top of page
Search

Zone 2 Training: Between Myth, Science and Meaningful Application

Writer: Alexander Eigner
Alexander Eigner
6 days ago
3 min read

Zone 2 training is often touted as the holy grail for fat burning and mitochondrial health – but what does science say? A detailed look at the benefits, limitations, and alternatives for recreational, competitive, and preventative exercise.



What is "Zone 2" training?


Zone 2 refers to a moderate exercise intensity below the first lactate threshold (LT1) – typically at a lactate level of 1.7–2.0 mmol/l. It is often around 60–70% of VO₂max and corresponds to a “relaxed but strenuous” long run where you can still talk (“Talk Test”).


In theory, Zone 2 should…

✅ Maximize fat burning ✅ Promote mitochondrial function ✅ Slow down aging processes ✅ Prevent metabolic diseases

But how much of this is established knowledge – and how much is fitness influencer marketing ?



🔍 The facts: What does the research show?

The recent review by Storoschuk et al. (2025) evaluated over 100 studies on the mitochondrial effects, fat burning, and fitness changes resulting from Zone 2 training. The result: mixed .


🧠 Mitochondria: Zone 2 is good – but not superior

🔬 Studies show that…

  • Zone 2 barely affects AMP/ADP metabolism

  • PGC-1α, the central biogenesis factor, is activated little or only during very long sessions (90–120 min).

  • Minimal protein changes occur after shorter sessions (< 60 min).


🔁 In comparison , high-intensity training (HIT) leads to significantly more efficient results:

  • stronger AMPK signal

  • higher PGC-1α activation

  • greater number and quality of mitochondria


Abbildung: Mythos vs. Realität, erstellt mit ChatGPT4o
Abbildung: Mythos vs. Realität, erstellt mit ChatGPT4o


🔥 Fat burning: Yes, but not exclusively


Zone 2 improves fat burning in untrained individuals – e.g., those who are overweight, have type 2 diabetes, or are obese. However:

  • Higher-intensity training methods also increase fat utilization.

  • Capillarization, IMTG storage and enzyme changes sometimes only occur at >50% VO₂max .

  • In trained individuals, Zone 2 is often too low to trigger additional adaptations.



🫀 Cardiovascular fitness (VO₂max): Higher intensity is crucial


💡 Perhaps the strongest indicator of longevity and health is cardiorespiratory fitness (CRF) – that is, your VO₂max.


🔹 Zone 2 training does not lead to an increase in VO₂max for many people.

🔹 In trained and healthy individuals, CRF only improves with more intensive training (e.g., from 75% VO₂max or interval training).

🔹 Studies show: The higher the intensity , the greater the improvement – even with the same training volume.



🎯 Practical implications: What does this mean for whom?


🧬 1. For health-conscious people (50+, prevention, “Healthy Agers”)

Goal: To preserve mitochondria, stabilize blood sugar, protect the heart


  • ✅ Zone 2 is a good entry point , low-threshold, low-risk

  • ⚠️ However, this alone is often not enough to substantially improve VO₂max or metabolic health.

  • 🏋️♂️ Ideally, supplement with moderate intervals (e.g., 4 x 4 minutes at 75–85% of maximum heart rate) and/or strength training.



🚴 2. For amateur athletes with little time

Goal: To improve fitness and maintain metabolic fitness.


  • 🚀 Interval training (HIT/MICT) is more time-efficient and effective for mitochondria and VO₂max

  • ✅ Zone 2 can be used as recovery training or for long, easy base training sessions.

  • ⏱ 2–3 intense sessions per week + 1–2 easy, long sessions → optimal



🏆 3. For competitive athletes:

Goal: Maximize endurance, periodize training


  • ✅ Zone 2 has clear justification : aerobic base block, fat metabolism training, mental relief

  • However, studies show that the extremely high mitochondrial density in professionals is not solely due to Zone 2 training – but rather to total training volume plus peak stimuli.

  • 🔁 A polarized model (e.g., 80% Zone 1–2 / 20% high-intensity) has been tested.


📚 Conclusion: Zone 2 is a tool – not a panacea.


✅ Yes: Zone 2 is pleasant, sensible and easy to implement

✅ Yes: It has positive metabolic effects – especially for beginners.

❌ No: It is not superior to higher-intensity training

❌ No: It is not enough on its own to achieve optimal mitochondrial, metabolic, and cardiac adaptations.


🧾 Literatur

Storoschuk, KL, Moran-MacDonald, A., Gibala, MJ, & Gurd, BJ (2025). Much Ado About Zone 2: A Narrative Review Assessing the Efficacy of Zone 2 Training for Improving Mitochondrial Capacity and Cardiorespiratory Fitness in the General Population . Sports Medicine, 55, 1611-1624. https://doi.org/10.1007/s40279-025-02261-y



 
 
 

Comments

bottom of page