12💪Gym
High Intensity Interval Training
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Action Protocol
Perform 30–60s all-out sprints until HR >90%, then active rest until heart rate drops to 120bpm
Evidence Gallery
In Depth Protocol
- The Metabolic Hack (Mitochondrial Density): Unlike steady-state cardio, HIIT stresses the cell's energy demand so severely that it triggers Mitochondrial Biogenesis (growing more power plants in the cell). Research shows Sprint Interval Training is ~2-3x more efficient at boosting mitochondrial content per hour than standard endurance training.
- The Afterburn (EPOC): The oxygen debt created during high-intensity intervals forces the body into Excess Post-Exercise Oxygen Consumption (EPOC). This elevates your metabolic rate for hours after finishing as the body works to restore homeostasis.
- The Neuro-Hack (BDNF): High-intensity bursts (above the lactate threshold) force muscles to produce Lactate. This lactate triggers the release of Brain-Derived Neurotrophic Factor (BDNF), which helps grow new neural pathways (Neuroplasticity) and improves memory retention.
✅ Pros
- Hormonal Response: Increase Growth Hormone (GH) and Free Testosterone levels.
- VO2 Max Efficiency: Delivers superior improvements in VO2 Max (~12% gain) vs steady state cardio
- Neuroplasticity: Increases BDNF, protecting against cognitive decline and enhancing learning speed.
⚠️ Cons
- CNS Fatigue: Highly taxing on the Central Nervous System; requires longer recovery than Zone 2 cardio.
Sources & Verification
Reviewed by Tomas|Last updated: 1/7/2026