Zone 2 for Gravel Biking: It’s Not Just About Riding Slow

In recent years, “Zone 2 Training” has become one of the most frequently mentioned keywords in the endurance sports community, but most discussions suffer from two problems. First, many people treat it as a panacea, as if simply riding without getting out of breath automatically upgrades mitochondrial and fat metabolism infinitely. Second, many people fail to clarify what Zone 2 actually refers to, so the same term often refers to completely different things across five-zone power systems, three-zone models, coaching vernacular, and social media videos.

For gravel biking, this confusion is particularly dangerous. Because gravel is not uniform, stable asphalt cruising. It often involves long-duration endurance output, unstable pedaling caused by loose sand and gravel, torque fluctuations from alternating gentle and short slopes, additional fatigue from upper body isometric contractions, and race situations where nutrition and pacing are more prone to loss of control. If you set your so-called Zone 2 too high, you won’t get ideal aerobic foundations; instead, every endurance session becomes low-quality moderate-intensity fatigue. But if you set it too low and don’t spend enough time, you may just accumulate mileage without generating sufficient peripheral adaptations.

The core argument of this article is clear: For gravel riders, if the Zone 2 mentioned in the question is to stand up scientifically, it should primarily be understood as a low-intensity endurance zone located just below the first lactate threshold (LT1). Its value lies not in “popularity,” but in its ability to accumulate large metabolic fluxes in a recoverable manner, stimulate angiogenesis, improve local oxygen delivery, increase the proportion of lipid oxidation, and keep your fatigue curve low on long gravel rides. However, it must also be made clear: Zone 2 is not everything; high intensity remains indispensable.

I. First, Correct the Terminology: What Social Media Calls Zone 2 is Often Actually Below LT1 in Research

The most common confusion currently exists between “five-zone heart rate/power system Zone 2” and the “Seiler three-zone model.”

Recent expert consensus indicates that if “Zone 2 training” is treated as an independent training concept, it is more suitable to be defined as a low-intensity endurance zone located just below the first lactate or first ventilatory threshold. This definition is very important because LT1 and angiogenesis mentioned in the question align better with this usage than the moderate-intensity zone in the Seiler three-zone model.

Therefore, this article will adopt the following terminology logic in the subsequent sections:

1. Low-intensity endurance zone below LT1: The Zone 2 referred to in this article.
2. Between LT1 and LT2: Referred to as moderate-intensity or tempo/steady zone.
3. Above LT2: Referred to as high-intensity zone.

This is not being pedantic about words, but to avoid making training plans incorrectly. Because for gravel riders, what truly needs to be stacked in large quantities is recoverable output below LT1, not pressing every endurance ride into the gray zone where lactate is continuously rising.

II. Why Gravel Biking Relies Heavily on Large Amounts of Work Below LT1

Currently, peer-reviewed literature specifically targeting gravel is still significantly less than that for road cycling and XCO mountain biking. Therefore, in terms of mechanism inference, we must honestly draw inspiration from off-road cycling and mountain biking physiological research. This is not concept-switching, but because gravel itself sits between road endurance and off-road variable loads: total duration is often very long, but output is not as smooth as traditional road time trials.

For gravel riders, large amounts of work below LT1 solve at least four things:

1. Improve Metabolic Stability for Long-Duration Output

The success or failure of gravel events is rarely decided solely by 5-minute maximum power. More often, the difference comes from whether you can maintain effective pedaling, stable nutrition, control upper body tension, and manage local muscle endurance decline after 3 to 8 hours. Long-duration training below LT1 allows for lower metabolic stress at the same power, allowing you to spend more race time in a “controllable” physiological state.

2. Reduce Cumulative Costs from Power Fluctuations

Gravel and unpaved terrain force you to repeatedly handle small accelerations, insufficient traction, hard cornering exits, and torque pulling on short slopes. If basic aerobic capacity is insufficient, these small fluctuations will quickly push you into a state of higher glycolytic burden. Large amounts of work below LT1, while seemingly unstimulating, are improving your tolerance base for these “non-ideal outputs.”

3. Improve Nutrition Error Margin

Long-distance gravel events often face problems such as sparse supply points, bumpy roads making eating difficult, and changing weather conditions. If the aerobic base is thick enough, under the same race pace, the relative dependence on carbohydrates is lower, and one missed nutrition opportunity won’t immediately cause a crash.

