Demystifying Training Zones with Prof. Dr. Fabiano Pinheiro

Exercise as a 'Dose': Respecting Zones is Essential

Fabiano Pinheiro draws an interesting analogy between physical exercise and medication dosage. Although he emphasizes that exercise is not medicine — as one is a chemical substance and the other is a non-pharmacological treatment tool — the idea of a “dose” is crucial. Just as a doctor prescribes the correct dose of a medication, a coach prescribes an “exercise dose” that combines intensity, duration, frequency, and volume. This dose is designed to induce adaptations and improvements in the individual.

The importance of respecting these zones is a key point. Training at low intensity, for example, is like investing money that earns passive interest. It's not about "suffering" through every workout, but rather working intelligently, focusing on recovery as much as the stimulus. Current science, in fact, has directed more studies toward recovery, aiming to reduce wear and tear and optimize the body's response.

Unraveling Muscle Fibers: LED vs. Incandescent

To simplify the complex functioning of the body, Fabiano explains the types of muscle fibers using a lamp analogy:

• Type 1 Fibers (red): Equivalent to an 110 W LED bulb. They are highly resistant, economical, and durable, but produce little force. They predominatem in endurance activities.

• Type 2x Fibers (white): Analogous to a 220 W incandescent bulb. They consume a lot of energy, generate high tension (force), but are not very resistant and fatigue quickly.

• Type 2a Fibers (intermediate): These are a middle ground, producing more force than Type 1 and being more economical than Type 2x.

It's important to understand that the recruitment of these fibers is not an “on-off” switch, but rather an addition. When Type 1 fibers can no longer generate the necessary tension, the brain activates Type 2a, and if the effort is even greater, Type 2x. This overlap is crucial for athletes to understand that we never truly run “out of oxygen,” but rather experience a predominance of different energy systems.

A curious study, in which Fabiano participated and underwent a muscle biopsy, showed differences in fiber composition between untrained individuals and trained cyclists. Cyclists had a much higher percentage of Type 1 fibers. Furthermore, capillary density (blood supply to the fibers) is significantly higher in trained athletes, which improves the delivery of oxygen and nutrients, much like a highway with more exits.

The Body as an Energy Plant: Hydroelectric and Thermal Power

Fabiano uses another analogy to explain the energy systems:

• Aerobic System (Hydroelectric): High energy production capacity, like the Itaipu Dam. It's the body's “clean energy,” predominant in moderate intensity zones (Z1 and Z2), primarily using Type 1 fibers and free fatty acids. Sustainable for hours.

• Anaerobic System (Thermal Power): Activated when the aerobic system cannot sustain the energy demand alone. It generates more metabolic “pollution” (stress), using Type 2 fibers. This is the “help” that kicks in during heavier zones (Z3 and Z4).

Navigating Intensities: From Mild to Extreme

As exercise intensity increases, the body transitions through different domains:

• Moderate Domain (Z1-Z2): System stability, aerobic predominance. Here, the body can sustain effort for long periods.

• Heavy Domain (Z3-Z4): Metabolic stress increases, recruiting Type 2a fibers. The aerobic system approaches its maximum capacity, and the “thermal power” system begins to contribute more. There is still stability, but comfort decreases.

• Severe Domain (above Z4): Type 1 and 2a fibers are no longer sufficient, and Type 2x fibers are intensely recruited. There is a loss of system stability (second threshold or respiratory compensation point), with an abrupt increase in lactate and ventilation. This is the limit of suffering, where the body decides if it's worth continuing.

Strategies for Progress: Interval Training and Recovery

To train at the highest intensities of the severe domain without “breaking down,” the strategy is to “pay in installments.” HIIT or SIT workouts involve short bursts of high intensity (e.g., 60 seconds) followed by periods of active recovery (e.g., 4 minutes in Z1/Z2). This allows the athlete to reach peak efforts, generate metabolic stress, and improve neuromuscular learning, without completely burning out.

Recovery is where the magic happens. During rest, the body adapts, increasing its capacity for energy production and metabolite removal. Over time, recovery capacity improves, and the athlete can repeat more intense stimuli in less time.

Performance Tests: Complementary for Precise Training

The importance of performance tests, whether field-based (FTP) or laboratory-based (maximal incremental), is undeniable. Laboratory tests offer a “gold standard” in a controlled and reproducible environment, providing precise parameters for physiological thresholds. This allows the coach to adjust the “dose” of training with greater accuracy.

With training, physiological thresholds shift to the right (the athlete can maintain higher power in lower zones of perceived effort). Retesting periodically is crucial to readjust the zones, ensuring the stimulus remains effective. It's not enough to have a high VO2 max; performance is also determined by the position of thresholds and movement economy.

Communication between athlete and coach is key to success. Athlete feedback on sensations, fatigue levels, nutrition, and sleep allows the coach to modulate training, adjusting repetitions or recovery times, transforming the complex puzzle of training into a clear path for progress.

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To learn more about neuromuscular or cardiopulmonary assessments, Prof. Dr. Fabiano Pinheiro offers services at Labfab (@labfab.cienciadociclismo) in Tatuapé, east side of São Paulo. You can contact via Instagram or email at labfab.cienciadociclismo@gmail.com.br.