How long should a Zone 2 run be?
An easy Zone 2 run is 45 to 75 minutes. A long run is 90 to 120.
Set the run in time, not distance. Your Zone 2 range sets the pace, so the distance you cover is an output. A recovery run is the bottom of the range.
How many Zone 2 runs a week should you do?
Three to four Zone 2 runs a week, one of them the long run.
Three or four easy runs fill the easy majority of a week that also holds one or two hard sessions and a day off. Three is the week with more hard work in it or less time. Four is the week where an extra easy run still fits without crowding the hard days. Which days is up to you. The long run takes the day with the most time in it.
Public-health guidance says the same: spread your aerobic minutes across the week rather than stacking them.
Here's how those runs add up over eight weeks:
What does an 8-week Zone 2 base plan look like?
Build an aerobic base you can keep. Most of the running is easy Zone 2, with one hard session a week and a long run that grows to two hours.
How much of your running should be Zone 2?
Most of it: at least 70% of your running volume, and the runners at the top of the sport hold 80% or more.
A systematic review of middle- and long-distance runners' training put the floor there. Its conclusion: at least 70% of volume at low intensity and at most 30% at threshold and above is necessary to optimize endurance adaptation. A study of world-class distance runners' training puts at least 80% of their total running volume at low intensity through the year. Low intensity is the bottom two of that study's seven zones.
The "80/20" label counts sessions, not hours: about 80% of training sessions at low intensity, in elite endurance athletes training 10 to 13 times a week. On three or four runs a week, the easy runs are the long ones, so most of your minutes are easy as long as they stay easy.
In a small heart-rate-controlled trial of sub-elite runners, the group that kept more of its running easy improved a simulated race more. The gap between most recreational runners' weeks and that shape has been measured in marathon training logs.
Does walking count as Zone 2?
Yes. Zone 2 is an intensity, not a gait. Any movement that holds your heart rate in the zone is Zone 2 training, brisk walking and incline walking included.
The zone sits just below the first lactate threshold. The 2025 expert panel that defined it that way says its methods carry across endurance sports. The criterion is the number on your chest strap or watch. There is no Zone 2 walking speed and no incline setting that makes a walk count: whatever holds the heart rate in the zone is in.
What walking does less well is build the running. The payoff of Zone 2 running is a faster pace at the same heart rate, and that comes from running. In a trial of well-trained runners, adding running improved a running time trial more than the same training load in another sport did.
Here's why holding the zone can take walking at first:
Why is my easy run heart rate so high?
Because the run isn't as easy as it feels. Slow down, keep at it, and the pace you can hold in Zone 2 rises.
How do you do Zone 2 on a treadmill?
The same way as outside: set the zone by heart rate and let the belt speed be whatever holds it. Zone 2 by heart rate on a treadmill counts.
At the same easy or moderate speed, treadmill heart rate sits within a few BPM of outdoor running. That's pooled across crossover studies that ran the same people on both.
What changes is pace. The belt's display, your watch, and your own sense of effort report a treadmill run's pace three different ways, and none of them measures you.
So there is no Zone 2 treadmill speed. The heart rate sets the speed, and an incline just lowers the speed that holds it. The speed that holds the zone rises as the base builds.
How do you stay in Zone 2 on hills?
Hold the heart rate and let the pace go. Slow on the climb until the number settles, and walk the climb if slowing isn't enough. Let the descent come back faster at the same heart rate.
Running the same speed uphill costs more energy per meter and downhill less, measured across steep treadmill gradients in runners. So the same pace up a hill is a harder effort and the same pace down it is an easier one. A slower average on a hilly route with the zone held the whole way is the run done right.
The climb is where the number moves under you fastest, and the wrist is the last place you can look. RunBeat's Zone Training calls the slow-down in your ear as the climb pushes the number up, no look at the wrist needed:
How do you stay in Zone 2 in the heat?
Slow down from the start. Warm air raises heart rate at the same pace, so the same zone means a slower pace on a hot day.
One study had 14 trained cyclists ride 45 minutes at 70% of VO₂ peak in air from 18 to 36°C, humidity matched: heart rate rose about 1 BPM per degree.
The heat offset shows up early in the run. That's a different thing from the slow climb of heart rate over a long run, which happens in cool weather too.
Run in the cooler part of the day where you can, and expect walk stretches a cool day wouldn't need.
