Post-Exercise Nutrition & Supplementation: Research Update!

This is an investigation into the metabolic responses of high-glycemic or low-glycemic meals consumed during recovery from prolonged exercise. This is a good read if you are prepared for some technical jargon.
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Carbs & Recovery

Traditionally, it's been recommended that athletes ingest high-glycemic carbs (e.g., sugars, white bread) after exercise. High-glycemic carbs are broken down easily and increase rapidly the flow of glucose into the bloodstream. This glucose can then be converted to glycogen in your muscles ("filling your tank"). Unfortunately, high-glycemic carbs increase risk of obesity, diabetes and heart disease.

A recent study by Dr. Stevenson and co-workers investigated the metabolic responses to high-glycemic or low-glycemic meals consumed during recovery from prolonged exercise. Meals were provided 30 minutes and two hours following cessation of exercise. The authors concluded,

"The glycemic index of the carbohydrates consumed during the immediate post-exercise period might not be important as long as sufficient carbohydrate is consumed."

Although endurance athletes may benefit from high-glycemic carbs, bodybuilders and other strength-power athletes should eat mainly low- and moderate-glycemic carbs such as unprocessed whole grains, fruits and legumes.

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Protein Hydrolysates & Recovery

We Have Four Ways To Get Amino Acids Into The Blood:

  1. Whole food proteins
  2. Intact protein supplements
  3. Free form amino acids
  4. Protein hydrolysates

Protein can be hydrolyzed, producing small chains of amino acids called peptides. This process mimics our own digestive actions thus making it an ideal way to process protein.

Protein Or Peptide?
Peptides differ from proteins, which are also long chains of amino acids, by virtue of their size. Traditionally, those peptide chains that are short enough to make synthetically from the constituent amino acids are called peptides rather than proteins.

The informal dividing line is at approximately 50 amino acids in length (some people claim shorter lengths), since naturally-occurring proteins tend, at their smallest, to be hundreds of residues long. So, in essence, a peptide is a small protein.

There is considerable movement to redefine this arbitrary distinction such that a peptide is an amino acid molecule without structure; on gaining defined structure it is a protein.

Thus the same molecule can be either a peptide or a protein depending on its environment; though there are often peptides which cannot be proteins.

Several studies have shown that protein hydrolysates containing mostly di- and tri-peptides are absorbed more rapidly than free form amino acids and much more rapidly than intact proteins. Obviously, this is a desirable trait for serious athletes who wish to maximize amino acid delivery to muscle.

Van Loon Study:

    In a recent well-controlled study by Dr. van Loon and colleagues, a total of 10 drinks were tested in eight non-obese males after an overnight fast to investigate the insulinotropic (stimulating the production of insulin) potential of several free amino acids, protein hydrolysates, and an intact protein.

    At zero, 30, 60, and 90 minutes, the subjects received a beverage 3.5 mL/kg to ensure a given dose of 0.8 g/kg carbohydrate (50 percent as glucose and 50 percent as maltodextrin) and 0.4 g/kg of an amino acid and protein hydrolysate mixture every hour.

    The results of this study indicate that oral ingestion of some amino acid mixtures in combination with carbohydrates can produce strong insulinotropic effects.

    Hydrolysates Vs. Intact Proteins:

      To compare the insulinotropic effect of the ingestion of the protein hydrolysates with that of an intact protein, sodium-caseinate was provided in one of the drinks.

      This resulted in an insulin response not significantly different from that found with the control trial (30 percent greater) and tended to be less than the responses observed after ingestion of the protein hydrolysates.

      After ingestion of the intact protein, blood amino acid responses over this two-hour period were in general lower than the responses observed after ingestion of the protein hydrolysates.

    Conclusions:

      Furthermore, regression analysis of the insulin responses and the changes in the blood amino acid concentrations over the two-hour period showed a strong positive correlation between the observed insulin response and changes in blood leucine, phenylalanine and tyrosine concentrations.

    What Is Leucine?
    An essential amino acid, C4H9CH(NH2)COOH, obtained by the hydrolysis of protein by pancreatic enzymes during digestion and necessary for optimal growth in infants and children and for the maintenance of nitrogen balance in adults.

    What Is Phenylalanine?
    An essential amino acid, C9H11NO2, that occurs as a constituent of many proteins and is normally converted to tyrosine in the human body. It is necessary for growth in infants and for nitrogen equilibrium in adults.

      Interestingly, the addition of free glutamine hardly influenced blood glutamine levels. Also, this study clearly shows that oral ingestion of free arginine is not an effective means of increasing plasma insulin concentrations and blood arginine concentrations.

      The authors concluded that oral intake of protein hydrolysates and amino acids in combination with carbohydrates can result in an insulinotropic effect as much as 100 percent greater than with the intake of carbohydrates only.


Post-Exercise Recovery Drinks:

In another excellent study by Dr. van Loon and co-workers, after an overnight fast, eight male cyclists visited a laboratory on five occasions, during which a control and two different beverage compositions in two different doses were tested.

After they performed a glycogen-depletion exercise, subjects received a beverage (3.5 mL/kg) every 30 minute ensure an intake of 1.2 g/kg/h carbohydrate and zero, 0.2 or 0.4 g/kg/h protein hydrolysate and amino acid mixture.

