Using Blood Lactate Response to Guide Training Progression

By Renee Eastman,
CTS Premier Coach

Part 4 of Leveraging Blood Lactate Response in Training: Using Blood Lactate Response to Guide Training Progression  

There are many ways to structure training throughout a season to achieve similar outcomes in terms of fitness and performance. The brilliance of human physiology is that applying stress to any point along the spectrum from easy to maximum effort will result in far-reaching adaptations. Going easy (Zone 1and 2) can increase VO2 max, power at LT2, and fat oxidation at LT1. Going super hard for less time can result in many of the same adaptations. That gives athletes and coaches a lot of flexibility when designing and modifying training schedules. It also means we need a good understanding of how to monitor progress and measure meaningful changes. Here’s how we can use blood lactate as a good way (but not the only way) to guide training progression.

Background

In Part 1, we discussed how blood lactate response helps establish precise training zones based on the aerobic threshold (LT1) and the anaerobic threshold (LT2). Part 2 covered the benefits of training along the lactate curve-first below LT1 in Zone 2, then Part 3 talked about training in the important space between LT1 and LT2 in Zones 3 and 4.

In this final section, we examine how blood lactate response provides critical insights into training effectiveness and physiological adaptations. Understanding these changes allow athletes to make data-driven decisions and optimize their training to achieve peak performance.

Annual Periodization: Structuring Training for Optimal Adaptation

Periodization is a systematic approach to training that manipulates intensity, volume, and recovery to maximize performance while minimizing fatigue and minimizing the risk of overtraining. Breaking the training cycle into distinct phases ensures progressive overload and adaptation.

• Base Phase – Emphasis on LT1 and Zone 2

The base phase focuses on aerobic development by training focused in Zone 2 (below LT1), which enhances fat oxidation, mitochondrial efficiency, and lactate clearance capacity. This phase consists of long, steady-state endurance rides or runs at 55-75% of LT2 (FTP) to build metabolic efficiency.

• Early Build Phase – Introducing Zone 3 and Lactate Clearance Training

As training progresses, Zone 3 (Tempo, Sweetspot Tempo) efforts are introduced to improve lactate clearance and sustain moderate lactate levels. Training in this range (75-94% of LT2) helps develop the ability to clear lactate effectively while sustaining moderate-intensity efforts. Typical workouts involve sustained efforts lasting 1-3 hours.

• Late Build Phase – Pushing LT2, Zone 4 and Threshold Development

During this phase, training near LT2 (Threshold/Zone 4) enhances tolerance to lactate accumulation, improving the ability to sustain higher-intensity efforts. Intervals at 95-105% of LT2 are structured in blocks of 10- to 20-minute intervals, with total efforts accumulating 30-60 minutes time-in-zone.

• Peak & Specialize/ Race-Specific Training – High Lactate Exposure in Zone 5+

In the peak phase, race-specific training involves intensities above LT2 (Zones 5 and higher). This phase conditions the body for rapid lactate clearance and improved anaerobic performance. Intervals at 106%+ FTP generate peak lactate levels (>5.0 mmol/L), simulating race conditions.

• Recovery and Transition Phases

Following peak training, athletes enter a recovery or transition phase to restore metabolic balance and reduce fatigue. Training intensity remains low, staying below LT1 (Zones 1-2) to facilitate recovery.

Blood Lactate and Training Progression  

A key challenge for coaches and self-coached athletes is determining whether to continue with more of the same training or progress to a new type, volume, or intensity of training. Blood lactate response provides a valuable indicator for evaluating training adaptations.

Base to Build: Look for Better Metabolic Efficiency

Metabolic efficiency refers to the body’s ability to utilize fat as an energy source while conserving glycogen. A well-trained athlete can sustain endurance efforts with minimal carbohydrate depletion, prolonging time to fatigue.

Training at lower intensity below LT1 in Zone 2 allows an athlete becomes a better Fat Burner. We see this progression in lactate response (pictured below) from early base (top) with to late base training (bottom) in which we see the overall higher absolute fat oxidation (grey area represents fat oxidation in grams/minute). This training has also moved LT1 from 72% of LT2/ FTP by power to 78% in this example. Recall the standard estimation that LT 1 is calculated at 75% of LT2/ FTP.

Lab testing may be the most accurate way to determine these changes, but even without access to lactate testing athletes may notice other changes that are associated with better metabolic efficiency in other ways:

• Lower Heart Rate at given pace or power below LT2.
• Reduced Perceived Effort at given pace or power below LT2.
• Reduced Heart Rate Drift (Aerobic Decoupling) at consistent pace or power.
• More Stable Blood Sugar and energy levels on longer rides (fewer bonks on long rides).

Moving from Base to Build can be determined by seeing a plateau in metabolic efficiency and occurs with the shift of LT1 to a higher intensity. However, for the time-crunched athlete this decision is often driven by the limit of Zone 2 volume they can do or by timing before their key event.

