Target Heart Rate for Cardio — 5 Training Zones

The 5-Zone Heart Rate Model Explained

• Zone 1 — Recovery (50-60% max HR): Very light effort. Use for warm-ups, cool-downs, and active recovery between hard sessions. Promotes blood flow without stress. Example: easy walking or cycling.
• Zone 2 — Endurance (60-70% max HR): Light-to-moderate effort where conversation is still comfortable. Builds aerobic base, improves fat metabolism, and forms the foundation of all endurance training. Most training volume should live here.
• Zone 3 — Tempo (70-80% max HR): Moderately hard effort. Raises lactate threshold and improves cardiovascular efficiency. Conversation becomes difficult but short phrases remain possible. Good for race-pace preparation at half marathon or longer distances.
• Zone 4 — Threshold (80-90% max HR): Hard effort approaching lactate threshold. Raises VO2 max, improves lactate clearance, and builds race-specific speed endurance. Typically unsustainable beyond 20-40 minutes.
• Zone 5 — VO2 Max (90-100% max HR): Maximum effort. Short intervals of 1-5 minutes push maximal oxygen uptake and top-end speed. Requires significant recovery between efforts and sessions. Use sparingly, 1-2 sessions per week.

Training Distribution by Goal

Endurance athletes following the 80/20 rule spend approximately 80% of total training time in Zones 1-2 and 20% in Zones 3-5. This distribution, supported by sports science research including Maffetone's low-heart-rate training and Seiler's polarized training model, produces the best balance of aerobic development and performance improvement. For general fitness and weight loss, a 90/10 split (90% Zones 1-2, 10% Zone 4+) is even more effective and reduces injury risk. Competitive runners and triathletes may shift to 70/30 during peak training blocks, with structured interval and threshold sessions in Zones 4-5. Use the HealthCalc Target Heart Rate Calculator to set zone boundaries precisely for your age and resting heart rate.

Session Length by Zone

• Zone 1 sessions: 15-30 minutes. Use for warm-ups before harder work, cool-downs after workouts, or dedicated recovery days between high-intensity sessions.
• Zone 2 sessions: 45-90 minutes. The sweet spot for building aerobic endurance and burning calories. Can be sustained comfortably and forms the bulk of a weekly training plan.
• Zone 3 sessions: 20-45 minutes. Tempo runs and threshold rides improve lactate clearance without the extreme fatigue of Zones 4-5. One session per week is sufficient for most athletes.
• Zone 4 sessions: 10-30 minutes of continuous work or accumulated intervals. Typical format: 2×20 min at threshold or 4×5 min at threshold with 2-min recovery.
• Zone 5 sessions: 1-8 minutes of accumulated effort. Typical format: 6-10 × 1 min intervals at VO2 max with equal recovery, or 3-4 × 3 min at VO2 max with 3-min recovery.

Monitoring Your Zone Training

A heart rate monitor — chest strap or optical wrist sensor — provides real-time feedback essential for zone-based training. Chest straps are more accurate during high-intensity interval training where wrist optical sensors may lag by 3-5 bpm. Pair your heart rate data with perceived exertion on the Borg scale (1-10) to cross-check that your heart rate zones feel correct. If Zone 3 feels easy enough to hold a conversation, your zones may be set too high. If Zone 2 feels breathless within 10 minutes, your zones may be set too low. Reassess your max heart rate annually, as it naturally declines by approximately 1 bpm per year of aging.