Feb 01, 2021


Author: Prof. Diego A. Bonilla, ISAK 3

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A 4R’s approach to optimizing post-exercise recovery has been introduced: (i) Rehydration—a fundamental process that will depend on the athlete, environment and sports event; (ii) Refuel—the consumption of carbohydrates is not only important to replenish the glycogen reserves but also to contribute to the energy requirements for the immune system and tissue reparation. Several bioengineered carbohydrates were discussed but further research is needed; (iii) Repair—post-exercise ingestion of high-quality protein and creatine monohydrate benefit the tissue growth and repair; and (iv) Rest—pre-sleep nutrition has a restorative effect that facilitates the recovery of the musculoskeletal, endocrine, immune, and nervous systems. Nutritional consultancy based on the 4R’s is important for the wise stewardship of the hydration, feeding, and supplementation strategies to achieve a timely recovery. 

1. Introduction

Recovery strategies to optimize post-exercise recovery depend to a large extent on the proximity of the next session, the degree of physiological stress, and the relevance of the next event. This determines how to rehydrate, replenish energy and consume the nutrients needed to improve tissue repair. To improve comprehension regarding the nutritional strategies that impact post-exercise recovery, a mnemonic entitled the 4R’s (Rehydrate, Refuel, Repair, and Rest) is introduced. This approach divides the nutrition intervention into four interrelated scenarios that follow the post-exercise time course in order to optimize the exercise-induced adaptations and recovery (Figure 1).

2. The 4R's

2.1. Rehydrate

One of the first goals during recovery is to replace any fluid and electrolyte deficits. Most physically active individuals sweat from 0.3 to 2.4 L·h−1, which depends on exercise intensity, duration, and environmental conditions such as altitude, heat, and humidity. Moreover, individual characteristics (i.e., body mass, genetic predisposition, heat acclimatization state, physical fitness, and metabolic efficiency) might influence sweat rates for a given activity. For instance, the highest sweat rate was registered at 3.7 L·h−1 for a world-class ultramarathon runner. Thus, measuring pre and post-exercise body mass is a recommended practice to assess fluid status.

Rehydration is important, especially in team, endurance or ultra-endurance sports, where in many cases it is not possible to compensate for the loss of fluids and electrolytes that occur during exercise, particularly in hot and humid environments. As a general advise, for quick rehydration, it is recommended the consumption of 150% of the weight lost after exercise over a short recovery period (less than 4 h), with a sodium concentration between 20 and 30 mEq·L−1. Athletes and practitioners should replenish three cups of fluid per pound of weight lost (~1.5 L·kg−1) and to make sure body mass is back up before the next training session. Furthermore, it has even been shown that consuming a sodium-containing drink between 40 and 60 mEq·L−1 can improve fluid retention and rehydration when there is little time between sessions or when there is moderate dehydration.

Know more about the first R of this nutritional framework HERE.


2.2. Refuel

The second R of this framework refers to refueling. At the end of the exercise, there are several strategies to maximize muscle and liver glycogen replenishment, especially when two or more sessions are performed on the same day or when competing on consecutive days. For planning, it is necessary to consider the state of training, schedules, and the magnitude of the depletion of reserves, besides the type of exercise. In this sense, the amount of carbohydrates is determined by the need to replenish muscle glycogen stores, and according to Jeukendrup (2017), this is closely related to:

  • Time to next training session or competition,
  • Nutrition periodization to achieve adaptations,
  • Need for muscle repair and growth,
  • The amount consumed before and after as part of global requirements.

Although certain general recommendations can be given, the carbohydrate intake must be fine-tuned based on individual features, total energy daily expenditure, exercise training requirements, and the respective feedback from training performance in daily recovery. In athletes with high body mass (e.g., basketball and rugby) or players under a weight loss program it might be better to reduce the energy intake to the needs of the previous category. Additionally, resistance/power athletes do not need much carbohydrates as endurance athletes to maintain optimal liver and muscle glycogen; therefore, based on the exercise and sports nutrition review update of the International Society of Sports Nutrition, daily carbohydrate needs might be ranked as follows:

  • Moderate duration/low-intensity training (e.g., 2–3 h per day of intense exercise performed 5–6 times per week): 5–8 g·kg−1 body mass·day−1
  • Moderate to heavy endurance training (e.g., 3–6 h per day of intense training in 1–2 daily workouts for 5–6 days per week): 8–10 g·kg−1 body mass·day−1
  • Extreme exercise programs or competition (+6 h per day or high competition frequency during the week): 10–12 + g·kg−1 body mass·day−1

Know more about the second R of this nutritional framework HERE.

2.3. Repair

Scientific research has demonstrated that muscle protein synthesis (MPS) can be stimulated by either a physical allostatic challenge (e.g., resistance exercise stimulus) or by the ingestion of dietary protein, with synergistic responses when protein is consumed before and immediately after resistance exercise training. According to the International Society of Sports Nutrition position stand on nutrient timing, post-exercise ingestion (immediately to 2 h) of high-quality protein food represents a robust stimulus that impacts positively on MPS; however, similar increases in MPS have been found when high-quality proteins are ingested immediately before exercise. Indeed, taking into account the sport-specific daily needs, if an insufficient amount of protein is consumed, the athletes will develop and maintain a negative nitrogen balance, which is an indicator of protein catabolism and negatively affect recovery. Over time, this can lead to muscle wasting, injury, disease and intolerance to training. Thus, the peri-exercise ingestion of insulinotropic protein and/or essential amino acid mixtures might stimulate post-exercise net muscle protein anabolism, and this might contribute to faster tissue growth and repair. Similarly, recent findings have provided evidence that marathon runners that consume moderate amounts of protein post-exercise can have recovery benefits. With a good grade of evidence, compared to ingestion of carbohydrate alone, co-ingestion of carbohydrate plus protein together during the recovery period have resulted in no difference in the rate of muscle glycogen synthesis but it improves net protein balance.

