One critical flaw in the current paradigm is the misuse of mechanistic science to dictate actions rather than to enhance our understanding of observed outcomes. Scientists often test a specific training stimulus and, based on the mechanistic outcome, make broad declarations about what the “best” protocol or rep scheme is. This approach ignores critical variables such as training age, individual skills, the target activity or sport, overall goals, and numerous other contextual factors that influence results. For example, a study might show that a particular high-volume hypertrophy program maximally stimulates muscle protein synthesis in novice lifters, leading to claims that it is universally superior. However, when applied to advanced athletes, whose adaptive responses differ greatly from novices, the same protocol may lead to overtraining or diminished performance.
Instead, mechanistic science should be used to contextualize and better understand these empirical results, helping us refine future protocols. This approach acknowledges the inherent complexity of the human body and its adaptive responses.
When mechanistic science drives actions without empirical validation, the risk of negative outcomes increases. In contrast, when used to interpret empirical evidence, it provides valuable insights that can guide better decision-making. This distinction is crucial for developing effective strategies in health and performance.
Example: Substrate Utilization and RER in Exercise Science
A key example of the flaws in mechanism-based conclusions is the interpretation of **substrate utilization** and **Respiratory Exchange Ratio (RER)** as measures of movement economy. Traditionally, lower RER values — indicating a greater reliance on fat as fuel — are seen as a marker of improved economy and performance. However, this interpretation does not hold for **ketogenic-adapted athletes**, who primarily utilize fat for energy.
According to Noakes et al. (2023), ketogenic diets shift the exercise crossover point — the intensity at which carbohydrate becomes the primary fuel source — to much higher intensities. This metabolic shift enables keto-adapted athletes to sustain high levels of performance while predominantly burning fat, which inherently requires more oxygen for metabolism compared to carbohydrates. In this context, increased oxygen consumption does not equate to reduced efficiency. On the contrary, research has shown that keto-adapted athletes can maintain or even improve absolute work capacity despite the higher oxygen cost associated with fat metabolism.
The traditional assumption that increased oxygen consumption is inherently inefficient ignores the metabolic flexibility of keto-adapted athletes. Over time, these athletes develop an enhanced ability to oxidize fat at higher intensities, which allows them to perform sustained work without relying heavily on glycogen stores. This adaptation directly contradicts mechanistic interpretations that label higher RER values as inefficient.
Studies focusing on short-term dietary interventions fail to capture the long-term adaptations that occur with ketogenic diets. Most research on substrate utilization involves unadapted individuals, leading to erroneous conclusions about the viability of low-carbohydrate high-fat (LCHF) diets for performance. As Noakes et al. (2023) highlight, keto adaptation takes weeks to months, during which profound metabolic shifts occur. These adaptations render traditional short-term metrics like RER inadequate for assessing long-term performance outcomes in ketogenic athletes.
Broader Implications for Exercise Science
This example underscores a broader issue in exercise science, the failure to account for context and adaptation when drawing conclusions from mechanistic data. Human health and performance are dynamic and influenced by numerous factors that interact in complex ways. Reductionist models may provide useful starting points, but they cannot replace holistic, context-driven approaches that consider the adaptive nature of the human body.
In nutrition science, for instance, decades of focus on isolated nutrient impact have led to a fragmented understanding of diet and health. Public health recommendations have swung wildly — from eggs are bad, to eggs are healthy— without acknowledging the reality of impact or change that is evident in the real world. Similarly, in exercise science, the emphasis on short-term measures like RER or VO2 max fails to capture the long-term benefits of sustained adaptations, such as those seen in ketogenic athletes.
A Cautionary Note for Evaluating Recommendations
The current paradigm in health, fitness, and nutrition science is insufficient because it relies too heavily on reductionist methods and isolated mechanisms. To develop effective, lasting strategies for health and performance, researchers must adopt a more holistic approach that considers real-world complexity and long-term adaptation.
It is important for readers to critically evaluate recommendations and conclusions about improving sports performance against a comprehensive rubric. This rubric should include an understanding of what is working in real life, what has been successful for other athletes (even if it’s different than past methods), and personal experience. Broad claims based on isolated research findings often fail to account for key individual factors such as training age, skill level, specific sport requirements, and overall goals. By applying a context-driven evaluation process, athletes and coaches can avoid common pitfalls and make informed decisions tailored to their unique needs.
Reference:
Noakes et al. (2023), “Low carbohydrate high fat ketogenic diets on the exercise crossover point and glucose homeostasis,” Frontiers in Physiology, Volume 14, DOI: 10.3389/fphys.2023.1150265.
