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Food Timing

 
By: NCSF  on:  Jul 28 2015
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The recreational fitness enthusiast would do well to regulate macronutrient intake to quantities that support their activity levels. They should consume lower quantities of processed carbohydrates and create meals in a mixture and manner that best serves recovery needs while supporting daily energy demands. Small mixed meals (carbohydrate-protein-fat) throughout the day generally provide nutritional adequacy for this group. For those who engage in high-intensity exercise or compete in athletic events, particularly where the training is continuous in nature, there exists a different challenge as it relates to macronutrient management. Recovery from intense exercise must account for higher levels of muscle tension, greater glycogen depletion and (consequently) greater fluid loss. Without adequate energy provisions or consumption at proper time intervals an athlete can run the risk of delayed recovery, performance decline, muscle damage and even injury. Low energy provisions, inadequate fluid balance and training-induced hypoxia collectively cause significant muscle disruption and potential damage. Therefore, if intense training is performed throughout a week, nutrient quantities and timing must reflect the duration and type of stress experienced to ensure recovery. If this is not properly managed the athlete will run a much greater risk for experiencing the symptoms of overtraining syndrome.

Contemporary training for anaerobic sports, as well as high-intensity fitness training, involves diverse routines that place a wide array of physiological demands on the participant. This requires a multi-faceted nutritional strategy to support general training needs, which should to be tailored to each training phase, as well as competition if part of the equation. Anaerobic sport athletes experience high training intensities and volumes for most of the season, so energy intake must be sufficient to support recovery and adaptations. The specificity of the training should reflect the provisions consumed for recovery.

With this said, a nutritional plan should reflect three key elements:

  • Adequate glycogen storage for training and competition
  • Adequate total caloric/energy intake
  • Proper nutrient balance for optimized recovery

Splitting nutritional intake into specific roles is a common theme amongst sports nutritionists. There exists pre-training nutrition, during-event nutrition and post-event nutrition guidelines. “Old school” methodology was based on the calories in – calorie out concept, but today we know that energy timing and the metabolic impact of specific nutrients have greater implications for energy storage and adaptation support. For instance, protein intake, depending on timing, quantity and type, may support protein synthesis in trained tissue, glycogen synthesis in the liver or lead to lipid (body fat) synthesis. In most cases, it is the internal metabolic environment that dictates the outcome for ingested macronutrients, which underscores the relevance of nutrient timing.

Pre-training

Low pre-exercise muscle glycogen reduces high-intensity performance, so daily carbohydrate intake must be emphasized throughout all phases of training and competition. Many people erroneously believe what is consumed in the last meal before the workout has the greatest impact on muscle glycogen stores during the workout - this is not correct and has major implications. In actuality, what is consumed after the workout, training bout, or event has the greatest influence on a muscle’s glycogen content. Pre-activity food plays a limited role in muscle glycogen content but a larger role in blood glucose levels as well as hepatic glycogen stores. So, a feeding 1-2 hours before a workout is more related to central processes than peripheral glycogen saturation. In most cases, studies that have yielded the greatest results from pre-activity feeding are based on assessments during endurance events. Recent studies though support moderate carbohydrates just before activity. When the influence of timing of pre-exercise carbohydrate feeding and carbohydrate concentration was analyzed on short-duration, high-intensity exercise capacity, there were some advantages. Exercisers who ingested a 6.4% carbohydrate/electrolyte sports drink 30 minutes before exercise yielded limited improvements. Higher levels of carbohydrate were not beneficial; actually hindering performance with a 12% solution. This suggests a person drinking a Gatorade before a workout will not experience the consequences of sugar digestion/metabolism during anaerobic activity, but a person drinking a coke would likely see a performance decline related to anaerobic high-intensity activity.

For endurance athletes the timing and composition of the pre-exercise meal is a more significant consideration for optimizing metabolism and performance. Interestingly, despite increasing insulin levels and reduced fat oxidation during prolonged training, carbohydrate feedings prior to endurance exercise are common and have generally been shown to enhance performance. The literature suggests that the negative metabolic effects may be attenuated by consuming low-glycemic index carbohydrates before exercise. High-fat meals have also been experimented with as a pre-event macronutrient strategy. While they seem to have beneficial metabolic effects (e.g., increased fat oxidation and possible sparing of muscle glycogen) these effects do not translate into enhanced performance - and actually can be ergolytic for mid-to-long distance events. Protein is commonly consumed by body builders and recreational lifters during resistance training bouts, but less is conclusively known about its impact when consumed in a pre-exercise meal. While limited research exists on pre-exercise protein consumption and subsequent performance, some evidence suggests the potential for enhanced pre-exercise glycogen synthesis and metabolic benefits during the bout when small quantities are consumed directly prior. A 2007 article suggested that when complete proteins are ingested before resistance training, the response of muscle anabolism was greater than consumption occurring 0-3 hours after exercise. The author’s explanation for the superior response of pre-exercise protein ingestion was increased delivery of amino acids to the working muscles.