4. Improve Endurance Durability

Recent endurance sports research places increasing emphasis on durability, which is the ability to maintain original physiological and mechanical performance after long-duration exercise. For gravel, this is almost more important than 20-minute power in fresh condition. Long-duration riding below LT1 is one of the core means to build durability.

III. What is Actually Trained Below LT1: Not Just Fat Metabolism, But Also Reconstruction of the Microvascular Network

The most common statement about Zone 2 online is “train fat metabolism, build mitochondria.” The direction is not wrong, but it is too narrow. For true endurance performance, the local oxygen delivery system is equally important, and angiogenesis is a key part of it.

When you maintain work below LT1 for a long time, skeletal muscles repeatedly experience:

1. Continuous but not excessive increase in blood flow;
2. Repeated muscle contraction and relaxation;
3. Increased local metabolic demand, but still within a stable processing range;
4. Endothelial cells exposed to repeated shear stress;
5. Signal pathways related to angiogenesis are gradually activated.

These stimuli promote microvascular bed remodeling, making the vascular distribution around muscle fibers more favorable for oxygen and substrate exchange. For gravel riders, this does not represent abstract “better endurance,” but rather more concrete things:

Therefore, a truly mature endurance viewpoint does not separate mitochondria and microvasculature. Mitochondria decide how you use oxygen, microvasculature decide if oxygen can be delivered smoothly to where it needs to go.

IV. Angiogenesis is Not Mysticism: It Has Clear Mechanical and Molecular Mechanisms

Exercise-induced angiogenesis is mainly not decided by a single magical hormone alone, but driven jointly by hemodynamics, mechanical stretch, and local metabolic environment.

1. Shear Stress is an Important Signal for Long-Duration Low-Intensity Training

When muscle blood flow increases repeatedly, the shear stress generated by blood flow on vascular endothelium increases. Literature indicates that this mechanical stimulus can promote endothelial function and vascular remodeling, which is an important driving source for capillary splitting and related vascular adaptations. For long-duration training below LT1, the value lies in its ability to provide long-duration, repeatable, and recoverable shear stress exposure.

2. VEGF, NO, and Endothelial Signaling Pathways Are Involved

After exercise, growth factors and signals related to angiogenesis in skeletal muscle are upregulated, including VEGF and nitric oxide (NO) related pathways. These are not only triggered by explosive high-intensity efforts; moderate to low intensities with sufficient duration and total volume can also generate effective signals.

3. Capillary Growth Is Not a Single Form

Research indicates that capillary growth may occur through different forms such as splitting or sprouting. Simplified understanding: when your training consistently provides appropriate blood flow and mechanical muscle stimulation, the microcirculatory network adjusts toward more efficient exchange structures.

4. But This Does Not Mean Zone 2 Is the Only Effective Zone

Here, science must be explained fully. Recent systematic reviews and meta-analyses do not support the over-glorified claim that “only Zone 2 can best improve mitochondrial or fat oxidation capacity.” Certain high-intensity modes can also effectively stimulate mitochondrial or microvascular adaptations. What truly determines effectiveness is not a single intensity myth, but:

1. Your total training volume;
2. The configuration of low and high intensities;
3. How much recovery you can achieve each week;
4. What race demands you are preparing for.

Therefore, the more precise statement for gravel riders should be: Massive work below LT1 is the foundation, not the entirety.

V. How to Define Your Own LT1: Fixed Percentages Are Often Inaccurate

A common mistake made by many riders is directly using 70% of maximum heart rate, 60-70% of FTP, or a watch’s automatic zone, then treating it as absolute truth. The problem is that literature and practice show significant individual differences. For some individuals, 70% of FTP is still below LT1; for others, they may already be in moderate intensity.

A more reliable sequence is as follows:

1. Laboratory Lactate or Ventilation Testing

This is the most direct method. By observing the first systematic rise in lactate or changes in ventilatory response during progressive testing, LT1 can be found more precisely. The disadvantages are high cost and infrequent testing.

2. Field Lactate Testing

If you have a portable lactate analyzer, you can perform 3 to 5 segments of steady power riding to find the position where lactate remains close to baseline but is approaching the endurance upper limit. This has higher individualized value than relying solely on heart rate.

