Performance in endurance sports and disciplines involving intermittent efforts depends on multiple physiological factors, including carbohydrate (CHO) availability, hydration status, gastrointestinal tolerance, and appropriate regulation of the immune system. Over the last few decades, numerous studies have provided insight into how intra-training nutritional planning can optimize these responses and delay the onset of fatigue.
1. The function of carbohydrates during exercise
Carbohydrates are the primary energy source in high-intensity or long-duration exercise. Muscle glycogen and plasma glucose act as priority fuels when energy demand increases, and are key to maintaining exercise capacity.
During prolonged exercise, carbohydrate intake can:
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Maintain stable blood glucose levels.
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Attenuate muscle glycogen depletion.
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Reduce the use of amino acids as an energy source.
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Delay the onset of central fatigue through sensory stimuli in the oral cavity, even without the need to ingest them.
This combination of peripheral and central effects makes intra-training CHO intake a solid strategy for optimizing performance.
2. CHO availability and digestive tolerance
Another key aspect is gastrointestinal tolerance. Reduced blood flow to the digestive tract during exercise can cause discomfort, especially in hot conditions. However, gradual carbohydrate intake helps maintain splanchnic perfusion and reduce digestive symptoms.
The combination of carbohydrates absorbed through different intestinal transporters (for example, glucose and fructose) has been shown to:
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Increase exogenous carbohydrate oxidation.
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Allow intakes above the traditional 60 g/h.
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Reduce the risk of gastrointestinal discomfort during prolonged sessions.
These mixtures are common in long-distance sports, where intake can reach up to 90–120 g/h in athletes trained to tolerate them.
3. Hydration: more than water
Fluid losses exceeding 2–3% of body weight can reduce cardiac output, impair thermoregulation, increase perceived exertion, and compromise performance. In this context, beverages intended for exercise should take several factors into account:
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Adequate osmolarity, which promotes intestinal absorption.
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Electrolyte content, especially sodium, which is essential for maintaining blood volume and preventing hyponatremia.
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Good gastric emptying, facilitating effective hydration without digestive discomfort.
Sodium plays a decisive role by improving the absorption of water and glucose in the intestine and promoting fluid retention, while potassium contributes to neuromuscular function and fluid balance.
4. Interactions with immune function and bone health
During prolonged efforts, exercise can increase intestinal permeability and generate transient inflammatory responses. Adequate carbohydrate availability reduces the secretion of cytokines such as IL-6, modulates the redistribution of immune cells, and attenuates the impact of physiological stress.
In addition, recent research indicates that insufficient carbohydrate availability—even with adequate energy intake—can alter processes related to bone health. Maintaining a continuous supply of CHO during long-duration sessions may help minimize these effects.
5. Practical application during training
Current evidence suggests that:
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CHO intake during exercise is especially recommended after 60–90 minutes of continuous effort.
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Athletes engaging in high-intensity or very prolonged activities benefit from planned intakes of 30 to 90 g of carbohydrates per hour, or even more if they are trained to tolerate it.
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Hydration should be adjusted on an individualized basis, taking into account sweat rate, environmental conditions, and personal tolerance.
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Training the digestive system improves the ability to absorb and tolerate greater amounts of CHO and fluids during competition.
Conclusion
The scientific evidence analyzed makes it possible to understand that intra-training nutrition is an essential pillar of sports performance, especially in activities involving long duration or high intensity. This study, developed with the pioneering collaboration of Life Pro, demonstrates how science-based planning can optimize physical performance from an integrated perspective.
The results indicate that adequate carbohydrate availability during exercise not only supports metabolic processes, but also modulates the perception of fatigue, maintains energy homeostasis, and promotes better functioning of the central nervous system. Similarly, the evidence shows that the combination of multiple CHO sources—which use different intestinal transporters— increases carbohydrate oxidation per hour, improves digestive tolerance, and enhances the athlete’s ability to sustain prolonged efforts.
Hydration also emerges as a critical factor. The literature highlights that fluid losses of just 2–3% of body weight can compromise cardiac output, thermoregulation, and perceived exertion. Therefore, the use of hydration strategies that include sodium, potassium, and adequate osmolarity is essential for preserving physiological function and reducing the risk of hyponatremia.
At a systemic level, this analysis shows that carbohydrate availability modulates the immune response, reducing the secretion of inflammatory cytokines, as well as the redistribution of immune cells during prolonged exercise. In addition, recent research emphasizes that low carbohydrate availability can negatively affect bone health, even in the absence of an evident energy deficit. This underscores the importance of adequate CHO intake for maintaining the integrity of key tissues, especially in athletes subjected to high training loads.
In short, the findings highlight that intra-training nutrition should be individualized, based on scientific evidence, and adapted to the environment, the physiological demand, and the athlete’s characteristics.
In this context, the participation of Life Pro—a pioneering, innovative brand firmly grounded in science—has been essential for integrating the latest advances in physiology, sports nutrition, and performance. Its collaboration has made it possible to structure this analysis from a rigorous and up-to-date perspective, providing a solid framework for coaches, healthcare professionals, and athletes.
The conclusion is clear: a well-designed nutritional strategy makes it possible to maintain exercise intensity, delay fatigue, optimize recovery, and protect the athlete’s health in the short and long term. This knowledge is a decisive tool for addressing the challenges of modern training in endurance and high-demand sports.
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