Nutrition during exercise

During any exercise the main fuel to provide an advantage is carbohydrates. It has been well-established that carbohydrate ingestion during prolonged (>2 hours) moderate-to-high intensity exercise can significantly improve endurance performance. Although the precise mechanism(s) responsible for the ergogenic effects are still unclear, they are likely related to the sparing of skeletal muscle glycogen, prevention of liver glycogen depletion (and the subsequent development of hypoglycemia), and/or allowing high rates of carbohydrate oxidation. Currently, for prolonged exercise lasting 2-3 hours, athletes are advised to ingest 60 grams of carbohydrate per hour (g·h⁻¹) at a rate of ~1.0-1.1 gram per minute (g·min⁻¹) to allow for maximal glucose oxidation rates. However, well-trained endurance athletes competing longer than 2.5 hours can metabolize carbohydrates at rates up to 90 g·h⁻¹ (~1.5-1.8 g·min⁻¹), provided that multiple transportable forms are ingested (e.g., glucose, fructose, maltodextrins). Surprisingly, small amounts of carbohydrate during exercise may also enhance the performance of shorter (45-60 min), more intense exercise bouts despite the fact that carbohydrate stores are unlikely to be limiting. Carbohydrates ingested during the exercise bout, often as an electrolyte solution, aid anaerobic exercise activity performance as well as athletes involved in intermittent or team sports. The mechanism(s) responsible for such ergogenic properties during short, more intense exercise bouts has been suggested to reside in the central nervous system. Protein ingested during exercise is also theorized to aid in circulating amino acid pools, which support liver glycogen during endurance activity - but will not contribute to energy contribution to any significant value. In fact, a literature review suggests protein supplements provided no further ergogenic effect above carbohydrate supplementation when carbohydrates are delivered at optimal rates during exercise. In addition, the limited data available suggests neither the recovery of muscle glycogen stores nor the rate of utilization during exercise is related to any ergogenic effect of additional protein supplements. Therefore, if carbohydrates are available protein is not necessary.

Post-exercise nutrition

Following exercise/training seems to be the key time to optimize adaptations and restore glycogen for subsequent performance bouts. Carbohydrates are by far the most relevant nutrient at this time. Carbohydrate should be ingested as early as possible in the post-exercise period and at frequent intervals during recovery to maximize the rate of muscle glycogen resynthesis. While any high-glycemic carbohydrate will work (1g/min/hour) there may be some benefit by adding whey protein at a 3carbohydrate-1protein ratio. Adding ≥0.3 g/kg/h of protein to a carbohydrate supplement results in a synergistic increase in insulin secretion that can, in some circumstances, accelerate muscle glycogen resynthesis. The added protein may also aid in improving recovery for endogenous protein-based tissues. Again while carbohydrates alone are satisfactory, when are not ingested in quantities sufficient to maximize the rate of muscle glycogen resynthesis, the inclusion of protein may at least partially compensate for the limited availability of optimal fuel. Some studies have reported improved physical performance with ingestion of carbohydrate-protein mixtures, both during exercise and recovery, based on subsequent exercise testing. Clearly, the potential for improved performance associated with the added protein supplement exists under certain conditions. Specifically, if the additional protein increases the energy content of a supplement to optimal levels and/or the provisional carbohydrate composition is below the recommended rate, the added caloric density and insulin response associated with the complete proteins will be beneficial. While it seems the underlying mechanism for positive effects is at least partly due to increased muscle glycogen resynthesis, some have proposed other factors but with less support. These include an increased central drive for exercise, a blunting of exercise-induced muscle damage, altered metabolism during exercise subsequent to recovery, or a combination of these mechanisms.

Likely the biggest misconception is to consume protein alone following exercise. Certainly 20-30 g is warranted to promote protein uptake/synthesis but carbohydrates should be used for nutrient recovery. Several studies looked at protein supplementation following a bout of exercise, but provide no support that it attenuates muscle soreness and/or lowers markers of muscle damage, as theorized above. In fact, muscle glycogen content (or lack of) is more related to muscle damage during exercise than total protein intake. Data does suggest potential ergogenic effects associated with protein supplementation when participants are in a negative nitrogen and/or energy balance. From this data it should be understood that carbohydrates should be consumed at a level that completely restores the quantity of glycogen depletion; while proteins, at least post-exercise, can be consumed at lower quantities to encourage protein synthesis. A basic rule is to consume the total caloric expenditure in timely meals over the 3-4 hours of recovery, starting immediately at the point of training/practice cessation.

 
Comments
 
 
 
Carmen Bruno
Date: Nov 16 2015 3:36 PM
 
 
I'm curious as to what research papers or studies this 3:1 ratio is being sourced. The NCSF CPT Textbook does not mention this in the Nutrition and Supplement chapters. However, this is mentioned in the "Advanced Concepts of Personal Training Reference Guide" that will be used in the hands-on workshop in NYC, December 5-6, on page 35, but no source in the textbook is provided. There is one other place in the study materials, perhaps one of the practice exams where this is mentioned, but I cannot locate it at the moment. I google searched this topic and many hits were found recommending a 2:1 or 4:1 ration of CHO:Protein. Thanks, Carmen Bruno CPT Id: 2717734
 
 
 
Junior Leoso
Date: Aug 2 2015 1:24 PM
 
 
Great articles here. Thanks so much for the solid content
 
 
 
 
 
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