Threshold and tempo training
Evidence: strong
Work at the second lactate threshold reliably raises the pace a runner can sustain, at low injury and recovery cost relative to harder running. The catch is definitional: “threshold” and “tempo” are used loosely, and the methods of setting the pace disagree.
Threshold work is the single most productive everyday quality session for distance runners. The aim is to spend time at or just below the lactate threshold, the intensity where blood lactate begins to accumulate faster than it clears, in order to raise the pace that can be held at that balance point. Because the velocity at threshold integrates VO₂max, running economy and the fraction of VO₂max that can be sustained, it is among the best single predictors of endurance performance, which is why the threshold is the determinant marathoners train hardest (Farrell et al. 1979; Coyle 1995).
What “threshold” actually means
The literature distinguishes two thresholds. The first (LT1, the aerobic threshold) is where lactate first rises above resting levels; the second (LT2) approximates the maximal lactate steady state (MLSS), the hardest intensity at which lactate production and clearance still balance (Faude, Kindermann & Meyer 2009). “Threshold and tempo” training usually targets the neighbourhood of LT2, which sits close to critical speed and to the pace most runners can race for roughly an hour. This is the origin of the everyday shorthand: “comfortably hard”, an effort you could sustain for about 60 minutes flat out and hold a conversation in only short phrases.
The honest difficulty is that the threshold is a region, not a line, and the ways of locating it disagree. The second threshold alone has several competing definitions, a fixed 4 mmol/L (OBLA), a fixed rise above baseline, curve-fitting methods such as Dmax, and individual-anaerobic-threshold methods, which do not all fall at the same intensity in the same runner (Faude et al. 2009). The fixed 4 mmol/L value is a convention, not a constant; real maximal lactate steady states scatter around it. So a runner setting “threshold pace” by feel, by pace from a recent race, by heart rate, or by blood lactate can arrive at four different paces, and all four are defensible. The practical upshot is to treat threshold as a narrow band and avoid drifting above it, where the cost rises faster than the benefit.
The main formats
Ways to dose the threshold
- Continuous tempo run. A sustained effort of roughly 20 to 40 minutes at threshold. In Daniels’ framework a classic tempo run is about 20 minutes of steady running at threshold pace, set from race performance via the VDOT tables (Daniels 2022).
- Cruise intervals. The same threshold dose broken into reps of 5 to 15 minutes with short recoveries of 30 to 90 seconds, which lets a runner accumulate more total time at threshold than a single continuous run, e.g. 5 × 6 min or 4 × 10 min (Daniels 2022).
- Controlled-lactate / double-threshold. The Norwegian approach holds intensity precisely in the 2.0 to 4.0 mmol/L band using regular lactate measurement, often across two sub-threshold sessions in a day, so a large volume of quality work accumulates without a single crushing effort (Kelemen et al. 2024). See double-threshold training.
The continuous and broken formats are close cousins: cruise intervals are simply a way of holding threshold pace honestly for longer, since the brief recoveries keep the pace from collapsing late in the session. The controlled-lactate variant adds measurement to enforce the cap, but the underlying stimulus is the same.
Typical dose
A common prescription is one or two threshold sessions a week, each accumulating roughly 20 to 40 minutes of quality work, at an effort around 83 to 90% of VO₂max in trained runners (Joyner & Coyle 2008; Coyle 1995). Observationally, elite distance runners run roughly 75 to 80% of training easy and spend much of the remaining intensity at or near threshold, typically across two to four threshold sessions a week (Kelemen et al. 2024). Most non-elite runners get nearly all the benefit from a single weekly tempo run run strictly to effort, layered on a base of easy volume. For how the dose shifts toward race pace as an event nears, see distance-specific training and workout types.
Why it is so productive
Threshold work delivers a large, sustainable training stimulus at relatively low cost. Holding intensity just at or below LT2 drives the oxidative adaptations, more mitochondria, denser capillaries and more lactate-transport proteins, that raise the threshold itself (Jones & Carter 2000). Because the effort is sub-maximal rather than all-out, it accumulates far more quality minutes per session than interval training near VO₂max, and it carries much less of the injury and recovery cost that limits harder work, which sits on top of the easy base as a finishing stimulus. That favourable ratio of adaptation to fatigue is the whole case for threshold work, and why it is the everyday session most distance runners build their week around. See the basics for where it fits in an overall plan.