In the modern era of "high-intensity interval training" (HIIT) and "no pain, no gain" fitness culture, the suggestion to slow down is often met with scepticism. However, if we look at the gold standard of exercise physiology, the evidence is clear: to run fast, we must first master the art of running slowly.
Today, I want to take a deep dive into a seminal paper that forms a cornerstone of my coaching philosophy: "Maximum Aerobic Function: Method for Determining Aerobic Fitness in the Resistance Era" by Dr Phil Maffetone and Prof. Paul Laursen (2016).
The "Resistance Era": Why We Are Over-Training
The authors begin by identifying a modern crisis in fitness. We live in an "over-fat" and "over-stressed" society, yet our approach to exercise is often to add more stress. Maffetone and Laursen argue that many athletes are stuck in a cycle of "anaerobic over-dependence."
By training too hard, too often, runners develop a "sugar-burning" metabolism that leads to:
Frequent Injuries: High-intensity training puts immense mechanical stress on joints and tendons.
Systemic Inflammation: Constant "red-lining" prevents the body from recovering fully.
Plateaued Performance: Without a solid aerobic base, your top-end speed has no foundation to sit upon.
What is Maximum Aerobic Function (MAF)?
The MAF method is designed to identify the highest heart rate at which you can exercise while remaining almost entirely aerobic. This is the point where your body is most efficient at oxidising fat for fuel rather than relying on limited glycogen (sugar) stores.
The 180-Formula
The paper details the famous 180-Formula, which I use as a primary guideline for my athletes. By subtracting your age from 180 (and adjusting for health and injury history), you find your MAF HR.
Example: A 40-year-old runner with a solid health history has a MAF limit of 140 bpm.
For many, this number feels "too slow." You might find yourself walking on hills or being overtaken by joggers in the park. But as Maffetone and Laursen explain, staying below this ceiling is the only way to specifically stimulate the development of your slow-twitch muscle fibres and mitochondrial density.
Key Findings: Why Fat-Adaptation Matters
The 2016 paper highlights three critical benefits of prioritising your Maximum Aerobic Function:
1. Metabolic Flexibility
Humans evolved to be "fat-burning beasts." Our fat stores are virtually unlimited, even in lean athletes. By training at MAF, you teach your body to utilise fat as its primary energy source. This "spares" your glycogen for the end of a race, effectively making you "bonk-proof."
2. Autonomic Balance
High-intensity training triggers the "fight or flight" (sympathetic) nervous system. If we spend too much time here, we experience elevated cortisol and poor sleep. MAF training promotes "parasympathetic" dominance—the state of rest, repair, and recovery. This is why many of my athletes find they feel more energised after a MAF run than before they started.
3. Structural Integrity
By slowing down, your gait becomes more natural and less "forced." This allows the connective tissues in your feet and ankles to strengthen without being overwhelmed by the high impact of anaerobic sprinting.
The "MAF Test": Measuring Progress
One of the most practical takeaways from the research is the MAF Test. Because you are training at a fixed heart rate (e.g., 140 bpm), the only variable that can change is your pace.
Month 1: You run 10:00 min/mile at 140 bpm.
Month 4: You run 8:30 min/mile at 140 bpm.
This is the "holy grail" of running: running faster for the same amount of internal effort. The science shows that as your aerobic engine grows, your "aerobic floor" rises, eventually pushing your anaerobic "ceiling" higher without you ever having to do a single gut-busting interval.
My Coaching Perspective
As someone who has transitioned from a background of obesity and physical impairment to running sub-17:30 parkruns, I can personally vouch for this research. I didn't get faster by running harder; I got faster by building a massive aerobic engine that allowed me to recover from the occasional hard session with ease.
If you are a "serious but slower" runner looking to break through a plateau, the answer isn't "more effort." The answer is more efficiency.
Ready to Find Your MAF?
If you’re interested in applying the Maffetone and Laursen research to your own training, I am currently offering a few free portfolio coaching spots to help athletes establish their base phase.
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