The International Society of Sports Nutrition position stand about proteins for recovery is:

  • Optimal dose of protein for athletes to enhance MPS are dependent upon age, energy intake (higher amount is needed under energy restriction), and recent resistance exercise stimuli. Post-exercise recommendations are 0.5 g of a high-quality protein per kilogram of body mass, or an absolute dose of 40 g. Protein per meal should be between 0.25 and 0.40 g of protein per kg of body mass, or absolute values of 20 g.
  • Given the observed benefits of pre- and post-exercise protein ingestion, athletes’ tolerance should be assessed to determine the optimal time period during which to ingest protein. Notwithstanding, in spite of the anabolic effect of exercise is long-lasting (at least 24 h), athletes can take advantage of the higher muscle sensitivity to nutrient uptake after exercise due to the likely diminishment over time.

On the other hand, a large body of evidence suggests that Creatine monohydrate supplementation (0.1 g·kg−1·day−1) not only optimize exercise adaptations and increase performance but also may reduce muscle damage and/or enhance recovery from intense exercise. These effects are partially due to the optimization of the Creatine kinase (CK) system which not only serves as a spatial/temporal buffer of ATP regeneration but also leads to positive regulation of anabolic signaling pathways (such as IGF-I and MAPK) and, hence, might promote faster tissue repair and recovery. Additionally, it has been shown that chronic creatine supplementation prior to an exhaustive exercise bout and glycogen loading promotes greater glycogen resynthesis than just carbohydrate loading alone.

Continue reading about the nutritional supplements that might be use to optimize repair under this nutritional framework HERE.


2.4. Rest

There is no doubt that sleep is an absolutely vital physiological function and one of the most important factors in post-exercise recovery. It has been emphasized that naps, sleep extension, and sleep-hygiene practices seem to be advantageous to the performance by optimizing recovery. In spite of the above, von Rosen et al. (2017) reported that the recommended amount of sleep during weekdays (8 h) was not obtained by 19% of 340 Swedish adolescent elite athletes of several disciplines during the autumn semester. Moreover, athletes sleeping more than eight hours and reached the recommended nutrition intake reduced the odds of suffering a new injury. Portuguese elite female gymnasts have also found to have poor sleep habits with consequences on daytime sleepiness, sleep quality, and low energy availability associated with macro and Micronutrients’ deficiencies. In fact, according to a recent systematic review by Gupta et al., athletes show a high overall prevalence of insomnia symptoms characterized by increased sleep latency, sleep fragmentation, non-restorative sleep, and excessive daytime fatigue. Currently, there is a lack of evidence and future research should focus on conducting sleep interventions among different athlete populations to address their specific sleep demands and disturbances.

It is known that eating the right combination of foods before going to sleep and what foods to avoid in the evening may be beneficial in enhancing sleep. That is the rationale for the pre-sleep nutrition strategies, considering that several nutrients have been shown to improve sleep such as carbohydrates (high-glycemic index dinners), melatonin, tryptophan-rich protein, antioxidant-rich fruits (e.g., tart cherry juice and kiwi), and Micronutrients. Casein proteins, a type of secreted calcium (phosphate)-binding phosphoproteins, are among the most common nutrients used for pre-sleep nutrition given they are considered a high-quality protein source with high digestibility and bioavailability but with a slower digestion rate in comparison to whey. Thus, the timing of nutrient intake is as important as the composition to fulfill the nutrition needs of the athletes. Res et al. reported for the first time that casein protein ingestion immediately before sleep was not only effectively digested and absorbed but also increased MPS and net protein balance in healthy young males that performed a resistance-training bout in the evening. Moreover, it has been demonstrated that pre-sleep casein protein ingestion augments the muscle adaptive response in terms of muscle mass and strength after a 12-week resistance exercise training program in young men in comparison to placebo. Therefore, the extended window of opportunity as a result of the additive effects of resistance exercise training and protein ingestion on MPS makes the pre-sleep casein protein supplementation an effective nutrient timing strategy to optimize muscle conditioning and recovery with no need to add extra leucine. Although the positive effects of pre-sleep nutrition have been found particularly in resistance-type exercise training, more research is needed in endurance-trained athletes considering recent findings showed no improvement. The available evidence and recommendations under this new paradigm of pre-sleep nutrition are:

  • The consumption of 40–48 g of casein approximately 30 min before sleep improves post-exercise recovery and positively affect acute protein metabolism during an overnight period in healthy young adults.
  • Ashwagandha supplementation (>150 mg aqueous root extract quaque hora somni) seems to be an effective nutritional strategy to improve sleep quality in healthy male and female subjects; consequently, it should be also considered before sleep.


This entry was also published in the Scholarly Community Encyclopedia by MDPI and is a fragment of the published article:

Bonilla, D.A.; Pérez-Idárraga, A.; Odriozola-Martínez, A.; Kreider, R.B. The 4R’s Framework of Nutritional Strategies for Post-Exercise Recovery: A Review with Emphasis on New Generation of Carbohydrates. Int. J. Environ. Res. Public Health 2021, 18, 103. 


About the author:


Dynamical Business & Science Society | CEO & Board Member
MTX Corporation SPM | MTX COLLEGE Director (Europe)
Forschüng: DBSS | BioMol (UD), GICAFS (Unicordoba) & kDNA Genomics® (UPV) 
Vernetzung: ESNL (Texas A&M) | EIT Health Network | UNU-BIOLAC Network 

"Creatine in Health" Scientific Advisory Board of Creapure® - Alz-Chem Tostberg GmbH

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