Nutrient Timing for Optimal Performance in Aerobic Endurance

This chapter explores the significance of timed nutrient administration in facilitating physiological adaptations to exercise and enhancing overall health and performance. It emphasizes the dynamic nature of nutrient timing, considering variations in athlete demands related to travel, competition, and training throughout the year. The goal is to provide athletes and coaches with a comprehensive understanding of energy, macronutrient, fluid, and micronutrient consumption to formulate an effective nutrition plan.

Scientific Foundation: The chapter delves into a step-by-step breakdown of nutritional considerations supported by scientific literature. It focuses on when to consume specific foods or supplements, drawing on numerous research studies that highlight the impact of timed ingestion of macronutrients and amino acids on adaptive responses to exercise. The spectrum of responses includes improved glycogen resynthesis, maintenance of blood-based fuels, enhanced performance, muscle growth, body composition, immune system functioning, and mood improvements.

Historical Context: Tracing the historical evolution of nutrient timing, the text begins with the early consideration of carbohydrate intake before or during exercise, noting instances such as sugary snacks consumed before the 1928 Olympic marathon. The chapter highlights the emergence of carbohydrate loading in the 1960s and its impact on increasing carbohydrate storage in the liver and muscles, thereby sustaining glucose levels during prolonged exercise.

Expanded Scope: The narrative moves beyond historical practices to recent research, exploring the pre exercise ingestion of not only carbohydrates but also amino acids, protein, and creatine. This expanded scope considers the substances’ potential to stimulate exercise training adaptations and prevent muscle tissue breakdown. Notable studies are referenced, offering insights into the evolving landscape of nutrient timing.

Nutrient Timing and Aerobic Endurance Performance: A substantial portion of the chapter is dedicated to the role of nutrient timing in aerobic endurance performance. It underscores the body’s reliance on carbohydrate, fat, and protein as fuel sources during exercise, emphasizing the limited supply of carbohydrate in muscles and the consequences of its depletion during prolonged, moderate- to high-intensity exercise. The section introduces the concept of V . O2max, highlighting its significance in assessing fitness levels.

Glycogen Management: Managing glycogen levels becomes a focal point, with recommendations for carbohydrate intake and caloric distribution. The text explores strategies to sustain glycogen levels and outlines challenges, such as inadequate carbohydrate consumption by some athletes. Strategies for quick glycogen restoration are presented as a solution, recognizing the importance of tailored approaches based on individual dietary habits.

Carbohydrate Loading and Pre-Exercise Strategies for Aerobic Endurance

Carbohydrate Loading: Carbohydrate loading, a practice embraced by athletes, involves saturating muscle glycogen stores before prolonged events leading to glycogen depletion. The historical approach, involving a depletion phase followed by high-carbohydrate intake, demonstrated improved training endurance. Recent studies on well-trained runners propose a more practical method, suggesting that reducing exercise volume coupled with a high-carbohydrate diet over three days can elevate glycogen levels significantly.

Nutrient Intake Before Aerobic Endurance Exercise: The chapter underscores the importance of nutrient intake before aerobic endurance exercise, divided into two phases: 2 to 4 hours pre exercise and 30 to 60 minutes pre exercise. Research suggests that single carbohydrate feedings during these phases enhance muscle glycogen levels and blood glucose maintenance, although their impact on performance remains equivocal. Emphasizing high-carbohydrate meals or snacks, especially in fasting situations or after poor recovery efforts, is recommended for optimal carbohydrate utilization.

Glycogen Management: Efficient glycogen management is crucial, with the text recommending a carbohydrate-rich meal (1 to 4 g/kg body mass) several hours before exercise. For early morning exercises, a PR exercise high-carbohydrate meal 2 to 4 hours prior becomes vital to counter reduced liver glycogen from overnight fasting. Practical considerations, such as balancing fueling and sleep, are discussed, with an acknowledgment of the need for individualized approaches to avoid gastrointestinal distress.

