Quick Answer
5 zones based on % max heart rate. Zone 2 (60–70% max HR) = easy aerobic base — where most of your training should be. Zone 4 (80–90% max HR) = lactate threshold — highest-return hard work. 80/20 rule: 80% of training in Zones 1–2, 20% in Zones 4–5, minimal Zone 3. Zone 3 (“grey zone”) accumulates fatigue without producing optimal adaptation from either direction.
The 3-Zone Model vs the 5-Zone Model: Understanding Both
Before diving into the five zones most runners use, it’s worth understanding where zone models come from — because the same language (Zone 1, Zone 2, etc.) means different things depending on which system is being referenced.
Exercise physiologist Stephen Seiler at the University of Agder in Norway established the foundational three-zone model based on two key physiological thresholds: the aerobic threshold (the upper boundary of truly easy effort, where fat oxidation is dominant and lactate remains near baseline) and the lactate threshold (above which lactate accumulates faster than the body can clear it). In this three-zone model: Zone 1 is below the aerobic threshold (easy, conversational); Zone 2 is between the aerobic and lactate thresholds (comfortably hard); and Zone 3 is above the lactate threshold (very hard, interval-intensity).
The five-zone model — used by Polar, Garmin, Joe Friel’s Training Bible system, and most running coaches — subdivides this framework with greater practical resolution. Zones 1–2 in the five-zone model both map to Seiler’s Zone 1 (below aerobic threshold). Zone 3 in the five-zone model sits roughly between the thresholds. Zones 4–5 sit above the lactate threshold.
This distinction matters because the research Seiler conducted — the famous 80/20 finding — uses his three-zone model. When Seiler says elite athletes spend 80% of training in “Zone 1,” he means everything below the aerobic threshold, which includes what most runners label as Zones 1 and 2. The practical implication: the 80/20 rule means 80% in the five-zone model’s Zones 1–2, 20% in Zones 4–5, and minimal time in Zone 3.
The Five Running Zones: What Each Does
| Zone | % Max HR | Feel | Primary purpose | Typical sessions |
|---|---|---|---|---|
| Zone 1 | 50–60% | Very easy; can sing; barely elevated breathing | Active recovery; warmup/cool-down | Recovery jog, warm-up, cool-down, rest day movement |
| Zone 2 | 60–70% | Conversational; full sentences without effort; can breathe through nose | Aerobic base; fat oxidation; mitochondrial density | Easy runs, long runs, aerobic base building |
| Zone 3 | 70–80% | Comfortably hard; short sentences; moderate breathing | Aerobic endurance; avoid overusing (grey zone) | Moderate effort runs; some marathon-pace work |
| Zone 4 | 80–90% | Hard; few words at a time; noticeably laboured breathing | Lactate threshold; fastest sustainable pace | Tempo runs, cruise intervals, threshold sessions |
| Zone 5 | 90–100% | Maximum; cannot speak; breathing at or near limit | VO2max; anaerobic capacity; top-end speed | Short intervals, 5K race effort, sprint repeats |
Zone 1: Recovery
Zone 1 is used for active recovery — movement that increases blood flow without creating meaningful training stress. It’s the appropriate zone for warm-up, cool-down, and easy recovery days between hard sessions. Most runners spend very little intentional time in Zone 1 beyond warm-ups, but it’s valuable: recovery runs at genuine Zone 1 effort accelerate lactate clearance and reduce muscle soreness more effectively than complete rest without adding fatigue. Our warm-up and cool-down guide covers the Zone 1 effort that bookends quality sessions.
Zone 2: The Aerobic Base — Where Most Running Should Happen
Zone 2 is the most important zone for endurance runners, and the most consistently misunderstood and underutilised. At 60–70% of maximum heart rate, Zone 2 effort feels genuinely easy — full conversation is comfortable, breathing is slightly elevated but not laboured, and the pace is slower than most runners’ ego is comfortable with.
