03/31/2025
WHY HIIT ISN’T ALWAYS IT: 🤔 Why More Isn’t Better, and What the Science Really Says 🧬
High-Intensity Interval Training (HIIT) is everywhere—marketed as the fastest way to get fit, burn fat, and boost performance. But here’s the problem: when HIIT is overused, misapplied, or promoted by unqualified influencers, it can do more harm than good. 😅
At Fit Physical Therapy, we’re all about getting people stronger, healthier, and more capable… for life! So here’s a breakdown of why too much HIIT may actually be breaking you down instead of building you up. 🥴
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What Is Anti-HIIT?
“Anti-HIIT” isn’t about avoiding intensity altogether—it’s about understanding the risks of doing it too often and ignoring what your body really needs to thrive. The science tells us that the problems with too much HIIT:
1. Mitochondrial Damage & Dysfunction
• Your mitochondria (the cell’s energy producers) can become impaired with repeated high-intensity sessions.
• Studies show that low-to-moderate steady-state training is better at improving mitochondrial function and overall energy efficiency.
• Overuse of HIIT has been linked to reduced insulin sensitivity and impaired metabolism in just weeks [Flockhart et al., Cell Metabolism, 2021].
2. Hormonal Disruption (Cortisol Overload)
• HIIT spikes cortisol and adrenaline—fine in small doses, harmful when chronically elevated.
• Over time, this can lead to burnout, poor sleep, immune suppression, and even muscle loss [Healthline, 2021; Maffetone, 2018].
3. Higher Risk of Injury
• A Rutgers study found HIIT to be associated with increased risk of knee, shoulder, and tendon injuries—especially when done unsupervised or with poor form.
• Youth athletes are especially vulnerable due to underdeveloped movement patterns and recovery systems.
4. Recovery Bottlenecks
• HIIT isn’t “easy to recover from just because it’s short.” Your nervous system, joints, and energy systems may take days to fully bounce back.
• Without enough recovery, you plateau—or regress.
5. Aerobic Base Erosion
• Chronic HIIT neglects your aerobic engine—the system responsible for endurance, fat metabolism, and overall health.
• Without low-intensity training, you’re training in the “black hole zone”—too hard to recover, not hard enough to adapt.
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What the Research Shows:
• Flockhart et al. (2021): Chronic HIIT impaired mitochondrial function and glucose tolerance in healthy individuals.
• Laursen & Jenkins (2002): HIIT improves VO₂max but is less efficient than aerobic training for mitochondria.
• Maffetone Method: Promotes fat burning, reduces inflammation, and improves health markers better with low-intensity training.
• StrongFirst A+A Protocol: Uses alactic power (short, explosive bursts) with aerobic recovery—no lactic acid overload, just performance and longevity.
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So What Should You Do Instead?
Train Smarter:
• 2–3 HIIT sessions per week is plenty for most people.
• Build your base with Zone 2 training (brisk walking, light cycling, nasal-breathing cardio).
• Practice the A+A method (short bursts, long rests).
• Listen to your body: Progress is built on recovery.
• If you’re tired, inflamed, or feeling worse after workouts—not better—it’s time to reassess.
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Why This Matters:
We’re seeing more people in our clinics and gym burnt out from doing too much high-intensity training, thinking that pain and exhaustion are signs of progress. They’re not.
We’re also seeing fitness content online from non-health professionals pushing “everyday HIIT” programs that ignore the science. These often lack proper progressions, recovery, or individualized plans—especially dangerous for beginners, older adults, and youth athletes.
Our job isn’t to tell you what to do. It’s to educate you, so you can make informed decisions based on real evidence, not trends.
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Sources (Check them to Research Yourself):
• Flockhart et al., Cell Metabolism (2021) – Excess HIIT causes mitochondrial dysfunction
• Laursen & Jenkins (2002) – Recovery is critical for HIIT adaptations
• Maffetone, P. – The Maffetone Method, “HIIT can impair aerobic base”
• StrongFirst – A+A Training: Power Without the Waste
• Rutgers University – HIIT and increased injury risk
• Healthline (2021) – Cortisol and overtraining symptoms
• Youth Fitness Guidelines (Amac Training) – HIIT risks in kids and teens
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You don’t need to be wrecked to get results.
Train strong. Train smart. Build for the long game.
If you have questions or want help structuring your training around strength, performance, and long-term health, we’re here to help.
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Fit Physical Therapy LTD
Strength. Movement. Recovery.