How nutrition essentials can improve endurance performance.

By Jennifer Kurtz, PhD(c), CISSN, CSCS, EP-C

Jennifer Kurtz is an exercise physiologist with expertise in nutrition, energetics and metabolism, and sport and exercise.

Her research covers all aspects of cycling performance, ranging from power output to oxygen consumption, heart rate, perceived exertion, NO metabolite production, GI distress, and more.

Kurtz favors interdisciplinary approaches to human health-related questions, incorporating physiological approaches and nutritional methods to understand the whole-human response to exercise and nutrition, with a focus on elevating awareness of research on female athletes.

In addition to all that, she still has time to race mountain bikes (as seen above).


Endurance training is so much more than just counting carbs, and in this blog installment, Jennifer Kurtz walks us through two of the most important nutritional aspects of training: hydration and protein.

The idea that these are important isn’t new, but – as the research shows – there are better, more effective ways to approach them. Are they basic ideas? Yes. But that means it’s even more critical to get them right in order to maximize their effect on endurance performance.

Hydrating to Improve Performance

Adopting strategies to limit dehydration is critical for endurance athletes. It is commonly recommended to regularly ingest water or sports drinks (e.g., 12-16 fluid ounces every 10-15 min) with the overarching goal being to minimize the loss of body mass commonly seen because of exercising in hot and humid environments.

Though they may not be necessary to prove the point, studies do show that sports drinks during exercise can prevent dehydration and improve endurance exercise capacity. Additionally, it is important to consider the duration and intensity of the exercise for adequate hydration strategies. Frequent ingestion of water and or sports drinks is one of the most effective ergogenic aids to support thermoregulation, reduce cardiovascular strain, maintain and improve hydration, and prevent dehydration during endurance events.

The most important nutritional ergogenic aid for endurance athletes is water and limiting dehydration is one of the most effective ways to maintain exercise capacity. During endurance exercise, two problems can arise 1) disturbed fluid-electrolyte balance and 2) dehydration and overhydration.

This starts with hydration before an event, race, or exercise session. The commonly heard phrase, “once you’re thirsty you’re already dehydrated,” is indeed true; dehydration can occur even before becoming “thirsty,” so perception of thirst is not a good indicator of hydration. 

To prevent dehydration, athletes need to start drinking fluids before they become thirsty, doing so early and at regular intervals (Vitale & Getzin, 2019). However, excessive consumption of fluids is a risk factor for the development of exercise-associated hyponatremia (EAH). Hyponatremia is defined by low serum, plasma, or blood sodium concentration levels. Signs, symptoms, and effects of EAH can include dyspnea, nausea, delirium, and even death. 

The general rule of thumb for optimal pre-exercise hydration is to ingest 500 mL of water or sports drinks the night before a competition, another 500 mL upon waking, and then another 400-600 mL of cool water or sports drink 20-30 min before the onset of exercise. During exercise, to maintain fluid balance and prevent dehydration, athletes need to plan on ingesting 0.5 to 2 L/hour of fluid to offset weight loss. This requires frequent (every 10–15 min) ingestion of 12–16 fluid ounces of cold water or a sports drink during exercise (Kerksick et al., 2017).

Athletes should weigh themselves prior to and following exercise to monitor changes in fluid balance and help replace their lost fluid. During and after exercise, athletes should consume 12-16 oz of water for every pound lost during exercise to promote adequate rehydration. Additionally, sodium intake in the form of glucose-electrolyte solutions (sports drinks or hydration mixes) should be considered during the rehydration process to further promote rehydration.

Exercising in hot and humid environments requires greater attention. It takes 10-14 days to acclimatize to these types of environments, and during this time endurance athletes should drink greater amounts of fluids to make sure they meet the demands of the environment. 

Additionally, excessive weight loss techniques such as cutting weight in saunas, wearing rubber suits, severe dieting, vomiting, using diuretics, etc., are considered dangerous and are not recommended. A hydration plan is recommended to each endurance athlete and varies with sweat rates, sweat sodium content, the intensity of exercise, body temperature, ambient temperature, body weight, kidney function, and other factors (Vitale & Getzin, 2019).

Protein Intakes for Endurance Athletes

There is considerable debate surrounding how much protein an endurance athlete requires. However, current evidence indicates optimal protein intakes in the range of 1.2–2.0 g/kg/day should be considered for endurance athletes (Kerksick et al., 2017). However, ingesting higher protein quantities may be advantageous to maximize muscle protein synthesis (MPS) which is upregulated for 24 hours following exercise.

MPS is the driving force behind adaptative responses to exercise such as changes in muscle mass. Timing and dose are shown to be important; 0.25–0.3 g/kg of a quality protein source (e.g., meat, fish, poultry, eggs) in the immediate 0-2 h post-exercise provides approximately 10 grams of essential amino acids (EAA), which maximally stimulate MPS associated signaling proteins needed for protein synthesis (Vitale & Getzin, 2019). However, MPS can only be stimulated with doses of at least 3-h apart; It is recommended to spread protein doses at ~0.3 g/kg every 3-5 h to maximize MPS (Vitale & Getzin, 2019). 

The latest research shows protein ingestion may improve same-day and subsequent endurance performance, and no studies have shown that high protein ingestion hinders performance (Vitale & Getzin, 2019). Research also shows us how to ingest protein, including how much to ingest and when to ingest it.

Before exercise, it is recommended to consume 0.3 g/kg (~20-40 g) of protein with adequate EAA (~10-12 g) and leucine (~1-3 g) if tolerable. During endurance exercise, the recommended approach is approximately 0.25 g/kg protein per hour when taken along with CHOs to minimize potential muscle damage, reduce subjective feelings of muscle soreness, reduce creatine kinase elevations (a marker of muscle damage), improve MPS, and net protein balance (Kerksick et al., 2017; Vitale & Getzin, 2019). Post-exercise protein consumption added to CHOs can increase and maximize muscle glycogen synthesis by 40-100%, depending on post-CHO intake levels (Vitale & Getzin, 2019).

Protein consumption every 3-5 h throughout the day (including a dose immediately before or 0–2 h post-exercise) to a total of ~1.2–2.0 g/kg/day, may promote positive nitrogen balance, recovery, and optimally benefit endurance athletes.

Sourcing matters, too. Plant-based protein consumption is gaining attention and popularity; however, animal-sourced proteins are superior due to higher EAA content, higher leucine content, and improved digestibility kinetics to stimulate MPS.

August 01, 2023 — First Endurance

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