This is where the primary aerobic adaptations happen: mitochondrial density increases (mitochondria are the cells’ energy-producing organelles — more and larger mitochondria mean more aerobic energy at faster paces), fat oxidation efficiency improves (reducing dependence on limited glycogen stores at race effort), stroke volume increases (the heart pumps more blood per beat), and capillary density in running muscles grows. These adaptations accumulate slowly over months and form the aerobic base that makes all other training more effective.
The most common Zone 2 mistake is running too fast. Most recreational runners default to an effort that feels like it has purpose — slightly laboured breathing, some effort required — which lands them in Zone 3, not Zone 2. If you’re running and can only speak in short phrases, you’ve already drifted above Zone 2. Our easy run effort guide covers exactly what Zone 2 should feel like — and why most runners find true Zone 2 embarrassingly slow when they first start training by heart rate.
Zone 3: The Grey Zone (Use Sparingly)
Zone 3 is the most problematic zone in recreational running training — not because it’s harmful, but because most runners spend far too much of their training here, and it produces inferior results relative to the fatigue it creates.
The problem is physiological: Zone 3 is too hard to be optimal for aerobic base development (Zone 2 produces better mitochondrial and capillary adaptations at lower fatigue cost) and not hard enough to drive the lactate threshold or VO2max adaptations that Zones 4 and 5 produce. It sits in a middle ground that accumulates meaningful fatigue — it’s genuinely hard — without a distinct enough physiological signal to produce the adaptation that the effort demands. Polar describes Zone 3 as where “pushing harder doesn’t always produce better results” and notes that excessive Zone 3 time “can cause fatigue without maximising aerobic gains and may compromise day-to-day recovery.”
Zone 3 is not useless — marathon-pace running for experienced runners sits in Zone 3, and some tempo work is appropriate in this zone. But it should be a small proportion of total training rather than the default effort. The polarised training model explicitly limits Zone 3 to less than 10% of weekly volume.
Zone 4: Lactate Threshold — Highest-Return Hard Work
Zone 4 is where the most race-specific adaptation occurs for distances from 5K to marathon. At 80–90% of maximum heart rate, this is lactate threshold effort — the fastest pace at which the body can maintain rough lactate equilibrium. Training at and near this intensity teaches the body to clear lactate more efficiently, raises the threshold itself (allowing faster sustained paces before fatigue), and develops the mental capacity to sustain discomfort at race effort.
Zone 4 corresponds to the “comfortably hard” tempo run effort and threshold intervals covered in depth in our lactate threshold guide. Sessions in Zone 4 should feel like 7–8 out of 10 effort — hard but controlled, maintaining form throughout without the session falling apart in the final repetitions. Heart rate in Zone 4 is typically 80–90% of maximum, or approximately 83–88% of lactate threshold heart rate (LTHR).
Zone 5: VO2max and Anaerobic
Zone 5 (90–100% max HR) is the territory of short, maximal intervals — the kind that produce VO2max adaptation and develop the top-end speed that determines how fast the ceiling of performance sits. At this intensity, the body cannot sustain effort beyond a few minutes; recovery between intervals is essential. This is the zone of 400m and 800m track intervals, short hill sprints, and Tabata-style sessions.
Zone 5 work is the 20% that pairs with Zone 2 in the 80/20 model. It should be genuinely hard — not a forced-easy version of hard — and recovery should be sufficient to maintain quality across all repetitions. Our VO2 max workouts guide covers the specific interval protocols that target this zone most effectively.
How to Calculate Your Running Zones Accurately
The accuracy of your training zones depends entirely on the accuracy of your maximum heart rate. The simple 220 minus age formula has a standard error of ±10–12 beats per minute — meaning for many individuals it can be significantly wrong in either direction, producing zones that are either too easy or too hard.
The Karvonen Formula (Heart Rate Reserve Method) is considerably more accurate because it accounts for your resting heart rate, which reflects individual cardiovascular fitness:
Step 1: Find maximum heart rate (field test or formula). Step 2: Measure resting heart rate (lowest reading taken over several mornings before getting out of bed). Step 3: Heart Rate Reserve (HRR) = max HR − resting HR. Step 4: Target zone HR = (HRR × zone %) + resting HR.