Carbohydrate Source Controversy: Controversies surrounding carbohydrate ingestion before exercise are explored, particularly regarding the type of carbohydrate. While ingestion of carbohydrate elevates insulin levels and improves glucose uptake, concerns about hypoglycemic responses persist anecdotally. Studies indicate that providing carbohydrate within 60 minutes before exercise has no negative impact and may enhance performance. The glycemic index’s influence on performance, once considered crucial, is debunked, with fructose ingestion cautioned against due to potential gastrointestinal distress.

Enhancing Aerobic Endurance: Nutrient Intake Strategies During Exercise

The chapter focuses on nutrient considerations during aerobic endurance exercise, primarily delving into the role of carbohydrate administration and its impact on performance, glycogen management, and metabolic adaptations. Research efforts over time have evolved from emphasizing blood glucose maintenance to exploring mixed carbohydrate sources and amino acid additions for recovery and muscle damage monitoring.

Providing Carbohydrate During Exercise: While there are debates about potential negative metabolic consequences of carbohydrate ingestion before or during exercise, the majority of studies support the idea that carbohydrate intake improves or sustains performance. The text discusses the high metabolic demand for carbohydrates during exercise, with considerations on slowing down muscle glycogen breakdown and the biochemistry supporting the performance benefits of carbohydrate ingestion.

Carbohydrate Oxidation Rate: The chapter explores the concept of carbohydrate oxidation rate, establishing a peak rate during prolonged moderate-intensity exercise. The research by Asker Jeetendra’s group investigates the impact of mixing different carbohydrate forms to increase oxidation rates. Studies reveal enhanced rates with carbohydrate mixtures, demonstrating the potential benefits of diverse carbohydrate sources during exercise, with examples like glucose and sucrose or maltodextrin and fructose.

Frequency and Timing of Carbohydrate Intake: Addressing the frequency and timing of carbohydrate intake during exercise, the text presents studies indicating improved performance with more frequent carbohydrate feedings. Investigations by Fielding et al. (1985) and McConell et al. (1999) highlight the positive influence of frequent carbohydrate supplementation on blood glucose levels, endurance, and time-trial performance during extended exercise sessions. The importance of continued carbohydrate intake throughout exercise is emphasized.

Influence of Baseline Glycogen Levels: The chapter discusses the impact of baseline glycogen levels before exercise, drawing from studies by Widrick et al. (1993) and others. Findings underscore the significance of carbohydrate delivery during exercise, particularly when muscle glycogen levels are low at the beginning of prolonged exercise bouts. Baseline glycogen levels emerge as a crucial factor influencing the effectiveness of carbohydrate administration during exercise.

Performance Enhancement and Carbohydrate Delivery: The concluding section highlights the substantial body of research supporting the positive impact of carbohydrate ingestion during exercise. Studies on prolonged exercise at moderate intensity and high-intensity intermittent activities demonstrate that carbohydrate intake sustains blood glucose levels, spares glycogen, and contributes to enhanced performance. The text acknowledges the wealth of literature supporting these findings and references comprehensive reviews for readers seeking detailed insights into the topic.

Carbohydrate and Protein Synergy in Aerobic Endurance Exercise

The chapter explores recent developments in the integration of protein with carbohydrate supplementation during aerobic endurance exercise. While this field of study is relatively new, initial findings suggest that the combined intake of protein or amino acids alongside carbohydrates could potentially enhance performance, aid in recovery, and mitigate muscle damage associated with prolonged exercise.

Performance Enhancement and Protein Inclusion: The text delves into a pivotal study where participants underwent 3 hours of cycling at varying intensities, followed by a time-to-exhaustion trial. The participants consumed either a placebo, a 7.75% carbohydrate solution, or a 7.75% carbohydrate + 1.94% protein solution during each session. Results revealed that while the carbohydrate group showed improved time to exhaustion compared to the placebo, the addition of protein resulted in even greater performance gains.