Early Build to Late Build Phase – Look for Enhanced Lactate Clearance

Lactate clearance is the ability of the body to remove lactate from the muscles and bloodstream and either recycle it for energy in slow-twitch muscle fibers or shuttle it to other tissues for metabolism. Training in Zone 3 improves this capacity through:

• Increased Mitochondrial Density: More mitochondria improve the oxidative capacity of muscle cells, allowing them to use lactate as an energy source.
• Improved Lactate Shuttle System: Slow-twitch muscle fibers, the liver, and the heart become more efficient at oxidizing lactate for fuel.
• Enhanced Capillary Density: Increased blood flow to working muscles improves the transport of lactate to areas where it can be used or cleared.
• Higher Activity of Lactate Transport Proteins (MCT1 & MCT4): These proteins regulate the movement of lactate in and out of muscle cells, allowing better distribution and utilization across different tissues​.

Training in Zone 3 shifts the body toward greater carbohydrate utilization and improves Metabolic Flexibility, which is the body’s ability to efficiently switch between fuel sources (fats and carbohydrates) depending on energy demands and availability. While fat oxidation is critical for endurance, efficient carbohydrate metabolism is essential for sustained high-intensity performance.

Late Build to Specialization: Look for Improved Lactate Tolerance  

Lactate tolerance refers to the body’s ability to sustain high-intensity efforts despite accumulating lactate and hydrogen ions, which contribute to muscle fatigue and acidosis. Training in Zone 4 and higher improves lactate tolerance through:

• Increased Buffering Capacity: Muscles produce more buffering agents (such as bicarbonate and carnosine) to counteract the acidic effects of lactate accumulation.
• Greater Anaerobic Enzyme Activity: Training at high intensities upregulates enzymes involved in anaerobic glycolysis, improving short-term power output.
• Neuromuscular Adaptations: The nervous system becomes more efficient at recruiting fast-twitch muscle fibers, improving explosive power and lactate handling.

In the lab we will see the impact of enhanced clearance and tolerance in the shape of the lactate curve (pictured below.)  A prolonged lactate curve indicates lower lactate response to intensity, an improvement in ability to sustain moderate lactate levels, and a shift of LT2 to a higher pace or power output.

Outside of the lab, athletes who improve lactate tolerance and clearance experience:

• Reduced Perceived Effort lower at higher intensities.
• Lower Heart Rate for the same workload.
• Increased Time to Exhaustion: Athletes can hold near-threshold efforts for longer without fatigue.
• Improved Power at FTP: Better power on field tests.

Specialization: Maximize Lactate Production and Clearance for Peak Performance

Moving closer to peak performance it is important to include high-intensity workouts. Above lactate threshold (LT2) the body shifts from steady-state performance to anaerobic energy production. Training at this high intensity optimizes performance by improving:

• Lactate Production Capacity – Greater glycolytic activity supports maximal power output.
• Lactate Tolerance– Repeated exposure to high lactate enhances buffering and clearance.
• VO2 max and Oxygen Uptake: High-intensity training improves oxygen delivery and efficiency.
• Fast-Twitch Fiber Adaptation – Enhanced glycolytic enzyme activity and anaerobic capacity improve sprinting and surging ability.
• Better Recovery – Faster lactate clearance between intervals enables sustained high-intensity performance.

Conclusion

Periodizing training based on lactate response enables structured progression while balancing workload and recovery. In the base phase, Zone 2 training dominates, enhancing metabolic efficiency. The build phase introduces Zone 3 and Zone 4 efforts, improving sustainable power and lactate clearance. As competition approaches, high-intensity intervals in Zones 5–6 enhance anaerobic power and lactate tolerance, sharpening race readiness. Monitoring lactate trends throughout these phases allows precise workload adjustments, optimizing performance gains and ensuring peak race readiness.

References

Brooks, G. A. (2018). The science and translation of lactate shuttle theory. Cell metabolism, 27(4), 757-785.

Esteve-Lanao, J., Foster, C., Seiler, S., & Lucia, A. (2007). Impact of training intensity distribution on performance in endurance athletes. Journal of Strength and Conditioning Research, 21(3), 943-949.

Seiler, S. (2010). What is Best Practice for Training Intensity and Duration Distribution in Endurance Athletes? International Journal of Sports Physiology and Performance, 5(3), 276-291. Retrieved Jan 15, 2025.

Seiler, K. S., & Kjerland, G. Ø. (2006). Quantifying training intensity distribution in elite endurance athletes: is there evidence for an “optimal” distribution? Scandinavian Journal of Medicine & Science in Sports, 16, 49-56.

About the Author

Renee Eastman is a Premier Coach for Carmichael Training Systems with a bachelor’s and master’s degree in exercise physiology. She is a certified USA Level 1 Coach, NSCA Strength and Conditioning Specialist, and NASM Nutrition Coach. A former competitive cyclist and six-time masters’ national champion, Renee has been with CTS since 2001.