Worked example: Runner with max HR 185, resting HR 55. HRR = 130. Zone 2 (60–70%): lower boundary = (130 × 0.60) + 55 = 133 bpm; upper boundary = (130 × 0.70) + 55 = 146 bpm. Zone 4 (80–90%): lower = (130 × 0.80) + 55 = 159 bpm; upper = (130 × 0.90) + 55 = 172 bpm. Compare this to a simple percentage-of-max approach: Zone 2 at 60–70% of 185 = 111–130 bpm — substantially lower, producing less training stimulus for the same effort level. The Karvonen formula is more accurate because it accounts for individual cardiovascular fitness reflected in resting heart rate.
The 30-minute field test for LTHR is the most practically accurate method for running-specific zone calculation. After a thorough warm-up, run as hard as you can sustain for 30 minutes on flat terrain. Your average heart rate over the final 20 minutes is your lactate threshold heart rate (LTHR). All five zones can be calculated as percentages of LTHR rather than max HR, which produces zones more specific to your running physiology. Repeat this test every 6–8 weeks as fitness changes.
Our running pace calculator can help determine pace-based training zones from recent race times — a useful complement to heart rate zones, particularly for interval sessions where heart rate response lags effort by 1–3 minutes. Our heart rate zone training guide covers the SportCoaching zone calculator and how to apply your zones across different training types.
The 80/20 Rule: What the Research Shows
The 80/20 training rule — 80% of training volume at low intensity (Zones 1–2), 20% at high intensity (Zones 4–5) — is not a coaching opinion. It emerged from Dr. Stephen Seiler’s systematic analysis of how elite endurance athletes actually train. In a foundational 2006 paper in the Scandinavian Journal of Medicine and Science in Sports, and a 2010 follow-up in the International Journal of Sports Physiology and Performance, Seiler documented that elite runners, cyclists, cross-country skiers, and rowers across all endurance disciplines follow remarkably similar intensity distributions — approximately 80% easy, 15–20% hard, and very little moderate effort.
The research outcome confirms the model works: a Journal of Sports Science study found runners following a polarised training model improved 11% more in 10K performance than those training at constant moderate intensity. Stoggl and Sperlich (2014) found well-trained runners achieved greater performance improvements with polarised compared to other training distribution models.
The reason the 80/20 model outperforms moderate-intensity-dominated training is the dual adaptation signal it generates. Zone 2 running drives aerobic base development (mitochondrial density, fat oxidation, cardiac efficiency) without generating significant fatigue. Zone 4–5 sessions drive lactate threshold and VO2max adaptations at intensities that Zone 3 cannot reach. Zone 3 produces neither benefit as effectively while accumulating substantial fatigue — meaning less recovery capacity for both the easy runs that build the base and the hard sessions that drive high-end adaptation.
Building volume safely at Zone 2 is covered in our guide on building mileage safely — the progressive increase in easy-running volume that creates the aerobic base that 80/20 training requires. The hard 20% is covered across our speed work guide, lactate threshold guide, and VO2 max workouts guide.
Running Zones by Race Distance
The optimal distribution of zone training shifts depending on the target race distance. All distances maintain the 80% easy foundation, but the composition of the hard 20% shifts toward the intensities most relevant to the event.
5K: The 5K is run at approximately Zone 5 effort — near VO2max. Zone 5 work (VO2max intervals: 400m–1000m at 5K pace) should constitute the primary quality session, representing 10–15% of weekly volume. Zone 4 threshold work supports lactate tolerance but is secondary. Our strides guide covers the short speed work that supplements Zone 5 intervals and is particularly important for 5K runners developing neuromuscular sharpness.
10K: The 10K is run at Zone 4–5 boundary effort. Zone 4 threshold sessions become the primary quality work (12–18% of weekly volume), with Zone 5 intervals for VO2max support. Threshold pace for a 10K runner is approximately 10K pace itself — so cruise intervals and longer tempo efforts are highly race-specific.
