What Is Zone 2?

Zone 2 refers to steady, low-intensity aerobic work performed below your first threshold—also called the aerobic threshold (LT1) or ventilatory threshold 1 (VT1). In this zone, you predominantly burn fat, produce manageable amounts of lactate, and can sustain the effort for long durations.

Practical markers of Zone 2:

• Breathing is calm; you can hold full, comfortable conversations.
• Perceived effort feels easy to steady (RPE 2–3 out of 10).
• Heart rate is moderate and stable with minimal drift over time.

Rule of thumb ranges (individual variation is large):

• Heart rate: roughly 60–75% of HRmax, or 65–80% of heart rate at lactate threshold (LT2). Prefer personal testing over formulas.
• Cycling power: ~56–75% of FTP (Coggan Zone 2), then refine using breathing and HR stability.
• Running pace: an “easy” conversational pace; you should be able to nasal-breathe or talk in full sentences.

Why Zone 2 Works (The Physiology)

• Mitochondrial biogenesis: Builds more and bigger mitochondria, improving your ability to produce aerobic energy.
• Fat oxidation: Increases the rate and power at which you can use fat for fuel, sparing glycogen for when you need it.
• Capillarization: Expands the network of tiny blood vessels, improving oxygen delivery and waste removal.
• Lactate clearance: Upregulates transporters (e.g., MCT1) and enzymes that recycle lactate as fuel.
• Autonomic balance: Encourages parasympathetic tone, aiding recovery and lowering resting heart rate.
• Low mechanical stress: Enables high training volume with lower injury risk vs constant hard efforts.

Bottom line: Zone 2 builds the aerobic “engine” that supports higher intensities, better endurance, and improved health (metabolic flexibility, insulin sensitivity, and blood pressure).

How to Find Your Personal Zone 2

Best: Threshold Testing

• Lab testing: Lactate or ventilatory assessments identify LT1/VT1 precisely.
• Field testing (lactate meter): Long, steady efforts; Zone 2 typically aligns with blood lactate ~1.5–2.0 mmol/L for many athletes.

Practical Field Methods (No Lab Required)

• Talk test: You can speak in full sentences without gasping. If sentences feel choppy, you’re likely above LT1.
• Breathing: Calm, mostly nasal breathing is often sustainable in Zone 2.
• Heart-rate stability: On a 45–90 minute steady effort, HR should rise slightly during warm-up, then stay stable with low decoupling (pace/power stays the same while HR doesn’t creep up >5–7%).
• RPE: Feels easy, “could do this for hours” (2–3/10).

Quick Estimates (Start Here, Then Refine)

• Heart rate: Start around 60–70% of HRmax for beginners; experienced athletes may sit closer to 70–75% of HRmax. Adjust to keep breathing conversational and HR stable.
• Cycling power: 56–70% of FTP to start; adjust using breathing/HR drift.
• Running pace: Very easy. Expect it to be significantly slower than your race paces—this is normal and desirable.

Note on formulas: Age-based HR formulas (e.g., 220 − age) have large individual errors. Treat them as a starting guess only.

How Much Zone 2 Should You Do?

• Distribution: Many benefit from a polarized or pyramidal approach:

  • Polarized: ~80–90% low intensity (Zone 2 and below), 10–20% high intensity.
  • Pyramidal: ~70% low, ~20% moderate, ~10% high.

• Weekly volume:

  • Minimum effective: 2–3 hours/week for noticeable gains.
  • Good progress: 4–6 hours/week.
  • Advanced: 6–12+ hours/week, scaled gradually and sensibly.

• Session length: 30–120 minutes common. Long rides/runs can extend 2–5 hours for experienced athletes.

