082 - Heavy Squats, Hard Thinking: How Load Impacts Brain Oxygenation
You’ve heard squats train the body, but what if they also train the brain? Recent research shows that loading protocols in the back squat don’t just affect muscle recruitment or metabolic stress—they change how your brain operates under the bar. This study used near-infrared spectroscopy (fNIRS) to assess how different rep ranges (3RM, 6RM, 10RM) affect prefrontal cortex (PFC) oxygenation.
The findings?
Heavy loads aren’t just physically demanding, they're neurologically potent.
For tactical professionals, this opens a new layer of programming insight: load selection doesn’t just sculpt strength, it shapes the central nervous system’s readiness, fatigue management, and potentially, cognitive sharpness under stress.
What They Found:
Eighteen resistance-trained men (average age ~28 years) completed back squat sets to failure at 3RM, 6RM, and 10RM. Using fNIRS, researchers tracked changes in cerebral oxygenation: oxygenated hemoglobin (HbO2), deoxygenated hemoglobin (HHb), total hemoglobin (tHb), and the tissue oxygenation index (TOI).
3RM produced the greatest increase in HbO2 and tHb, indicating heightened cerebral blood flow and oxygenation.
10RM produced smaller, delayed changes, especially in HHb, which only shifted significantly by the final rep.
TOI increased most under 3RM, moderately under 6RM, and not at all under 10RM.
These patterns suggest heavy loads drive more intense and earlier engagement of the prefrontal cortex, the area responsible for motor control, decision-making, and exercise tolerance.
Interestingly, blood oxygenation in the muscle and the brain didn’t move in lockstep. While muscular effort increased across all rep schemes, the neurological cost scaled sharply with load intensity, pointing to a separation between physical work and central demand.
What This Means:
Your brain’s oxygen profile may be the limiting factor, not your quads. That’s not poetic, it’s literal. Heavy squatting (3RM) forces early and sustained prefrontal engagement. This implies greater cognitive strain, motor coordination demand, and executive control activation.
For tactical athletes, whose real-world tasks combine strength, stress, and complex decision-making, this is critical. Programming with 3RM efforts could have carryover not just to raw force production, but to mental resilience and neuroplasticity, especially when timed and recovered appropriately.
By contrast, 10RM protocols may yield greater peripheral adaptations with less central fatigue, making them useful for volume accumulation and hypertrophy phases, but with lower neurological toll.
Tactical Implications:
Train the brain under the bar: Heavy squats don’t just test your legs—they condition your central command system.
Balance high-CNS load with cognitive tasks: Pair 3RM protocols with situational decision-making drills for integrated adaptation.
Don’t overload the system back-to-back: High-load CNS sessions (e.g., 3RM squats) demand longer recovery. Plan your week accordingly.
Use 10RM when you want reps, not neural strain: Great for volume and muscle growth phases without frying the brain.
Recognize neural fatigue in your athletes: If your team is sluggish on tactical drills post-heavy lifts, you’re seeing real PFC fatigue.
Questions To Consider:
Are your high-load training sessions building central readiness, or just crushing recovery?
How are you periodizing CNS vs. peripheral loading throughout your week?
Could your athlete’s missed lift or sloppy rep be a brain oxygenation issue, not a muscle one?
Should we monitor PFC activation as closely as we track bar speed and heart rate?
What would your training look like if you treated the brain as a primary target, not an afterthought?
Leitão L, Pareja-Blanco F, Marinho D, Neiva H. Effects of Different Back Squat Protocols on Prefrontal Cortex Oxygenation Responses. J Strength Cond Res. 2025;39(8):845-849. Published 2025 May 16. doi:10.1519/JSC.0000000000005141