Understanding Energy Systems 

Introduction

Energy systems are the different ways the body produces energy depending on the intensity of the effort. Each type of effort relies on specific “substrates” (fats, carbohydrates, proteins) to meet its energy needs. Let’s explore how these systems work and how they connect to training intensity zones.

🟦 Lipolysis System (Low‑Intensity Zone)

Description: This is the low‑intensity system where the body draws from its fat stores to produce energy. It requires a constant supply of oxygen.

“Contrary to what many believe, weight loss doesn’t come from intense efforts, but from regular, moderate activity.”

Benefits:

• Optimal fat consumption

• Excellent for weight loss and building basic endurance

Examples: Brisk walking, easy‑pace cycling, yoga, gentle stretching.

Key idea: “Weight loss starts here.”

🟧 Glycolysis System (Moderate‑Intensity Zone)

Description: At a higher intensity, the body begins to rely mainly on carbohydrates for energy. Oxygen is still involved, but at a faster rate.

Benefits:

• Improves cardiorespiratory capacity

• Useful for moderate to sustained efforts

Examples: Jogging, swimming, moderate‑pace cycling.

Key idea: “This is where endurance is built.”

🟥 Anaerobic Lactic System (High‑Intensity Zone)

Description: Here, the body produces energy without oxygen, using carbohydrates exclusively. This leads to lactate accumulation, causing the familiar “burning” sensation.

Benefits:

• Develops power and speed

• Strengthens tolerance to intense efforts

Examples: Sprints, hill climbs, explosive exercises.

Key idea: “To get faster, this is the zone.”

🟪 Anaerobic Alactic System (Very High‑Intensity Zone)

Description: A system reserved for short, explosive efforts where the body uses ATP stored directly in the muscles, without producing lactate.

Benefits:

• Ideal for maximal performance over very short durations

Examples: Short sprints, weight lifting, explosive starts.

Key idea: “A system for very short but intense efforts.”

Conclusion

Understanding energy systems and intensity zones allows you to tailor your training to your goals, whether you want to lose weight, build endurance, or improve performance. So, get on your bike… and move at your own pace.

You’ll find a summary table showing the relationship between heart rate zones and energy systems in the Toolbox section.

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