Mitigating Muscle Damage with Carbohydrate-Protein Combination: Saunders and colleagues (2004) conducted a study focusing on the impact of ingesting a carbohydrate + protein combination during exhaustive exercise bouts. Cyclists ingested either a 7.3% carbohydrate solution or a 7.3% carbohydrate + 1.8% protein solution every 15 minutes during two exhaustive exercise sessions. The carbohydrate + protein group exhibited a remarkable 29% increase in performance after the first bout and a 40% increase after the second bout. Additionally, markers of muscle damage were significantly lower, emphasizing the potential of the carbohydrate + protein combination to attenuate exercise-induced muscle damage .

Consistency in Performance Benefits: The chapter discusses the consistency of performance benefits observed in subsequent studies. A 2007 study by the same group, employing a gel composition of the carbohydrate + protein combination, replicated the positive outcomes seen with the liquid solution. Another study in 2004 investigated ultra-endurance athletes, comparing the impact of consuming carbohydrate alone versus a carbohydrate + protein combination after 6 hours of aerobic endurance exercise. The combined intake resulted in improved net protein balance during exercise and post-exercise recovery, highlighting the potential of this combination to positively influence protein turnover and recovery.

Understanding Protein Balance: The text introduces key concepts such as protein balance, breakdown, and synthesis, providing a comprehensive understanding of how the combination of protein and carbohydrate influences these processes. Definitions clarify the roles of protein breakdown and synthesis, with a focus on muscle protein synthesis in the context of exercise and nutrition literature.

Nutrient Timing Strategies for Optimal Recovery in Athletes

The chapter focuses on postexercise nutrient timing, a predominant theme in scientific literature. It explores how nutritional strategies, particularly the timing of nutrient intake, can optimize recovery processes. The text highlights the significance of maintaining maximal glycogen levels and delves into studies examining the impact of postexercise nutrient intake on muscle protein balance and adaptations in resistance training.

Carbohydrate and Glycogen Resynthesis: The recovery and maintenance of muscle glycogen emerge as critical considerations for athletes across various disciplines. A consistent finding in the literature underscores the importance of ingesting 1.5 g carbohydrate per kilogram body weight within 30 minutes post-exercise for enhanced muscle glycogen resynthesis. The role of insulin sensitivity and the impact of different forms of carbohydrates, with a caution against high fructose levels, are discussed. The text emphasizes the rapid decline in glycogen resynthesis by delaying carbohydrate ingestion by just 2 hours.

Strategies for Glycogen Depletion: In cases of glycogen depletion resulting from prolonged or high-intensity exercise, the text outlines an aggressive carbohydrate administration regimen. Recommendations include a carbohydrate intake of 0.6 to 1.0 g/kg body weight per hour during the first 30 minutes post-exercise, followed by identical doses every 2 hours for the next 4 to 6 hours. Alternative strategies, such as more aggressive approaches involving 1.2 g carbohydrate per kilogram body weight per hour, are explored for maximizing glycogen resynthesis rates over an extended period.

Practical Considerations for Athletes: The practicality of immediate recovery needs is discussed in the context of athletes engaged in activities with follow-up performances within 2 to 4 hours. Findings suggest that frequent feedings of high-carbohydrate meals over 4 to 6 hours post-exercise can achieve maximal muscle glycogen levels. The text also highlights the importance of optimal dietary carbohydrate levels (around 8 g/kg body weight per day) and the potential impact of carbohydrate intake on inflammatory or proteolytic cascades that may affect recovery.

Carbohydrate With Protein and Glycogen Resynthesis: The integration of protein with carbohydrate becomes a focal point, with studies suggesting its potential to enhance muscle glycogen recovery and attenuate muscle damage. Studies, such as one conducted by Ivy and colleagues (2002), emphasize the effectiveness of a carbohydrate + protein + fat supplement in promoting greater restoration of muscle glycogen, attributed to a heightened insulin response. However, the universal acceptance of this guideline remains under discussion.

