A breakdown of Marathon Handbook's analysis on lactate as a metabolic fuel. Learn why older endurance athletes should rely on carbs over experimental gels.
On September 17, 2026, Marathon Handbook published a comprehensive analysis clarifying the often misunderstood role of lactate in endurance sports. The publication examined how working muscles produce and utilize lactate during sustained exercise. This report challenges the outdated idea that lactate is merely a harmful waste product that causes fatigue. It also evaluates the recent trend of using oral lactate supplements and sodium bicarbonate in training. The findings offer practical boundaries for athletes attempting to optimize their nutrition protocols.
The central conclusion from the Marathon Handbook analysis is that lactate serves as a highly reusable metabolic fuel. It is not the physiological enemy that older training manuals often depicted. The body produces lactate continuously, even when a person is entirely at rest. Production naturally rises as exercise intensity increases and carbohydrate utilization scales up.
Instead of simply accumulating as waste, lactate acts as a resource for the entire body. Working muscles, the heart, and other tissues can actively consume it to sustain effort. Additionally, the liver performs a critical recycling function by converting circulating lactate back into usable glucose. This constant cycle of production and clearance means lactate is a fundamental part of human energy metabolism.
The human body is an incredibly efficient engine that constantly adapts to physical stress. When you push the pace during a tempo run, your muscles demand immediate energy. This demand accelerates the breakdown of carbohydrates, which naturally results in higher lactate production. Rather than shutting the body down, this response provides a critical energy lifeline when oxygen availability is limited.
The article highlights insights from exercise physiology researcher Aitor Viribay. He described lactate as a highly efficient and preferential fuel for the body. This expert observation explains why sports nutrition companies are suddenly so interested in the compound. Viribay raised the compelling possibility that exogenous lactate might eventually play an important role in advanced sports fueling.
Endurance athletes often view a lower blood lactate reading as direct proof of improved fitness. Marathon Handbook cautions strongly against this oversimplified assumption. A reduced lactate value does not automatically mean an athlete is performing better or experiencing less fatigue. It could simply indicate that the body is breaking down fewer carbohydrates at that specific moment.
Alternatively, a lower number might reflect more efficient metabolic clearance rather than lower initial production. Your liver and muscles might be consuming the fuel faster than it can accumulate in your bloodstream. While this is a positive physiological adaptation, the single number on the screen cannot tell you which mechanism is responsible. Relying solely on a single metric ignores the broader context of an athlete's physical output.
Athletes should measure success by their ability to run faster, generate more power, or sustain a hard effort for longer periods. A blood reading provides interesting context about exercise intensity, but it is not a standalone score of athletic capability. Treating it as the ultimate goal can distract from proven training principles. The publication argues that tangible performance outcomes remain the only relevant test of true improvement.
The endurance market has recently seen an influx of products promoted as oral lactate gels. Proponents suggest these supplements might provide additional fuel when traditional carbohydrate pathways reach their absorption limits. While the proposed mechanism sounds plausible, Marathon Handbook characterizes these products as strictly experimental. The translation from internal human physiology to an effective oral supplement is notoriously difficult.
For the ambitious athlete over 35, the practical takeaway is to maintain a critical distance from unproven supplement trends. The analysis explicitly states that oral lactate products are not a replacement for traditional carbohydrate fueling. Older athletes require reliable energy to support progressive overload and prevent excessive muscle breakdown during long sessions. Skipping established nutrition protocols in favor of an experimental gel introduces unnecessary risk to your training stability.
Older competitors should prioritize predictable energy delivery over theoretical shortcuts. Carbohydrates have decades of rigorous scientific literature proving their efficacy in extending human performance limits. The Marathon Handbook article stresses that experimental lactate gels lack this foundational level of controlled evidence. Until substantial trials show clear benefits, these products remain an interesting idea rather than a necessary tool.
Athletes who want to optimize their race day should review consistent carbohydrate strategies rather than chasing marginal gains. Building a dependable fueling routine takes precedence over testing every new supplement on the market. It is crucial to understand that researchers still need more controlled evidence before calling oral lactate an endurance breakthrough. Just because your muscles efficiently burn the lactate they produce naturally does not mean they can properly absorb it from a packet.
It is easy to confuse lactate gels with sodium bicarbonate because both products target intense physiological efforts. Marathon Handbook clarifies that these two substances serve entirely different proposed roles. While developers pitch lactate gels as a potential energy source, sodium bicarbonate functions specifically as a buffering agent. Bicarbonate does not work by eliminating lactate from the bloodstream.
Instead, it aims to manage acidity during highly intense efforts where metabolic buildup becomes a major limitation. This makes it a highly targeted option for short, intense intervals or specific race scenarios. It is not a general purpose fuel for a long Sunday run. The targeted nature of bicarbonate means it has a very narrow application window for most amateur runners.
Older athletes must also consider the practical drawbacks of adding bicarbonate to their routine. The publication warns that sodium bicarbonate carries a significant risk of causing gastrointestinal distress. A ruined stomach can easily derail a critical workout or an expensive race day. Athletes who follow a structured seasonal pacing framework should reserve such risky interventions for very specific, highly controlled situations.
The science is clear that carbohydrates remain the undisputed foundation for endurance performance. You should base your training and racing nutrition on easily digestible sugars that your body already knows how to process. Do not alter a proven routine just because a new product claims to leverage the lactate energy pathway. As you age, the margin for error in training load and nutritional recovery becomes noticeably smaller.
When you do evaluate a new supplement, look strictly at measurable improvements in your physical output. Ask yourself if the product helps you hold your target pace longer or recover more efficiently. Ignore claims that focus entirely on altering a blood metric without demonstrating a tangible performance benefit. Your goal is to cross the finish line faster, not to achieve a specific chemical reading in your bloodstream.
Measuring progress requires a mature perspective as you navigate different training blocks. The temptation to obsess over physiological data points is stronger than ever. However, the veteran athlete understands that true athletic maturity means trusting your physical sensations alongside actual timed performance. Your training environment should focus on building sustainable resilience and maintaining consistent output.
It is wise to wait for strong controlled research before spending money on unproven sports nutrition. Keep your attention on consistent habits, proper rest, and the established fundamentals of endurance science. For athletes looking to refine their broader approach, focusing on foundational endurance training resources is a much safer investment.
Endurance athletes should maintain established carbohydrate routines and treat lactate supplements as unproven experiments until clear performance benefits are firmly demonstrated.
Follow ReEndure for practical insights on endurance training, recovery, nutrition and healthy aging. Stay connected for new articles, research led guidance and ideas to help you perform better for longer.
Read practical ideas on endurance training, recovery, nutrition and healthy aging to keep progressing for years to come.
Read the Blog