3. Talk Test and Subjective Breathing Assessment

The literature basis for the Talk Test is more solid than many imagine. If you can still comfortably speak complete sentences while riding, your breathing rhythm is stable, and you do not have frequent urges to gasp, it usually indicates you are still below the first ventilatory or lactate threshold. It does not have laboratory precision, but it is very practical for daily training schedules.

4. Heart Rate Drift During Long-Steady Riding

A practical method very useful for gravel riders is to observe power-heart rate decoupling during 90 to 180 minutes of steady riding. If power is fixed but heart rate continues to rise significantly in the latter half, it often indicates the intensity is too close to or exceeds your current sustainable low-intensity zone, or there are issues with fueling, hydration, or environmental heat stress.

The following table can be used for simplified interpretation:

5. HRV-Derived Thresholds Can Serve as an Aid, But Do Not Over-Worship Them

In recent years, some have also used heart rate variability indicators to estimate the first threshold. These tools have research foundations, but their validity is still affected by measurement conditions, algorithms, and individual differences. They can serve as monitoring aids but cannot replace comprehensive interpretation.

VI. For Gravel Riders, Fatigue Control Is More Important Than Nominal Zone 2

Even if called Zone 2, some workouts build the foundation, while others slowly wear you down. The difference usually does not lie in average power, but in fatigue cost.

What You Should Track Is Not a Single Intensity, But These Four Things

1. Heart Rate Drift: Whether heart rate spikes significantly in the latter half at the same power.
2. Cadence and Torque Stability: Whether there is excessive low-cadence, high-torque pedaling on gravel, leading to excessive local muscle fatigue.
3. Subjective Muscle Tension: Especially in hip extension, lower back, forearms, and neck/shoulders.
4. Fueling Execution Quality: Whether hourly carbohydrates, water, and sodium are following the plan.

For gravel training schedules, low-intensity training is most easily disrupted by two things:

1. Route Selection Is Too Hard

If your “Zone 2 long ride” requires pedaling up a 15% gravel hill every 10 minutes, the actual workout has become a torque endurance and repeated supra-threshold stimulus, no longer purely building below LT1.

2. Fueling Is Poor

Low-intensity long rides do not mean you can skip fueling entirely. Insufficient fueling causes larger heart rate drift in the latter half and reduced movement quality, leading you to mistakenly think you lack “Zone 2 endurance,” when in fact it is a heat and energy management issue.

VII. How to Structure Your Schedule: The Roles of Zone 2 in Base, Build, and Race Prep Phases Are Completely Different

1. Base Phase: Use Large Amounts of Time Below LT1 to Build Microvascularity and Durability Foundation

Suitable arrangements:

The most important thing in this phase is time quality. If you ride near or slightly above LT1 every time, doing a large total volume will quickly lead to recovery problems.

2. Build Phase: Retain Zone 2 Volume, But Add More Race-Specific Stimuli

Once the foundation is established, add the following without compromising recovery:

1. Long-hill tempo;
2. Repeated short-hill torque segments;
3. Over-under or terrain variation workouts close to race rhythm;
4. Ability to maintain stable output after technical sections.

However, these workouts must still be built on a sufficient base of low-intensity volume; otherwise, gravel riders easily fall into the state of “tired every week but never training correctly on any given day.”

3. Race Prep Phase: Zone 2 Is Not Eliminated, But Allows High Intensity to Truly Land

Some people cut all low-intensity work during the race prep phase, which is a common mistake. High-intensity efforts and race simulations during the race prep phase need low-intensity days to absorb fatigue. For gravel races with long total durations and high risk of late-race decline, maintaining sufficient riding below LT1 before the race is a necessary condition to maintain freshness and durability.

VIII. Data Analysis Example: The same gravel rider, two seemingly identical long rides, with vastly different actual quality

Assume a rider’s lab results show:

• FTP: 285 W
• LT1: 195 W
• Body weight: 68 kg
• Primary goal: 5-hour gravel race

He performs 3-hour endurance rides for two consecutive weeks, both appearing to be Zone 2, but the content is as follows:

On the surface, Week 1 seems more “diligent,” but from the perspective of LT1 and fatigue management, Week 2 is more consistent with the logic of endurance base training. The mistakes in Week 1 include:

1. Average power was slightly higher than LT1;
2. Normalized power was on the high side, indicating overly aggressive terrain handling;
3. Insufficient fueling, amplifying cardiac drift in the latter half;
4. High next-day fatigue, compromising the quality of subsequent training sessions.