Studies on Carbohydrate and Protein Combination: Studies by Berardi and Tarnopolsky and their respective teams contribute to the discussion by comparing the impact of carbohydrate + protein versus carbohydrate-only ingestion post-exercise. Results indicate that the carbohydrate + protein combination not only increases muscle glycogen but also enhances performance and work output. The potential influence of essential amino acids, especially branched-chain amino acids, on optimizing protein and glycogen synthesis after exercise is explored.

Nutrient Timing Impact on Resistance Training, Strength, and Power Performance

This segment delves into the evolving research landscape exploring the effects of nutrient timing, specifically the provision of carbohydrates and proteins, during resistance exercise. The focus extends to how these nutritional strategies influence muscle protein balance, hormonal changes, recovery from muscle damage, and the modulation of strength and performance. As the body of knowledge rapidly expands, nutrient timing emerges as a crucial factor in enhancing adaptations to resistance training for athletes pursuing gains in strength, power, or size, irrespective of gender or age.

Nutrient Intake Before and After Resistance Training: Traditionally centered on pre-exercise carbohydrate delivery, recent research has shifted to explore the potential benefits of ingesting protein or amino acids, sometimes combined with carbohydrates, before resistance exercise. Studies, such as one by Tipton and colleagues (2001), indicate that a combination of carbohydrate and essential amino acids immediately before resistance training can significantly increase muscle protein synthesis. Findings also suggest that pre or post-exercise ingestion of whey protein, irrespective of timing, can enhance the rate of muscle protein synthesis. Notably, combining essential amino acids with a carbohydrate source pre-exercise may yield superior results than post-exercise ingestion.

Multicurrent Compound Impact on Performance: The text introduces a study by Kraemer and colleagues (2007) demonstrating that pre-exercise ingestion of a multicurrent compound, including creatine, caffeine, and arginine, significantly improved vertical jump power and repetitions performed at 80% 1RM during resistance training. The study suggests a potential modulatory effect on performance, muscle hypertrophy, and hormonal levels linked to training adaptations.

Longer-Duration Studies and Resistance Training Adaptations: The narrative emphasizes the practical significance of longer-duration studies (8-12 weeks) incorporating heavy resistance training programs alongside nutrient timing. Studies, such as one conducted by Coburn and colleagues (2006), reveal that pre-exercise supplementation of whey protein and leucine results in greater increases in maximal strength over a six-week period compared to carbohydrate alone. Further research by Candow and Willoughby and their teams reinforces the association of protein and carbohydrate supplementation before and after resistance exercise with improvements in strength, lean mass, body fat percentage, anabolic hormone levels, and muscle hypertrophy markers.

Nutrient Timing Over Weeks of Supplementation and Training: Cribb and Hayes (2006) investigate the impact of nutrient timing strategies over several weeks, demonstrating significantly greater increases in lean body mass, 1RM strength, Type II muscle fiber cross-sectional area, muscle creatine, and glycogen levels when supplements containing protein, creatine, and carbohydrate are consumed immediately before and after workouts. The narrative highlights the potential for consistent supplementation and effective training programs to contribute to better long-term performance.

Follow-Up Studies and Considerations: Follow-up studies, like the one by Hoffman and colleagues (2009), provide additional insights. Participants ingesting a protein source before and after workouts over several weeks showed no significant difference in strength, power, or body composition based on timing strategies, suggesting the importance of protein intake levels and the absence of carbohydrates in the supplementation regimen.

Amino Acid Ingestion and Muscle Protein Synthesis: The section concludes by summarizing the impact of amino acid or whole protein source ingestion within 30 minutes before resistance training on significantly increased muscle protein synthesis. The narrative acknowledges the variation in protein sources, emphasizing that soy protein may not be as effective for muscle hypertrophy as milk proteins. Prolonged studies spanning weeks consistently demonstrate improvements in various parameters, reinforcing the role of nutrient timing in achieving gains in body mass, lean mass, body fat percentage, strength, and myofibrillar content.

