Most training plans treat every athlete the same. You get a set of zones, a weekly structure, and a progression model that assumes your physiology is identical to everyone else following the same plan. It is not. Your metabolic profile determines how your body produces energy, and that profile should dictate how your training is structured.
When we test athletes using DFA Alpha1 analysis, we identify two thresholds: HRVT1 (the aerobic threshold) and HRVT2 (the anaerobic threshold). The relationship between those two thresholds reveals which of three broad metabolic archetypes an athlete falls into. Each archetype responds to training differently, and each needs a different approach to improve.
Type 1: The Glycolytically Dominant Athlete
This athlete has a low first threshold and a narrow gap between HRVT1 and HRVT2. Their aerobic system is underdeveloped relative to their anaerobic capacity. They can produce impressive short efforts, but they fade badly over longer durations. In a triathlon context, they often feel strong on the bike but fall apart on the run.
The glycolytically dominant athlete relies heavily on carbohydrate metabolism at intensities that should be comfortable. Their body reaches for anaerobic energy systems earlier than it needs to, which means they burn through fuel faster and accumulate fatigue more rapidly. The aerobic zone that should form the foundation of their endurance performance is compressed into a narrow band at very low intensities.
What this athlete needs is extensive aerobic development work. Long, consistent sessions below HRVT1. Tempo work in the zone between the two thresholds - what is often called sub-threshold training. A deliberate, patient approach to expanding the aerobic base so that the first threshold shifts upward and the gap between the two thresholds widens. High-intensity interval work should be minimal until the aerobic foundation is established.
Type 2: The Balanced Athlete
This athlete has a moderate first threshold and a proportional gap between HRVT1 and HRVT2. Neither energy system is dramatically over- or underdeveloped. They perform consistently across durations and tend to pace well in races because their metabolic profile supports a steady output.
The balanced athlete is in the most flexible position from a training perspective. They can benefit from work across all three zones because no single system is the obvious limiter. However, this does not mean their training should be generic. The balanced profile still has nuances. The first threshold might sit slightly low relative to the second, suggesting room for aerobic development. Or the second threshold might be the limiter, suggesting that targeted high-intensity work will produce the biggest gains.
The key for the balanced athlete is identifying which threshold has the most room to move and applying focused training stimulus there, while maintaining the other system. A pyramidal distribution, with the majority of volume below HRVT1, meaningful work between the thresholds, and targeted sessions above HRVT2, typically works well for this archetype.
Type 3: The Aerobically Dominant Athlete
This athlete has a high first threshold and a wide gap between HRVT1 and HRVT2. Their aerobic system is well developed. They can sustain moderate intensities for long periods without excessive fatigue. They tend to perform well in longer events but may lack top-end speed and struggle in shorter, more intense races.
The aerobically dominant athlete has already built a strong foundation. Their first threshold sits high, which means a large proportion of their performance range is fuelled aerobically. The limiter for this athlete is usually the second threshold, the ceiling. They have headroom above HRVT1 that they cannot fully exploit because HRVT2 has not shifted upward to match.
What this athlete needs is targeted high-intensity work above HRVT2 to raise the ceiling. VO2max intervals, threshold efforts at and above the second threshold, and race-specific intensity work. The aerobic base is already there. Continuing to pile on easy volume will produce diminishing returns. The biggest gains come from pushing the top end upward while maintaining the foundation underneath.
Why This Matters for Your Training
The problem with generic training plans is that they cannot account for these differences. A plan that prescribes 80 percent easy and 20 percent hard might be perfect for a glycolytically dominant athlete who needs aerobic development, but it would be suboptimal for an aerobically dominant athlete who needs ceiling work. A plan heavy on VO2max intervals might accelerate the aerobically dominant athlete but would dig a deeper hole for the glycolytically dominant one.
You cannot know which archetype you are from an FTP test, a time trial, or a race result. You need to measure both thresholds directly. Once you have that data, the training prescription becomes clear. The guesswork disappears, and every session has a defined purpose tied to your specific physiology.
Profiles Change Over Time
Your metabolic archetype is not fixed. As training shifts your thresholds, your profile evolves. A glycolytically dominant athlete who commits to aerobic development will gradually shift toward a balanced profile. An aerobically dominant athlete who adds ceiling work will see HRVT2 rise, narrowing the gap from the top rather than the bottom.
This is why regular retesting matters. A single test gives you a snapshot. Repeated testing over months and years shows you the trajectory. It confirms whether the training is producing the intended physiological adaptation, or whether the prescription needs to change.
Your metabolic profile determines what training you need. A generic plan cannot account for that. Test, profile, prescribe, retest.