by shifting that boundary upward. You can hold more power before things start falling apart. That is the entire game.
The science backs this up. A 2021 study in the Journal of Strength and Conditioning Research (Jeffries et al.) found that FTP correlates strongly with the power output at a fixed blood lactate of 4.0 mmol·L⁻¹, the classical laboratory marker for threshold. A separate analysis confirmed a near-perfect correlation (r = 0.91) between FTP and maximal lactate steady state — the highest power you can sustain before lactate accumulates uncontrollably. In other words, your FTP is a reasonable proxy for the real physiological limit you're trying to push. Understanding that connection matters because it tells you why these workouts work, not just that they do. If you want a deeper look at the physiology behind all of this, the threshold training for cyclists guide covers it thoroughly.
The best threshold workouts to raise your FTP
There are really three categories of threshold work worth your attention: steady-state intervals, over-unders, and cruise intervals. Each hits slightly different mechanisms, and rotating through all three over the course of a training block produces better adaptation than hammering the same session every week.
The 2×20 is the classic. Two 20-minute efforts at 95–100% of FTP, with 5–10 minutes easy spinning in between. It sounds almost too simple, but the evidence consistently puts it at the top. The reason is volume: you're accumulating 40 minutes right at your lactate threshold, which is enough to drive real adaptation without requiring heroic fitness. For most riders, the first session feels manageable; by the third week it starts to feel like actual work. That's exactly what you want. If you're new to structured threshold training, start at the lower end of the intensity range and prioritise completing the full duration before chasing watts.
Over-unders are more demanding and more specific. The format involves alternating between efforts slightly above FTP (the "over") and slightly below (the "under") within the same interval — for example, 2 minutes at 105% FTP followed by 3 minutes at 95% FTP, repeated for 15–20 minutes. The physiological logic is sound: the above-threshold section spikes blood lactate, and the below-threshold section forces your body to clear it under fatigue. This trains the body to become as efficient as possible at metabolising lactate while still producing power — a quality that separates strong threshold riders from riders who simply have a high ceiling but poor repeatability.
Cruise intervals give you the same total training stimulus in a more fractured format, which suits athletes who struggle to complete full 20-minute blocks or who are returning from a training gap. A session of 5×8 minutes at 100% FTP with 3–4 minutes recovery achieves similar physiological stress while keeping each individual effort shorter. You can progress this format over time: 5×8 → 4×10 → 3×15 → 2×20 is a sensible ladder that spans four to six weeks of building load.
How to structure threshold sessions in your week
One to two threshold sessions per week is the right range for most amateur cyclists. More than that and recovery becomes the limiting factor — you end up doing mediocre intervals on tired legs rather than quality work on fresh ones. Less than once a week and the stimulus isn't frequent enough to drive consistent adaptation. The placement matters too. Threshold efforts belong after rest days or very easy days, not after long rides or high-intensity sessions. If you put a 2×20 at the end of a weekend of hard riding, you'll hit your power targets on paper but the physiological quality will be low.
Total threshold volume — the accumulated time spent actually at threshold intensity across a week — is a useful guide. Somewhere between 40 and 90 minutes per session is the practical working range. Below 40 minutes, the dose is probably insufficient; above 90 minutes, you're accumulating fatigue faster than adaptation. Building gradually to the higher end of that range over a four to six week block, then backing off for a recovery week, is a straightforward and effective approach. Understanding how threshold fits within your broader cycling training zones helps you keep the balance right across the full week, not just within individual sessions.
One thing worth flagging: threshold training sits in what the polarized training literature calls "Zone 2" — the moderate-intensity band between the first and second lactate thresholds. Some researchers argue this zone should be used sparingly in favour of either easy or very hard efforts. That debate is ongoing and the evidence for pure polarization over threshold-heavy training isn't conclusive for amateur cyclists. What the data does consistently show is that very high volumes of threshold work without adequate easy riding leads to accumulated fatigue and stagnation. Keep the easy days easy. The threshold sessions will feel better for it, and the gains will compound more reliably.
The mistakes that blunt your threshold gains
Going too hard is the most common one. Riders shoot for 105% FTP in a 2×20 workout, blow up after 14 minutes, then pad their power average with a massive final sprint. They feel like they worked hard. They did. But the quality of the stimulus they've delivered to their aerobic system is worse than if they'd held steady at 97–98% FTP for the full 20 minutes. Let's be honest: the ego plays a big role here. Nobody wants to log a 20-minute effort at a power that feels uncomfortable but not devastating. But threshold adaptation is built on time at the correct intensity, not peak power output during a portion of an interval.
Not progressing the load is the second mistake. Many riders do the same 2×20 session every week for a training block and wonder why their FTP doesn't move. The body adapts to specific stresses and then stops adapting unless the stress increases. That increase doesn't have to be dramatic — adding 5 watts every two or three sessions, or adding a third interval once you can complete two comfortably, is enough to keep the adaptation signal fresh.
Skipping the recovery week is the third. Four or five weeks of progressive threshold load followed by a week where you cut volume by 40–50% and keep intensity low is not a luxury — it's where the adaptation actually consolidates. Riders who skip recovery weeks tend to plateau or get sick, which sets them back further than the week they were trying to avoid taking off. If you want to understand the next step after you've built threshold capacity, how to extend time at threshold covers the progression in detail.
Threshold training done well is one of the most reliable tools in amateur cycling. The workouts aren't glamorous — there are no 30-second all-out efforts or elaborate interval structures to decode. Just sustained, uncomfortable, productive effort. Master the basics, progress the load consistently, and recover properly, and your FTP will move.
Related reads
Sources
- Jeffries O, et al. (2021). Functional Threshold Power Is Not Equivalent to Lactate Parameters in Trained Cyclists. Journal of Strength and Conditioning Research. PubMed
- Sitko S, et al. (2022). Functional Threshold Power as an Alternative to Lactate Thresholds in Road Cycling. Journal of Strength and Conditioning Research. PubMed
- Muñoz I, et al. (2019). Is the Functional Threshold Power Interchangeable With the Maximal Lactate Steady State in Trained Cyclists? International Journal of Sports Physiology and Performance. PubMed