Optimizing Performance and Recovery

This segment delves into the limited yet significant body of research exploring the impact of nutrient intake during resistance training or strength and power events. Drawing parallels with aerobic endurance exercise studies, the data suggests that providing carbohydrates, or a combination of carbohydrates and proteins, may offer benefits such as sustaining muscle glycogen, preventing cortisol increases and markers of muscle breakdown, and promoting muscle hypertrophy.

Carbohydrate Ingestion and Muscle Glycogen: Haff and colleagues (2000) conducted a pivotal study involving resistance-trained males ingesting carbohydrates before and during lower body resistance training. The results indicated a 49% increase in muscle glycogen levels with carbohydrate intake compared to a noncaloric placebo. This early research shed light on the potential significance of carbohydrate provision during resistance exercise, hinting at its role in promoting recovery and facilitating a higher training volume.

Carbohydrate + Protein Combination and Protein Breakdown: Subsequent studies by Bird, Tarpenning, and Marino explored the impact of a carbohydrate + protein combination during resistance exercise on protein degradation. Participants consuming this combination experienced significantly lower blood cortisol levels (a marker of protein breakdown) compared to the placebo group. Further analysis of urinary markers of muscle protein breakdown supported the efficacy of the carbohydrate + essential amino acid combination in mitigating protein degradation during resistance exercise.

Cumulative Effects Over Weeks of Training: Extending the investigation to a 12-week period, Bird and colleagues observed the cumulative effects of ingesting a carbohydrate + essential amino acid combination during regular resistance training. This prolonged study revealed a 26% decrease in protein breakdown, marked increases in muscle cross-sectional area, and significant growth in the size of muscle fibers. The authors concluded that consistent ingestion of this combination optimizes the balance between muscle growth and loss during resistance training.

Support for Nutrient Intake Strategies: Overall, the collective research suggests that nutrient intake strategies, including carbohydrate alone or a combination of carbohydrate + protein, during resistance training may contribute to increased muscle glycogen levels, enhanced muscle cross-sectional area, and decreased protein breakdown. Findings from Haff et al. (2000) and Bird, Tarpenning, and Marino (2006a, 2006b, 2006c) align in highlighting the potential benefits of strategic nutrient provision during resistance exercise.

Considerations for Athletes: The text emphasizes the importance of cautious implementation, especially during competition or events, due to potential gastrointestinal upset from new foods or supplements. It underscores the necessity for athletes to test any supplementation strategy in a practice situation that simulates competition to avoid hampering performance with untested elements during crucial events. This precautionary approach ensures that athletes can benefit from the research-backed nutrient intake strategies without compromising their performance due to unforeseen reactions.

Post training Nutrition and Protein Balance: 

This section explores the intricate dynamics of post training nutrition and its crucial role in managing protein balance, particularly after resistance training. Initial insights reveal that a single bout of resistance training elicits both protein synthesis and breakdown, resulting in an overall negative protein balance in untrained individuals. However, as training progresses, this balance gradually shifts, reaching a neutral state after acute resistance training sessions.

Amino Acid Provision for Protein Synthesis: Studies, including those by Phillips et al. (1999) and Pitkanen et al. (2003), establish that providing amino acids through infusion or ingestion as a dietary supplement, snack, or meal increases plasma amino acid concentrations at rest or after resistance exercise. The combination of a modest protein supply (6 to 12 g essential amino acids) with a carbohydrate source (20 to 40 g) post-exercise has shown to enhance protein synthesis significantly. Notably, the immediate postexercise period is pivotal for remarkable increases in muscle protein synthesis, emphasizing the importance of considering this timeframe for nutrient intake.

