We all think we know about lactate right? It’s just a byproduct that gets produced when our muscles are running in low oxygen state and using glycogen for fuel. So what?
If that’s been your view then it’s time to pay a lot more attention to lactate. By understanding its role it can really help unlock performance gains.
The first misconception to deal with is that it’s just a byproduct. Thanks to the work of Dr George Brooks at University of California, we now know that far from being a waste product, lactate is critical for the body and muscles to utilise glycogen during exercise. Muscle fibres are classified into two main types: glycolytic and oxidative fibres. During exercise, the demand for energy is increased and glycolytic fibres cover this demand by catabolising glucose, which brings, as a consequence, increases in a substance call pyruvate. When pyruvate production exceeds the glycolytic muscles fibre capacity to consume pyruvate, it is reduced to lactate. Lactate then gets transported out of the cells and into the blood stream. Our oxidative muscle fibres can then metabolise this lactate as fuel via mitochondria. (It is important to note that lactate may also be shuttled to the heart where it is used as an energy source and to the liver for glucose synthesis). Brooks termed this the ‘lactate shuttle theory’.
The lactate shuttle theory brought to the field a new research focus: lactate as a signalling molecule. Lactate has many benefits during exercise: lactate transport serves as an indirect regulator of muscle acidosis, and lactate itself as an effective energy source. This is why pro athletes and coaches, are focused on measuring lactate during exercise to understand where the boundaries lie for athletes moving from the more oxidative state to a more glycolytic state. It’s also why people like Inigo San Millan extol the benefits of a higher percentage of zone 2 training, which helps to develop a greater density of mitochondria, which in turn can help utilise lactate as fuel. The flipside being that the higher intensity training helps drive mitochondria efficiency and hence lactate clearance referred to above.
However, latest research suggests that lactate plays a far greater role and there may be another lactate shuffle in play. Researchers affiliated with the University of California, Berkeley recently published a study titled "Enteric and systemic postprandial lactate shuttle phases and dietary carbohydrate carbon flow in humans".
The study investigated how the body processes dietary carbohydrates, specifically glucose, after a meal. Traditionally, it was believed that excess glucose is directly converted into glycogen in the liver. However, the study introduced the concept of a postprandial lactate shuttle (PLS), suggesting that dietary glucose is first metabolised into lactate in the gut before being transferred to the liver for glycogen storage.
The researchers found evidence of two phases of the PLS in young, healthy individuals. The first phase involves the production of lactate in the gut from glucose, followed by a secondary phase where lactate is used as a vehicle for distributing and metabolising dietary carbohydrate carbon throughout the body. This challenges the idea that lactate production is only due to lack of oxygen in muscles.
In simpler terms, the study suggests that lactate plays a significant role in how the body processes and distributes carbohydrates after a meal. It proposes that lactate is a key player in managing the challenges posed by dietary carbohydrates and that it is not solely a byproduct of muscle activity in low oxygen conditions.
What impact does this study have for athletes?
This study on the postprandial lactate shuttle phases and dietary carbohydrate carbon flow in humans can have significant implications for athletes. Understanding how the body processes dietary carbohydrates, particularly the role of lactate in carbohydrate metabolism, can provide valuable insights for athletes looking to optimise their performance and recovery.
Athletes rely heavily on carbohydrates for energy during exercise, and knowing how the body handles dietary carbohydrates post-meal can help athletes better fuel their training and competition. By recognising the importance of lactate in carbohydrate distribution and metabolism, athletes can potentially adjust their nutrition strategies to enhance glycogen storage and utilisation, leading to improved performance.
Furthermore, the study challenges traditional beliefs about lactate production, suggesting that it is not solely a byproduct of muscle activity in low oxygen conditions. This new perspective may prompt athletes (and us coaches) to reconsider how they interpret lactate levels and utilise this information to tailor training and nutrition plans for better athletic outcomes.
Understanding the role of lactate in carbohydrate metabolism can be crucial for optimising an athlete's efficiency at utilising lactate:
Improved Energy Production: By recognising lactate as a major vehicle for carbohydrate carbon distribution and metabolism, athletes can potentially enhance their energy production during exercise. Efficient utilisation of lactate as a fuel source can contribute to sustained energy levels and improved performance.
Enhanced Endurance: Athletes with a better understanding of how lactate is processed and utilised in the body can potentially improve their endurance capacity. Optimising lactate utilisation can help delay the onset of fatigue and improve overall endurance performance.
Training Adaptations: Knowledge of the postprandial lactate shuttle phases can inform training strategies aimed at improving lactate utilisation efficiency. By incorporating targeted training sessions that focus on lactate threshold development, athletes can enhance their ability to utilise lactate as a fuel source during high-intensity efforts.
Recovery and Recovery: Efficient utilisation of lactate can also play a role in post-exercise recovery. Athletes who can effectively clear lactate from their system and utilise it for energy production during recovery periods may experience faster recovery times and reduced muscle soreness.
How can I use this study to improve my performance?
Nutritional Strategies: Athletes can adjust their carbohydrate intake timing and composition based on the understanding of how dietary carbohydrates are processed post-meal. Ensuring adequate carbohydrate availability before and after training or competition can optimize glycogen storage and utilization, leading to improved energy levels and performance.
Lactate Threshold Training: Understanding the role of lactate in carbohydrate metabolism can guide athletes in designing training programs to improve their lactate threshold. By training at or near their lactate threshold, athletes can enhance their ability to sustain high-intensity efforts and delay fatigue.
Recovery Practices: Incorporating strategies to support lactate clearance and carbohydrate replenishment post-exercise can aid in faster recovery and readiness for subsequent training sessions or competitions. This may include consuming carbohydrate-rich foods or beverages to replenish glycogen stores and facilitate muscle recovery.
Individualised Nutrition Plans: Athletes can work with sports nutrition professionals to develop personalised nutrition plans that consider their unique carbohydrate metabolism and lactate utilisation. Tailoring nutrition strategies to individual needs can optimise performance and support overall athletic goals.