Builds three or five training zones from a first (LT1) and a second (LT2) lactate threshold, with the zone boundaries placed at the boundaries of the exercise intensity domains: below LT1 is the moderate domain, from LT1 to LT2 the heavy domain, and above LT2 the severe domain (Jamnick et al., 2020). You choose which thresholds mark LT1 and LT2.
Arguments
- x
The result of
lactate_threshold().- lt1, lt2
The thresholds that mark LT1 and LT2: a method in
x$method, or an intensity. Default to those chosen inlactate_threshold(), which are"Bsln + 0.5"and"Log-Poly-ModDmax"unless you set them; seeDetails.- model
The number of zones:
3(default) or5.- split
How to split the moderate and severe domains in the five-zone model:
"relative"(default),"seiler", or two intensities. Ignored with three zones.- object
The result of
lactate_zones().- heart_rate
How the plot shows the heart rate of the stages, when the test has it:
"panel"(default), in a panel under the curve on the same intensity axis, read at LT1 and LT2;"axis", on the lactate plot against a second axis, as many lab reports do; or"none".options(lactater.heart_rate = "axis")sets it for every plot and report.- view
"curve"(default), the zones on the lactate curve; or"ruler", one bar of the zones over the intensity, pace, heart rate and RPE at each boundary, to hand to the athlete.- ...
Not used.
Value
a lactate_zones tibble with one row per zone: zone, domain, description, intensity_from,
intensity_to, the matching pace range (running, swimming, rowing), the lactate range on the fitted curve
(NA at a boundary outside the stages, where the curve is not extrapolated), and the heart_rate and rpe ranges
(when available; a boundary below the first stage is extrapolated from the first three stages). The first zone has
no lower bound and the last no upper bound.
Plot it with autoplot().
Details
Three zones (
model = 3): zone 1 below LT1, zone 2 from LT1 to LT2, zone 3 above LT2 (Hofmann & Tschakert, 2017).Five zones (
model = 5): zones 1 and 2 split the moderate domain, zone 3 is the heavy domain, and zones 4 and 5 split the severe domain, as in the five-zone scale described by Seiler (2010) and Tonnessen et al. (2014), where zones 1-2 lie below LT1, zone 3 between LT1 and LT2, and zones 4-5 above LT2. The two splits inside a domain are set bysplit. The five zones are not named: the scale gives them no names, and the names of other scales belong to other boundaries (the "threshold" level of the five-level scale in Jamnick et al., 2020, Table 1, lies around LT2, not above it). The two splits:"relative"(default): zone 1|2 at 75% of LT1, and zone 4|5 halfway between LT2 and the highest intensity of the test. In the five-zone scale of Seiler (2010, Table 1), zone 2 starts at 66% of the maximal oxygen uptake and zone 3 at 81%; converted with the oxygen cost of cycling and running (Glass & Dwyer, 2007), our own calculation, that puts zone 2 at about 77% of the power at LT1 and 80% of the running speed. Sitko et al. (2025) place zone 2 "immediately below" LT1, at about 80% to 90% of the heart rate at LT1, which on the cycling tests of lactate_tests (our count, where that heart rate falls within the stages) starts it at a median of about 65% of the power at LT1. 75% lies between the two and needs no heart rate. Zone 5 starts at 94% of the maximal oxygen uptake, halfway between the start of zone 4 (88%) and the maximum. Both cuts are approximations: no physiological marker separates them (Bishop et al., 2025), and the scale's zones are "somewhat arbitrary" (Seiler, 2010)."seiler": where the fitted curve reaches 1.5 mmol/L (zone 1|2) and 6.0 mmol/L (zone 4|5), the blood lactate limits of the five-zone scale in Seiler (2010). A cut that falls outside its domain, or is not reached, uses the relative split instead, with a warning.Two intensities,
c(zone 1|2, zone 4|5), for your own cuts.
LT1 is usually a "first rise" threshold ("Log-log", "Bsln + 0.5", "Bsln + 1.0", "LTratio", "LTP1"), and
LT2 a threshold aimed at the maximal lactate steady state (MLSS) or the second, abrupt rise (the Dmax family,
"LTP2", "IAT", "Stegmann", "Keul" and "Simon" (running), and "Bsln + 1.5", which estimated the MLSS
in two studies; Jamnick et al., 2020).
These are two of the three categories of threshold concepts of Faude et al. (2009); fixed values such as
"OBLA 4.0" are the third. Against a measured MLSS these landed from about 40 W below to 40 W above it on average,
by
method, protocol and athletes (Hauser et al., 2014; Ploszczyca et al., 2020), and whether the MLSS or the critical
power marks the boundary between the heavy and severe domains is debated (Jones et al., 2019). Different choices
give different zones, so report which ones you used.
The default pair has the best evidence for each boundary and moves least with a single stage. Bsln + 0.5 is among
the most defensible markers of the moderate-heavy boundary (Jamnick et al., 2020), and Log-Poly-ModDmax estimated the
MLSS with 4-min stages (Jamnick et al., 2018). Left out one stage at a time on the cycling tests of
lactate_tests, Bsln + 0.5 moved by a median 1.7% (jackknife standard error) and Log-Poly-ModDmax by 8.6%, against
23% for LTP1, whose three-segment fit has few stages to spare in a step test. Bsln + 0.5 rests on a single baseline
sample, so check that sample (see lactate_diagnostics()).