Carbohydrate and Protein Combination After Exercise: While a large dose of carbohydrate (100 g) 1 hour after intense lower body resistance training yields marginal improvements in protein balance, it is not deemed detrimental. However, it falls short of being the ideal nutrient in isolation for post-resistance exercise consumption. Carbohydrate’s inclusion is vital for stimulating glycogen resynthesis and enhancing palatability. The text underlines the primary interest in delivering free amino acids, particularly essential amino acids, in dosages ranging from 6 to 40 g, consistently demonstrating their ability to stimulate muscle protein synthesis.

Timing and Impact of Amino Acid Ingestion: The optimal timing for amino acid supplementation after resistance training remains undetermined, with varying studies suggesting immediate, 1 hour, 2 hours, or 3 hours post-exercise windows. Regardless of the specific timeframe, amino acid provision during the postexercise period consistently increases muscle protein synthesis, as indicated by studies such as those by Borsheim et al. (2002), Ivy et al. (2002), and Tipton et al. (1999b, 2001). The text emphasizes the absence of a universal recommendation regarding the dosage and ratio of essential amino acids and carbohydrates to maximize protein balance.

Impact of Different Protein Types and Dosages: Numerous studies have investigated the impact of protein types and dosages on muscle protein balance after resistance exercise. While optimal dosages remain uncertain, the general consensus is the ingestion of some form of nutrients within 2 hours post-exercise. The widely accepted guideline suggests a carbohydrate + protein combination in a 4:1 carbohydrate-to-protein ratio during this timeframe. This translates to ingesting 1.2 to 1.5 g carbohydrate per kilogram body weight and 0.3 to 0.5 g essential amino acids or whole protein per kilogram body weight.

Post training Supplementation and Training Adaptations: Maximizing Strength and Body Composition Changes

This section delves into the realm of post training supplementation and its impact on training adaptations, with a focus on optimizing strength and body composition changes. While acknowledging the crucial role of muscle glycogen restoration and immediate changes in muscle protein synthesis during resistance training, the text emphasizes the varying importance of these factors for athletes engaged in different types of training.

Combinations of Carbohydrate and Protein: Research endeavors have explored the effects of different combinations of carbohydrate and protein after each exercise bout during resistance training over several weeks. Numerous studies, including those by Candow et al. (2006), Cribb and Hayes (2006), Kerksick et al. (2006, 2007), and others, demonstrate diverse individual results. However, the collective findings consistently support the rationale for postexercise administration of carbohydrate and protein to facilitate improvements in body composition and strength. Figures 9.7 and 9.8 illustrate the changes observed in body composition and strength performance from one such study, reinforcing the positive outcomes of postexercise supplementation.

Whey and Casein Protein Sources: Drawing parallels with carbohydrate, researchers have investigated the impact of various protein sources on digestive and amino acid kinetics, as well as resistance training adaptations. Distinct properties of whey and casein proteins have been explored by French researchers, revealing that whey protein is absorbed into the bloodstream at a significantly greater rate than casein protein. While whey protein demonstrates a pronounced effect on increasing protein synthesis, casein protein appears effective in preventing muscle tissue breakdown. Comparative studies highlight whey protein’s superior essential amino acid content, contributing to its favorability. Research by Wilkinson and colleagues (2007) and Kerksick et al. (2006, 2007) further solidifies the benefits of milk protein sources, emphasizing their potential to enhance net muscle protein accretion, protein balance, and lean mass gains.

Creatine Supplementation: The incorporation of creatine monohydrate into carbohydrate + protein combinations has been explored in subjects participating in regular resistance training programs. Creatine, a well-researched dietary supplement known for enhancing performance and training adaptations, has yielded mixed results in various studies. Tarnopolsky and colleagues (2001) reported significantly greater gains in body mass with creatine + carbohydrate compared to protein + carbohydrate. Conversely, studies by Cribb and colleagues (2007) found no differences with the addition of creatine to the supplement. Nevertheless, other studies, including those by Cribb, Williams, and Hayes (2007) and Kerksick et al. (2007), indicate that adding creatine monohydrate to a postexercise regimen of carbohydrate and protein can maximally stimulate improvements in strength and body composition.