🩺 Health & WellnessLast updated March 14, 2026

Fitness & Exercise Guide: Workout Planning, Calories Burned & Heart Rate Zones

Train smarter, recover better — science-backed fitness fundamentals

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4+

Calculators

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30-40%

Mortality ↓

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8 min

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Key Takeaways

Calories burned = MET value × body weight (kg) × duration (hours). Walking (3.5 METs) vs. running (9.8 METs) shows why intensity matters.
Heart rate zones: Zone 2 (60–70% max HR) builds aerobic base; Zone 4 (80–90% max HR) improves VO2max.
Max heart rate estimate: 220 − age (simple) or 208 − 0.7 × age (Tanaka formula, more accurate for adults).
Progressive overload — gradually increasing weight, reps, or volume — is the #1 driver of strength and muscle gains.
Recovery is when adaptation happens: 48–72 hours between training the same muscle group, 7–9 hours of sleep per night.

Exercise is the most powerful health intervention available — reducing all-cause mortality by 30–40% in active adults according to the WHO physical activity guidelines. But the difference between effective training and wasted effort comes down to understanding intensity, volume, and recovery. This guide covers the science of exercise energy expenditure, heart rate training zones, workout programming, and free tools like the calories burned calculator and heart rate calculator to plan it all.

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The Science of Exercise Calorie Burn

Exercise calorie expenditure is calculated using MET values (Metabolic Equivalents of Task). One MET = 3.5 mL O₂/kg/min, roughly 1 kcal/kg/hour. Formula: Calories = MET × weight (kg) × duration (hours). Walking at 3 mph = 3.5 METs. Running at 6 mph = 9.8 METs. Swimming laps = 8 METs. Strength training = 3–6 METs depending on intensity. The afterburn effect (EPOC) adds 6–15% more calories for high-intensity exercise over the following 24 hours. Use our calories burned calculator with 100+ activities, or check MET values in the Compendium of Physical Activities.

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Heart Rate Training Zones Explained

Training zones are percentages of your maximum heart rate (MHR). Zone 2 (60–70% MHR) is where aerobic base fitness is built — the "conversational pace" zone. It should comprise 80% of your weekly training volume. Zone 4 (80–90% MHR) trains your anaerobic threshold and improves VO2max — do this 1–2 sessions per week via intervals. Zone 5 (90–100%) is maximum effort for sprint training, used sparingly. The polarized training model (80% easy / 20% hard) is used by elite athletes — see ACSM (American College of Sports Medicine) guidelines. Find your zones with our heart rate calculator.

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Workout Programming Fundamentals

Effective training follows three principles: progressive overload (gradually increase stress), specificity (train the adaptation you want), and recovery (growth happens during rest). A balanced weekly plan: 3 resistance sessions (push/pull/legs or upper/lower split), 2–3 cardio sessions (mostly Zone 2 with one interval session), and 1–2 rest or active recovery days. The CDC physical activity guidelines recommend 150+ minutes of moderate activity per week. Generate a custom plan with our workout generator and estimate your daily energy needs with the BMR calculator.

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Recovery, Sleep & Adaptation

Muscles need 48–72 hours to recover and grow stronger after resistance training. Sleep is the most powerful recovery tool: 7–9 hours per night is optimal, with growth hormone peaks during deep sleep (stages 3–4). Signs of overtraining: elevated resting heart rate, decreased performance, persistent fatigue, and increased injury frequency. Deload weeks (50% volume reduction every 4–6 weeks) prevent plateaus and reduce injury risk. Monitor your resting heart rate trends with our heart rate calculator.

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Related Tools & Calculators

4 free tools linked to this guide

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Calories Burned Calculator

Calculate calories burned for 100+ activities by body weight and duration.

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Heart Rate Calculator

Find your max heart rate and optimal training zones for any fitness goal.

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Workout Generator

Generate a personalized workout routine based on your goals and equipment.

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BMR Calculator

Calculate your baseline calorie burn to understand total daily expenditure.

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Frequently Asked Questions

How many calories does exercise burn?

It depends on the activity, your body weight, and duration. Use the MET (Metabolic Equivalent of Task) formula: Calories = MET × weight (kg) × hours. Examples at 70kg: walking (3.5 METs) burns ~245 cal/hour, jogging (7 METs) burns ~490 cal/hour, cycling (8 METs) burns ~560 cal/hour.

What are heart rate training zones?

Zone 1 (50–60% max HR): recovery/warm-up. Zone 2 (60–70%): fat burning & aerobic base. Zone 3 (70–80%): aerobic endurance. Zone 4 (80–90%): anaerobic threshold & VO2max. Zone 5 (90–100%): maximum effort, short bursts only. Most health benefits come from spending 150+ minutes/week in Zones 2–3.

How do I calculate my maximum heart rate?

The simplest formula is 220 − age. The more accurate Tanaka formula is 208 − (0.7 × age). For a 35-year-old: 220 − 35 = 185 bpm (simple) or 208 − 24.5 = 183.5 bpm (Tanaka). These are estimates — a graded exercise test provides the true max.

How often should I exercise per week?

The WHO recommends 150–300 minutes of moderate-intensity or 75–150 minutes of vigorous-intensity aerobic exercise per week, plus strength training 2+ days per week. For most people, 4–5 sessions combining cardio and resistance training is optimal.

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