Half marathon: Half marathon pace sits in Zone 3–4. Zone 4 threshold work remains central, with some Zone 3 marathon-pace and longer tempo runs becoming more appropriate. 15–20% of weekly volume in Zone 3–4. Zone 5 work reduces in proportion.
Marathon: Marathon pace is Zone 2–3 for most runners (Zone 2 for well-trained runners, Zone 3 for beginners). The vast majority of training (75–80%) should be Zone 2 easy running building aerobic base and accumulated mileage. Threshold work (Zone 4) maintains lactate ceiling but volume is modest. Zone 5 is minimal.
Heart Rate vs Pace for Zone Training
Heart rate zones and pace zones are complementary tools, each with specific strengths. Heart rate reflects the body’s actual physiological workload — it adjusts for fatigue, heat, altitude, and daily stress automatically. If you’re dehydrated, stressed, or sleep-deprived, heart rate will be elevated for a given pace; using heart rate zones correctly means recognising this and slowing down rather than forcing the pace. The limitation is the 1–3 minute lag: heart rate doesn’t immediately reflect effort changes, making it less useful for short intervals where the effort changes every 30–90 seconds.
Pace zones are consistent on flat terrain in stable conditions and provide immediate feedback. They’re well-suited to structured track sessions, tempo runs, and any session where terrain is controlled. The limitation is that pace becomes unreliable on hills, trails, in wind, or in significant heat — conditions where heart rate zones are more accurate because they capture actual physiological load regardless of external variables.
Practical recommendation: use heart rate for easy runs, long runs, and any training in variable conditions (hills, heat, trails). Use pace for threshold and interval sessions on flat controlled surfaces where the lag in heart rate would require uncomfortable waiting before the metric becomes meaningful. The talk test is always available as a zone check requiring no technology — full comfortable conversation = Zone 2, short phrases = Zone 3, no conversation = Zone 4–5.
Apply Your Zones in a Complete Training Plan
SportCoaching's running training plans use zone-based structure to sequence easy, threshold, and interval sessions correctly through every training week — the right intensity at the right time, with the right recovery on either side.
FAQ: Running Zones
What are the 5 running zones?
Zone 1 (50–60% max HR): recovery. Zone 2 (60–70%): easy aerobic base — most training volume. Zone 3 (70–80%): comfortably hard, the “grey zone” — use sparingly. Zone 4 (80–90%): lactate threshold, tempo effort — primary quality training. Zone 5 (90–100%): VO2max and anaerobic intervals — hard quality sessions. Follow the 80/20 rule: 80% in Zones 1–2, 20% in Zones 4–5, minimal Zone 3.
How do I calculate my running heart rate zones?
The Karvonen formula using heart rate reserve is most accurate: HRR = max HR − resting HR; Zone HR = (HRR × %) + resting HR. The 30-minute field test gives your lactate threshold heart rate (LTHR) from which all zones can be calculated. Avoid the 220-minus-age formula — its ±10–12 bpm error produces meaningfully wrong zones for many runners.
What is the 80/20 running rule?
Spend 80% of weekly training volume in Zones 1–2 (easy, conversational) and 20% in Zones 4–5 (hard, threshold and VO2max). Minimal time in Zone 3. Based on Dr. Stephen Seiler’s research documenting elite endurance athlete training patterns. Studies show polarised training produces 11% greater 10K improvement than moderate-intensity-dominated training.
Why is Zone 3 called the grey zone in running?
Zone 3 is too hard to optimally build the aerobic base (Zone 2 does this better at lower fatigue cost) and not hard enough to drive lactate threshold or VO2max adaptation (Zones 4–5 do this). It accumulates real fatigue without a distinct enough adaptation signal to justify that fatigue. Runners who live in Zone 3 accumulate tiredness without producing the specific improvements that easy or hard training generates.
Should I use heart rate or pace for running zones?
Both. Heart rate for easy runs, long runs, and variable conditions (hills, heat, trails) — it captures actual physiological load. Pace for intervals and threshold sessions on flat controlled surfaces — heart rate lags 1–3 minutes behind effort changes, making it less useful for short intervals. The talk test works anywhere with no technology.
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