Sample Zone 2 Workouts

• Runner (45–60 min): 10–15 min warm-up easy jog, 25–35 min steady Zone 2, 5–10 min cool-down. Optional 4–6 × 10–20 sec relaxed strides after.
• Cyclist (90 min): 10–15 min warm-up, 60–70 min steady Zone 2 on mostly flat terrain or steady trainer power, 5–10 min cool-down.
• Triathlete (brick): 60–90 min Zone 2 ride + 15–20 min easy run, both conversational.
• Rowing/Erg (45 min): 10 min warm-up, 25 min Zone 2 steady, 10 min cool-down.
• Swim (45 min): 300–500m easy warm-up, 3–4 × 8–10 min continuous Zone 2 with 1 min easy between, 200m cool-down.

Building a Week (Examples)

• Time-crunched (4–5 hrs total):

  • Mon: Rest or mobility
  • Tue: 45–60 min Zone 2
  • Thu: 45–60 min Zone 2
  • Sat: 90–120 min Zone 2 long session
  • Sun: Optional 30–45 min easy or short intervals (e.g., 6 × 2 min hard) if recovered

• Intermediate (6–8 hrs):

  • 2–3 midweek Zone 2 sessions (45–75 min)
  • 1 long Zone 2 session (2–3+ hrs)
  • 1 short high-intensity session (20–40 min of total work)
  • 1 strength session (30–45 min)

Progress by adding 5–15% volume every 1–3 weeks, then take a lighter week.

How to Know It’s Working

• More pace/power at the same heart rate.
• Reduced decoupling: After 60–90 minutes, power/pace stays steady without HR creeping up >5%.
• Lower resting heart rate and improved HRV (if you track it).
• Lower lactate at a given pace/power (if you measure).
• Faster recovery and ability to handle more training.

Fueling and Recovery

• Fueling:

  • Up to ~60–90 minutes: water/electrolytes may suffice if starting well-fed.
  • Longer sessions: 20–40 g carbs per hour (or more for cyclists), plus electrolytes.
  • Fasted Zone 2 can improve fat use for some, but consider performance goals and total load. Don’t fast long/hard sessions or if it impairs recovery.

• Hydration: Aim for steady fluid intake, adjust for heat/humidity.
• Recovery: Sleep, protein (0.3 g/kg within a few hours), and easy days. Zone 2 is gentle, but volume still adds stress.

Common Mistakes

• Going too hard: If you can’t speak comfortably or HR drifts up steadily, back off.
• Chasing pace on hills: Use effort/HR/power to stay in Zone 2; let pace slow uphill.
• Using generic formulas as gospel: They’re starting points—refine with breathing and drift.
• Neglecting intensity entirely: A small dose of high-intensity sharpens fitness.
• Under-fueling long sessions: Low energy compromises quality and recovery.
• Poor device data: Optical wrist HR can be noisy; chest straps are often more reliable.

Special Considerations

• Beginners: Walking can be excellent Zone 2. Consistency matters more than speed.
• Masters athletes: Recovery takes longer; keep most training easy and be patient with progression.
• High heat/altitude: HR rises at the same pace—follow HR/breathing, not pace.
• Medications (e.g., beta-blockers): HR-based zones may not apply; use RPE and talk test.
• Strength training: 1–2 sessions/week pairs well with Zone 2 for durability and performance.

Quick FAQ

• How long until I see results? Many notice improvements in 4–8 weeks; larger changes accrue over months.
• Can I do Zone 2 every day? Often yes if duration is sensible. Listen to fatigue and rotate lighter days.
• Is walking/hiking Zone 2? Yes, if it meets the breathing/HR/RPE criteria.
• Do I need a lactate meter? No. Helpful for precision, but talk test + HR drift works for most.
• What about “junk miles”? True Zone 2 is not junk—it’s the foundation that enables more high-quality training.

Putting It All Together

Zone 2 is simple: move steadily, breathe easily, and stay consistent. Use conversational breathing and stable heart rate to guide intensity, build up your weekly volume gradually, and add a small amount of high-intensity work when recovered. Over time, you’ll go farther and faster at the same easy effort—proof that the low-intensity secret is working.

Disclaimer: This article is educational and not medical advice. If you have cardiovascular or metabolic conditions, consult a healthcare professional before changing your exercise routine.