Heart Rate Training: The Highest Heart Rate is Not The Goal

Including a 12 week base training block to get you started

Most people train at the wrong intensity. Not because they’re lazy, but because the industry taught them to chase the wrong target. Heart rate has become a performance badge — higher means harder, harder means better, and “better” means you worked. That is the story people are sold. Even Peloton highlights your highest heart rate as your best ride. Influencers push red-zone sweat as a virtue. Fitness culture rewards exhaustion over adaptation.

We are also programmed, and perhaps we programmed ourselves, to think that if we are not sweating or breathing hard, we are not doing anything important.

This is all wrong. Let’s get into this.

The average runner runs too fast on their slow days and too slow on their fast days.

Pounding a high heart rate (HR) every day is not training. It’s stress. Not that stress is bad. The context matters. Let’s explore this further.

Heart rate is not really the goal. What matters is which physiological response is triggered at that heart rate. In each heart rate zone, the metabolic machinery in our cells is doing something different regarding energy partitioning- or what fuel(s) we use to create energy to power our efforts. What’s taking place in the cell matters and determines which zone we are in.

The zone dictates the adaptation… and the status or health of our mitochondrial density, lactate clearance ability, capillary growth, fat oxidation, stroke volume, and autonomic balance all play a role in determining how long we can stay in that zone and what the benefits will be. You don’t get healthier by hitting a number; you get healthier by spending time in the right domain long enough for biology to change.

Heart rate training is geared toward adaptation, not the absolute number you can reach or stay at. If you’re unfit—metabolically speaking— the top end of zone 2 could be 115, even if your maximum heart rate is 190. This matters. Aerobic deficiency syndrome- being unable to sustain a long, low heart rate run or ride is a sign of poorly functioning mitochondria. And as we have discussed hundreds of times, your mitochondrial health and efficiency determine your overall health and your ability to resist various disease states or recover from unforeseen injuries and illnesses. Therefore, this conversation is essential.

The 5-zone model matters because your physiology changes across it.

Inigo San Millán has made this clearer than anyone. Heart rate is a proxy, not a purpose. The purpose is the metabolic outcome. Each zone recruits distinct systems, fuels, and cellular responses. In other words, each zone targets a different physiological mechanism in the energy partitioning… or how your cell creates ATP to fuel your effort.

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Zone 1–2: The Foundation Most People Skip

These are the zones almost no one spends enough time in because it sucks. It doesn’t feel like training. Heart rate is low. Breathing is easy. You can talk comfortably. Modern fitness culture reads that as weakness. In reality, this is where endurance, metabolic flexibility, and longevity are built. These efforts are primarily aerobic. Mitochondria dominate. Fat is oxidized cleanly with minimal lactate accumulation. The stimulus is gentle, but it must be long — because slow-adapting systems require time under load.

This is where:

• Mitochondrial density increases
• Capillary networks expand
• Lactate clearance improves
• Fat oxidation capacity rises
• Autonomic balance shifts parasympathetic- calming, restorative.
• Longevity pathways are up-regulated

Zones 1 & 2 are not glamorous, but they are foundational. It is slow medicine for metabolism. It improves healthspan, preserves muscle glycogen for higher intensities, and teaches the body to use fat as a primary fuel. You cannot bypass this. You cannot substitute it with maximal sweat. A lifetime aerobic engine is built here.

Many of you might argue, as influencers online do, that high-heart-rate domain work also drives mitochondrial density, and it does… but the context is essential, and low-heart-rate work is better at it.

Most runners never get fast, because they never got slow.

Mitochondrial biogenesis occurs across all training zones, but via different mechanisms and to varying degrees. Zone 2 (easy aerobic effort) drives mitochondrial biogenesis primarily through volume and duration. It activates PGC-1α - the master regulator of mitochondrial biogenesis - via AMPK signaling, creating slow, sustained signaling for mitochondrial development. This is where you build mitochondrial density and oxidative capacity most efficiently. Fat oxidation at these intensities also stimulates mitochondrial adaptation.

Zones 4-5 (high intensity) also stimulate mitochondrial biogenesis, but through different pathways. High-intensity work creates metabolic stress, activating PGC-1α via signals such as calcium flux, reactive oxygen species, and lactate. Lactate itself is a signaling molecule that promotes mitochondrial biogenesis. The stress from high-intensity training creates a powerful adaptive signal despite its shorter duration, leading to improvements in mitochondrial quality.

The research suggests both pathways work, but Zone 2 gives you more total mitochondrial volume because you can sustain it longer. High intensity provides potent signaling per unit time, but you can’t do it as frequently or for as long.

The combination is likely optimal: Zone 2 for base building and mitochondrial density, high intensity for metabolic stress adaptation and mitochondrial quality. For mitochondrial health, you want both. Zone 2 builds the engine. Zone 4-5 tunes it. Most aging athletes need more Zones 1 & 2 volume than high intensity, but skipping intensity entirely leaves adaptation on the table.

For Members

Below, I break down heart-rate training the way it actually works — not the way it’s marketed.

We’ll walk through:

• Why the 5-zone model matters only if you understand the biology underneath it

• Why Zone 3 traps most athletes in chronic fatigue with minimal adaptation

• How high-intensity zones improve mitochondrial quality

• The lactate shuttle, Type I and Type II muscle fibers, and why being able to use lactate as a fuel is a superpower,

• How too much red-zone work increases oxidative stress, injury risk, and metabolic fragility

• And finally, I will build you a base training protocol, a long-term, low-heart-rate training framework for runners and cyclists who want to stay fast, healthy, and capable for decades — not months

This isn’t about training harder.
It’s about training in a way that actually changes your physiology..