Key Takeaways
- 80/20 Rule: Spend 80% of training time in Zone 1-2 for optimal endurance gains
- Heart rate zones are highly individual - use your actual max HR if known
- The Karvonen method (Heart Rate Reserve) is more accurate than % of max HR
- Power zones are the gold standard for cycling - they don't fluctuate like heart rate
- Pace zones work best for running on flat terrain in controlled conditions
What Are Training Zones?
Training zones are intensity ranges that help athletes structure their workouts for optimal performance gains. By training at specific intensities, you can target different physiological adaptations - from building aerobic base to improving anaerobic capacity and sprint power.
The concept was popularized by coaches like Joe Friel and Andrew Coggan, who developed systematic approaches to periodized training. Today, training zones are used by everyone from recreational runners to Olympic athletes.
Understanding Heart Rate Zones
Heart rate training zones divide your cardiovascular effort into distinct levels, each producing different training adaptations. The most accurate method uses your Heart Rate Reserve (HRR), also known as the Karvonen method.
Zone 1: Recovery (50-60% HRR)
Very easy effort for active recovery. Promotes blood flow without adding training stress. Used for warm-ups, cool-downs, and recovery days.
Zone 2: Aerobic Base (60-70% HRR)
Comfortable, conversational pace. Builds mitochondria, improves fat oxidation, and develops cardiovascular efficiency. The foundation of endurance training.
Zone 3: Tempo (70-80% HRR)
Moderate effort - can speak in short sentences. Improves muscular endurance and lactate clearance. Often called the "gray zone" - use sparingly.
Zone 4: Threshold (80-90% HRR)
Hard effort at or near lactate threshold. Improves your ability to sustain high intensities. Key zone for time trial and race performance.
Zone 5: VO2max (90-100% HRR)
Maximum sustainable effort for 3-8 minutes. Develops maximum aerobic capacity (VO2max). Used in interval training for peak fitness.
Pro Tip: Find Your True Max Heart Rate
The "220 minus age" formula is notoriously inaccurate (standard deviation of 10-12 bpm). For accurate zones, perform a field test: After a thorough warm-up, run 3 x 3 minutes at maximum sustainable effort with 2-minute recovery. Your highest reading in the final interval is close to your true max HR.
Running Pace Zones Explained
Pace zones, popularized by Jack Daniels' VDOT system, are based on your current race performance. They're particularly useful for running because pace is directly measurable and doesn't fluctuate with temperature, caffeine, or fatigue like heart rate does.
| Zone | Name | % of Race Pace | Purpose |
|---|---|---|---|
| E | Easy | 59-74% | Build base, recovery, long runs |
| M | Marathon | 79-88% | Race-specific marathon training |
| T | Threshold | 88-92% | Lactate threshold improvement |
| I | Interval | 98-100% | VO2max development |
| R | Repetition | 105-110% | Speed, running economy |
Cycling Power Zones
Power-based training is the most objective method for cycling because power output (measured in watts) is unaffected by external factors. The standard is the Coggan 7-Zone model based on your Functional Threshold Power (FTP).
What is FTP?
Functional Threshold Power is the highest power you can sustain for approximately one hour. It represents your lactate threshold - the intensity where lactate production and clearance are balanced. FTP is typically estimated using a 20-minute test multiplied by 0.95.
| Zone | Name | % of FTP | Duration |
|---|---|---|---|
| 1 | Active Recovery | <55% | Any |
| 2 | Endurance | 56-75% | 2-6+ hours |
| 3 | Tempo | 76-90% | 20-90 min |
| 4 | Lactate Threshold | 91-105% | 10-30 min |
| 5 | VO2max | 106-120% | 3-8 min |
| 6 | Anaerobic Capacity | 121-150% | 30s-2 min |
| 7 | Neuromuscular | >150% | <30s |
The Polarized Training Approach
Research shows elite endurance athletes spend approximately 80% of training time at low intensity (Zone 1-2) and 20% at high intensity (Zone 4-5), with minimal time in the "gray zone" (Zone 3). This polarized training approach maximizes adaptation while minimizing fatigue accumulation.
Pro Tip: Avoid the Gray Zone
Zone 3 is often called the "junk miles" zone. It's too hard to allow full recovery but too easy to drive significant adaptation. Most recreational athletes spend too much time here. Go easy enough on easy days (Zone 1-2) and hard enough on hard days (Zone 4-5).
How to Use Training Zones Effectively
Step 1: Establish Your Baseline
Perform appropriate tests for your sport: a max HR field test for running, an FTP test for cycling, or use a recent race result to calculate training paces.
Step 2: Structure Your Week
Plan your weekly training with the 80/20 principle in mind. Most sessions should be Zone 1-2, with 1-2 high-intensity sessions (Zone 4-5) per week.
Step 3: Monitor and Adjust
Use a heart rate monitor, power meter, or GPS watch to track your zones. Retest every 6-8 weeks as your fitness improves.
Frequently Asked Questions
Retest every 6-8 weeks during a training block, or whenever you notice workouts feeling significantly easier or harder than expected. Major fitness changes, illness, or long breaks should also prompt a retest.
Heart rate is affected by many factors: heat, humidity, caffeine, stress, sleep quality, and dehydration can all elevate HR. This is why power (for cycling) or pace (for running) can be more reliable metrics for structured training.
For heart rate, the Karvonen method (using Heart Rate Reserve) is most accurate because it accounts for your resting heart rate. For cycling, Coggan's 7-zone model is the industry standard. For running, Jack Daniels' VDOT-based pace zones are highly effective.
Yes! Swimming uses Critical Swim Speed (CSS) to establish pace zones, similar to FTP for cycling. CSS is calculated from your 400m and 200m time trial results and represents your threshold pace per 100m.
Zone 3 isn't inherently bad, but spending too much time there can lead to accumulated fatigue without proportional fitness gains. Some Zone 3 work (tempo/sweet spot) is valuable for building muscular endurance, but it shouldn't dominate your training.
Signs include: elevated resting heart rate, persistent fatigue, declining performance, mood changes, poor sleep, and increased illness frequency. If easy runs feel hard or hard workouts feel impossible, you may need more recovery time in Zone 1-2.