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How to Determine Your First Metabolic Threshold (Fatmax) | #26 ft. Dr. Robert Jacobs

Updated: Jan 31

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In this episode, Dr. Robert Jacobs and I discuss the concept of thresholds in exercise physiology and the ongoing debate surrounding their existence. We explore the importance of understanding and measuring first threshold, which marks the shift from maximal fat oxidation towards carbohydrate oxidation during exercise. We discuss the challenges of accurately measuring thresholds and the need for trend analysis over time. We also highlight the significance of Fatmax, the point at which the body maximizes fat oxidation, and its potential applications in performance and health.

This conversation explores the concept of Fatmax and its relationship to performance and fitness. We discuss the differences between Fatmax and other thresholds, such as ventilatory/gas exchange and lactate threshold. We also examine the impact of nutrition and training interventions on Fatmax. The conversation highlights the importance of low-intensity exercise and the confusion surrounding training zones. Various methods to measure lactate threshold and estimate the first threshold are discussed. As always we emphasize the principles of consistency, specificity, and progression in training. The benefits of Zone 2 training and the influence of exercise modality on intensity are also explored.


1) Thresholds in exercise physiology are points that mark shifts in metabolic processes and physiology during exercise.

2) The existence of thresholds has been a topic of debate, but they are valuable in identifying metabolic transitions and informing training.

3) Accurately measuring thresholds can be challenging, and trend analysis over time is crucial for understanding individual responses.

4) Fatmax occurs at a different percentage of VO2 max for each individual, and it can be influenced by nutrition and training interventions.

5) Low-intensity exercise is often neglected but plays a crucial role in improving efficiency and fat oxidation.

6) Different methods, such as lactate measurement and NIRS, can be used to estimate the first threshold.

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00:00 Introduction and Background

02:15 Thresholds and the Twitter Debate

08:21 Understanding First Threshold

13:24 Challenges in Measuring Thresholds

19:18 The Value of Thresholds in Training

25:43 The Importance of Trend Analysis

28:05 Different Methods to Measure First Threshold

36:39 The Significance of Fatmax

41:15 The Role of Oxygen in Thresholds

43:10 Considerations and Limitations of Fatmax

43:41 The Relationship Between Fatmax and Performance

44:25 The Difference Between Fatmax and Other Thresholds

45:31 The Consistency of Ventilatory Threshold

46:05 The Relationship Between Fitness and Fatmax

47:31 The Lack of Understanding of Fatmax

48:37 The Impact of Artificially Improving Fatmax

49:20 The Influence of Nutrition on Fatmax

50:09 The Neglected Importance of Low Intensity Exercise

51:08 The Confusion Around Training Zones

53:01 Different Methods to Measure Lactate Threshold

54:24 Using NIRS to Measure First Threshold

56:49 Estimating First Threshold Using the Talk Test

57:19 Estimating First Threshold Using Heart Rate Deviation

58:20 Estimating First Threshold Based on Exercise Intensity

59:45 The Importance of Consistency, Specificity, and Progression

01:01:34 The Benefits of Zone 2 Training

01:03:01 The Impact of Exercise Modality on Intensity

01:03:59 Closing Remarks and Call for Feedback

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