This is the data-driven mindset most needed for gravel training: Don’t just look at how long you rode; look at whether this session is leading you toward adaptation or ineffective fatigue.

IX. Common Mistakes: Deifying, Narrowing, and Messing Up Zone 2, Leading to Slower Progress

1. Pushing all endurance sessions to the upper limit of LT1

Many people think “the closer to the limit, the more effective.” In reality, if you ride right at LT1 every time, the total fatigue cost is much higher, and your weekly training volume and recovery are easily compromised.

2. Complete lack of high intensity

Recent commentary has clearly warned against packaging Zone 2 as the sole optimal solution. If training volume is not high and there is a complete lack of high-intensity stimulation, your cardiorespiratory ceiling, anaerobic capacity, and race-pace variability will be limited. Gravel, in particular, requires handling short climbs and gear changes; you cannot prepare for it solely by riding slowly.

3. Treating indoor ERG steady-state riding as specific gravel preparation

Indoor training can build stable metabolic output, but fatigue in gravel often stems from terrain changes, torque fluctuations, handling, and fueling interruptions. If you don’t validate this in outdoor terrain, your low-intensity endurance may not fully transfer to race conditions.

4. Neglecting strength and bike stability

Fatigue on gravel roads is not just cardiorespiratory; it also involves the arms, core, hips, and lower back. If your posture lacks stability, even if your aerobic system can hold up, you may be dragged down by localized fatigue first.

5. Using fixed percentages as a permanent answer

Weather, fatigue, altitude, the previous day’s session, and fueling status will all change your perceived exertion and heart rate performance below LT1. Your Zone 2 should not just be a static wattage number; it needs to be calibrated using breathing, cardiac drift, and post-session recovery.

X. Conclusion: For gravel riders, the true value is not “riding Zone 2,” but building usable durability through training below LT1

If this article could be condensed into one sentence, it would be: The true scientific value of Zone 2 for gravel cycling lies in using high-volume, recoverable, and sustainable training below LT1 to reshape your local oxygen supply network and fatigue curve.

This type of training is important not because it is trendy, but because the nature of gravel racing dictates that you must:

1. Maintain metabolic stability for long periods;
2. Preserve movement quality amidst irregular torque fluctuations;
3. Execute fueling and pacing strategies through the latter stages;
4. Ensure high-intensity days have the recovery space to be performed effectively.

Angiogenesis, mitochondrial adaptation, improved lipid oxidation, decreased cardiac drift, and improved late-stage durability—these are not miracles that happen in isolation, but the result of long-term, systematic training configuration. The most practical strategy for a gravel rider is not to blindly worship Zone 2, but to:

1. Find your LT1 accurately;
2. Ensure that high-volume low-intensity is truly low enough;
3. Monitor fatigue costs with data;
4. Retain necessary high-intensity and technical stimulation on this foundation.

Only then is Zone 2 not just a slogan, but a true chassis that allows you to still put out power, make decisions, consume fuel, and maintain your pace in the final stages of a gravel race.

References and Further Reading

1. Van Hooren B, et al. What Is “Zone 2 Training”?: Experts’ Viewpoint on Definition, Training Methods, and Expected Adaptations.
2. Storoschuk KL, Moran-MacDonald A, Gibala MJ, Gurd BJ. Much Ado About Zone 2: A Narrative Review Assessing the Efficacy of Zone 2 Training for Improving Mitochondrial Capacity and Cardiorespiratory Fitness in the General Population.
3. Mølmen KS, et al. Effects of Exercise Training on Mitochondrial and Capillary Growth in Human Skeletal Muscle: A Systematic Review and Meta-Regression.
4. Haas TL, et al. Exercise-induced skeletal muscle angiogenesis: impact of age, sex, angiocrines and cellular mediators.
5. Egginton S. Capillary growth in human skeletal muscle: physiological factors and the balance between pro-angiogenic and angiostatic responses.
6. Herold M, et al. Metabolic regulation of exercise-induced angiogenesis.
7. Arriel RA, et al. Current Perspectives of Cross-Country Mountain Biking: Physiological and Mechanical Aspects, Evolution of Bikes, Accidents and Injuries.
8. Smekal G, et al. Physiological Demands of Simulated Off-Road Cycling Competition.
9. Reed JL, Pipe AL. The talk test: a useful tool for prescribing and monitoring exercise intensity.

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