References
Faude O, Kindermann W, Meyer T. Lactate threshold concepts: how valid are they? Sports Medicine. 2009;39(6):469-490.
Hofmann P, Tschakert G. Intensity- and duration-based options to regulate endurance training. Frontiers in Physiology. 2017;8:337.
Bishop DJ, Beck B, Biddle SJH, et al. Physical activity and exercise intensity terminology: a joint American College of Sports Medicine (ACSM) expert statement and Exercise and Sport Science Australia (ESSA) consensus statement. Medicine & Science in Sports & Exercise. 2025;57(11):2599-2613. doi:10.1249/MSS.0000000000003795
Glass S, Dwyer GB, editors. ACSM's metabolic calculations handbook. Baltimore: Lippincott Williams & Wilkins; 2007.
Hauser T, Adam J, Schulz H. Comparison of selected lactate threshold parameters with maximal lactate steady state in cycling. International Journal of Sports Medicine. 2014;35(6):517-521.
Jamnick NA, Botella J, Pyne DB, Bishop DJ. Manipulating graded exercise test variables affects the validity of the lactate threshold and VO2peak. PLOS ONE. 2018;13(7):e0199794.
Jamnick NA, Pettitt RW, Granata C, Pyne DB, Bishop DJ. An examination and critique of current methods to determine exercise intensity. Sports Medicine. 2020;50(10):1729-1756.
Jones AM, Burnley M, Black MI, Poole DC, Vanhatalo A. The maximal metabolic steady state: redefining the 'gold standard'. Physiological Reports. 2019;7(10):e14098.
Ploszczyca K, Jazic D, Piotrowicz Z, Chalimoniuk M, Langfort J, Czuba M. Comparison of maximal lactate steady state with anaerobic threshold determined by various methods based on graded exercise test with 3-minute stages in elite cyclists. BMC Sports Science, Medicine and Rehabilitation. 2020;12:70.
Seiler S. What is best practice for training intensity and duration distribution in endurance athletes? International Journal of Sports Physiology and Performance. 2010;5(3):276-291.
Sitko S, Artetxe X, Bonnevie-Svendsen M, et al. What is "zone 2 training"?: experts' viewpoint on definition, training methods, and expected adaptations. International Journal of Sports Physiology and Performance. 2025;20(11):1614-1617. doi:10.1123/ijspp.2024-0303
Tonnessen E, Sylta O, Haugen TA, Hem E, Svendsen IS, Seiler S. The road to gold: training and peaking characteristics in the year prior to a gold medal endurance performance. PLOS ONE. 2014;9(7):e101796.
Examples
results <- lactate_threshold(demo_data, intensity, lactate, heart_rate, plot = FALSE)
lactate_zones(results)
#> # A tibble: 3 × 9
#> zone domain description intensity_from intensity_to lactate_from lactate_to
#> <chr> <chr> <chr> <dbl> <dbl> <dbl> <dbl>
#> 1 Zone 1 modera… below LT1 NA 83 NA 1.4
#> 2 Zone 2 heavy LT1 to LT2 83 149 1.4 4.2
#> 3 Zone 3 severe above LT2 149 NA 4.2 NA
#> # ℹ 2 more variables: heart_rate_from <dbl>, heart_rate_to <dbl>
lactate_zones(results, model = 5)
#> # A tibble: 5 × 9
#> zone domain description intensity_from intensity_to lactate_from lactate_to
#> <chr> <chr> <chr> <dbl> <dbl> <dbl> <dbl>
#> 1 Zone 1 modera… below LT1 NA 62 NA 1.1
#> 2 Zone 2 modera… below LT1 62 83 1.1 1.4
#> 3 Zone 3 heavy LT1 to LT2 83 149 1.4 4.2
#> 4 Zone 4 severe above LT2 149 170 4.2 6.1
#> 5 Zone 5 severe above LT2 170 NA 6.1 NA
#> # ℹ 2 more variables: heart_rate_from <dbl>, heart_rate_to <dbl>
lactate_zones(results, lt1 = "Log-log", lt2 = "ModDmax", model = 5, split = "seiler")
#> # A tibble: 5 × 9
#> zone domain description intensity_from intensity_to lactate_from lactate_to
#> <chr> <chr> <chr> <dbl> <dbl> <dbl> <dbl>
#> 1 Zone 1 modera… below LT1 NA 86 NA 1.5
#> 2 Zone 2 modera… below LT1 86 101 1.5 1.8
#> 3 Zone 3 heavy LT1 to LT2 101 140 1.8 3.6
#> 4 Zone 4 severe above LT2 140 169 3.6 6
#> 5 Zone 5 severe above LT2 169 NA 6 NA
#> # ℹ 2 more variables: heart_rate_from <dbl>, heart_rate_to <dbl>