Sources
- Haugen T, Sandbakk Ø, Seiler S, Tønnessen E. The Training Characteristics of World-Class Distance Runners: An Integration of Scientific Literature and Results-Proven Practice. Sports Medicine - Open. 2022;8:46. doi:10.1186/s40798-022-00438-7. 59 world-leading athletes and 16 coaches. Source for the at-least-80% low-intensity share (zones 1 and 2 of the paper's seven-zone scale). Elite practice, never a target; the paper's session counts, weekly distances, and run durations are not stated here.
- Campos Y, Casado A, Vieira JG, et al. Training-intensity Distribution on Middle- and Long-distance Runners: A Systematic Review. International Journal of Sports Medicine. 2022;43(4):305-316. doi:10.1055/a-1559-3623. 20 studies. Source for the at-least-70% low-intensity floor and the at-most-30% share at threshold and above, stated as the review's conclusion.
- 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. doi:10.1123/ijspp.5.3.276. Source for the about-80%-of-sessions figure behind the "80/20" label; sessions, not time, in elite athletes training 10 to 13 times a week.
- Esteve-Lanao J, Foster C, Seiler S, Lucia A. Impact of training intensity distribution on performance in endurance athletes. Journal of Strength and Conditioning Research. 2007;21(3):943-949. doi:10.1519/R-19725.1. 12 sub-elite runners, five months, heart-rate-controlled, a three-zone model. Stated qualitatively; no figure from it appears here.
- Physical Activity Guidelines for Americans, 2nd edition. U.S. Department of Health and Human Services, 2018. Source for the preferably-spread-through-the-week clause. The guideline prescribes moderate-intensity aerobic activity and names no zone; reading it onto Zone 2 runs is this page's own.
- Sitko S, 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. doi:10.1123/ijspp.2024-0303. Invited expert viewpoint, a cycling-focused panel of 14. Source for the definition by intensity (just below the first lactate or ventilatory threshold) and the panel's statement that its methods apply to other endurance sports with modification; no heart rate or lactate figure from it appears here.
- Foster C, Hector LL, Welsh R, Schrager M, Green MA, Snyder AC. Effects of specific versus cross-training on running performance. European Journal of Applied Physiology. 1995;70(4):367-372. doi:10.1007/BF00865035. 30 well-trained runners, eight weeks; the added cross-training was swimming. Source for the direction only: specific training improved the running time trial more than the same load of a dissimilar sport. Swimming is a dissimilar mode and walking a similar one, so the study licenses the direction for walking and no magnitude.
- Miller JR, Van Hooren B, Bishop C, Buckley JD, Willy RW, Fuller JT. A systematic review and meta-analysis of crossover studies comparing physiological, perceptual and performance measures between treadmill and overground running. Sports Medicine. 2019;49:763-782. doi:10.1007/s40279-019-01087-9. Source for treadmill heart rate staying within a few BPM of outdoor running at the same easy or moderate speed; the pooled estimates carry high heterogeneity, so no tighter figure is stated.
- Minetti AE, Moia C, Roi GS, Susta D, Ferretti G. Energy cost of walking and running at extreme uphill and downhill slopes. Journal of Applied Physiology. 2002;93(3):1039-1046. doi:10.1152/japplphysiol.01177.2001. 10 runners on a treadmill across steep gradients. Source for the direction only: the energy cost of running a given speed rises uphill and falls downhill. The paper states costs at the level and the extremes, so no mid-gradient figure is printed, and no published primary converts a gradient to a heart-rate rise for running.
- Jenkins EJ, Campbell HA, Lee JKW, Mündel T, Cotter JD. Delineating the impacts of air temperature and humidity for endurance exercise. Experimental Physiology. 2023;108(2):207-220. doi:10.1113/EP090969. 14 trained participants cycling 45 minutes at 70% of VO₂ peak at 18, 27, and 36°C at matched absolute humidity. Source for the about-1-BPM-per-degree heart-rate slope, stated as the abstract states it; the paper does not describe how the slope was fitted, and it is not a per-degree rule for a reader. Cycling above the Zone 2 band; the direction transfers, the magnitude is the study's.
- Arngrímsson SA, Stewart DJ, Borrani F, Skinner KA, Cureton KJ. Relation of heart rate to percent VO₂ peak during submaximal exercise in the heat. Journal of Applied Physiology. 2003;94(3):1162-1168. doi:10.1152/japplphysiol.00508.2002. 22 runners walking 20 minutes at about a third of VO₂ max at 25 to 45°C. Corroborates the direction in runners; temperatures beyond running conditions, no figure stated here.