By Dr. Steven Long, DO, MHA, CPT
Beyond Health | Precision Medicine for High-Performance Living
Exercise isn’t just “easy” or “hard.” Your body responds very differently depending on the intensity of your effort—and those responses determine which energy systems you’re using, what adaptations you’re building, and which health outcomes you’re targeting. This is where exercise zones come in. Understanding them helps you train smarter, avoid burnout, and align your workouts with your long-term goals.
The Five Common Training Zones
Exercise zones are typically based on a percentage of your maximum heart rate (HRmax) or, more precisely, your lactate threshold and ventilatory threshold.
A rough HRmax estimate:
HRmax ≈ 220 – age
(Not perfect, but a reasonable starting point for most people.)
Zone 1: Recovery / Easy
- Intensity: 50–60% HRmax
- How it feels: Very light, easy conversation pace
- Fuel source: Primarily fat oxidation (lipolysis) with low muscle glycogen use
- Benefits:
- Improves basic aerobic efficiency
- Supports recovery between harder sessions
- Reduces stress on joints and nervous system
Zone 2: Aerobic Base
- Intensity: 60–70% HRmax
- How it feels: Comfortable, able to speak in full sentences; breathing is deeper but not labored
- Fuel source: Predominantly fat oxidation, with gradual increase in carbohydrate use as intensity rises
- Benefits:
- Expands mitochondrial density and efficiency
- Improves metabolic flexibility (ability to use fat or glucose as fuel)
- Strongly associated with longevity and lower risk of metabolic disease
- Builds the foundation for higher-intensity work
- Evidence: Seiler et al. (2010) showed elite endurance athletes spend ~80% of training at low intensity (Zones 1–2) to maximize long-term performance gains.
Zone 3: Tempo / Moderate
- Intensity: 70–80% HRmax
- How it feels: “Comfortably hard,” speaking is possible but broken into short phrases
- Fuel source: Increased glycogenolysis alongside fat oxidation
- Benefits:
- Improves muscular endurance
- Increases lactate clearance efficiency
- Bridges the gap between base aerobic work and high-intensity sessions
Zone 4: Threshold
- Intensity: 80–90% HRmax
- How it feels: Hard; conversation is limited to single words
- Fuel source: Predominantly glycogenolysis, with lactate production and clearance near maximum sustainable level
- Benefits:
- Improves lactate threshold
- Enhances performance in sustained hard efforts
- Strong VO2 max stimulus
Zone 5: VO2 Max / Anaerobic
- Intensity: 90–100% HRmax
- How it feels: Very hard; speaking is nearly impossible; short bursts of effort
- Fuel source: Almost exclusively glycogenolysis and anaerobic glycolysis; rapid lactate accumulation
- Benefits:
- Maximizes VO2 max
- Increases cardiac output (stroke volume)
- Boosts anaerobic capacity and neuromuscular recruitment
How to Measure or Recognize Your Zone
- Heart Rate Monitoring
- Most accessible method (smartwatch, chest strap)
- Start with HRmax calculation, then adjust based on your perceived exertion and progress
- Talk Test
- Zone 2: Full sentences
- Zone 3: Short phrases
- Zone 4+: Single words
- Lactate or Gas Exchange Testing
- Gold standard for serious athletes, performed in lab settings
- Identifies ventilatory and lactate thresholds precisely
Practical Application at Beyond Health
- Zone 2: 2–3 sessions/week (30–60 minutes) for aerobic base, metabolic health, fat oxidation
- Zone 4–5: 1–2 sessions/week (intervals or threshold work) for VO2 max and performance
- Strength training: 2–3 sessions/week to complement aerobic work and support longevity
This approach builds cardiovascular health, muscular strength, metabolic flexibility, and resilience without overtraining.
Bottom Line
Different exercise zones target different adaptations. While Zone 2 is foundational for health and longevity, higher-intensity zones are valuable for performance and VO2 max. But the ultimate goal is not to live in one zone or obsess over numbers—it’s to build a balanced, sustainable training habit that keeps you strong, metabolically healthy, and injury-free for decades.