Insulin Response:

    After the insulin response was expressed as the area under curve, only the ingestion of the beverages containing protein hydrolysate, leucine and phenylalanine resulted in a marked increase in insulin response compared with carbohydrate-only trial.

    Further, a dose-related effect existed because doubling the dose (0.2-0.4 g/kg/h) led to an additional rise in insulin response. Blood leucine, phenylalanine and tyrosine concentrations showed strong correlations with the insulin response.

Blood Amino Acid Concentrations:

    In addition, blood amino acid concentrations were generally lower after the ingestion of drinks containing protein hydrolysate+phenylalanine+leucine compared with the control drinks, although in the latter, considerable amount of protein and amino acids were ingested.

    This suggests that tissue amino acid uptake and post-exercise muscle protein anabolism were increased after the ingestion of protein hydrolysate-amino acid-mixture.

Calbet & Maclean Reports:

    More recently, Drs. Calbet and MacLean at the Copenhagen Muscle Research Center in Denmark reported that the combined administration of glucose and protein hydrolysates stimulates a synergistic release of insulin, regardless of the protein source.

    They concluded that whey protein hydrolysates are absorbed at a faster rate from the small intestine than are whole milk proteins delivered as a milk solution, as reflected by the rapid increase in the blood concentration of branched-chain amino acids in peripheral blood.

    Furthermore, the whey protein hydrolysate elicited the greatest availability of amino acids during the 3-h postprandial period. According to Drs. Calbet and MacLean, the association of high levels of blood amino acids and insulin might explain a superiority of protein hydrolysates over whole proteins in promoting better nitrogen utilization (i.e., greater anabolism), especially when administered in combination with glucose.

Summary:

    In summary, although more research is needed before firm conclusions can be drawn, post-exercise recovery drinks containing protein hydrolysates and insulinotropic amino acids (leucine, phenylalanine) may be of great value for serious gym rats.


Leucine Stimulates Muscle Anabolism Following Resistance Exercise

A recent study by Dr. Koopman and colleagues at the Maastricht University was designed to determine post-exercise muscle protein anabolism following the combined ingestion of carbs with or without protein and/or free leucine.

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Eight Male Subjects Were Randomly Assigned To Three Trials In Which They Consumed Drinks Containing Either:

  1. Carbs alone
  2. Carbs+protein
  3. Carbs+protein+leucine

Following 45 minutes of resistance exercise.

As expected, blood insulin response was higher in the carbs+protein+leucine group compared with the other groups. In addition, muscle protein synthesis rates were higher when protein and free leucine were co-ingested compared with the ingestion of carbs only.

Ingestion of carbs and protein resulted in intermediate muscle protein synthesis rates, so this study clearly shows that the combined ingestion of protein and leucine with carbohydrate stimulates protein anabolism.

The authors concluded,

"The present data indicate that the additional ingestion of free leucine in combination with protein and carbohydrate likely represents an effective strategy to increase muscle anabolism following resistance exercise."


4-Hydroxyisoleucine Boosts Post-Exercise Glycogen Re-Synthesis

4-hydroxyisoleucine, an amino acid that isn't found in mammalian muscle tissue, has unique insulinotropic properties. Because the insulin is a strong potentiator of glycogen synthesis in the muscle, the recent study by Dr. Ruby and colleagues at the University of Montana determined the effects of 4-hydroxyisoleucine with a glucose beverage on rates of post-exercise muscle glycogen re-synthesis in trained male cyclists.

Following an overnight fast, subjects completed a 90-minute glycogen depletion ride after which a muscle biopsy (the removal of muscle tissue) was obtained from the vastus lateralis.


Click To Enlarge.
The Vastus Lateralis.

Immediately & Two Hours After The Muscle Biopsy, Subjects Ingested Either:

  1. glucose (1.8 grams per kilogram body weight)
  2. 4-hydroxyleucine supplement (with the same oral dose of glucose)

With a second muscle biopsy four hours after exercise.

The main finding of this study was that in combination with large simple carb feeding, the added 4-hydroxyleucine promoted a 63 percent higher rate of post-exercise glycogen re-synthesis compared to carbs alone.

Interestingly, there were no significant differences in blood insulin concentration between carbs and carbs+4-hydroxyleucine trials at any time point, so 4-hydroxyleucine appears to enhance glycogen re-synthesis without altering insulin.

References

  1. Stevenson E., Williams C., Biscoe H. (2005) The metabolic responses to high carbohydrate meals with different glycemic indices consumed during recovery from prolonged strenuous exercise. International Journal of Sports Nutrition and Exercise Metabolism, 15(3), June.
  2. Manninen A.H. (2004) Protein hydrolysates in sports and exercise: A brief review. Journal of Sports Science and Medicine 3:60-63. Bucci, L.R., Unlu, L. (2000) Protein and amino acid supplements in exercise and sport. In: Energy-Yielding Macronutrients and Energy Metabolism in Sports Nutrition. Eds. Wolinsky, I., Driskell, J.A. Boca Raton, FL: CRC Press, pp. 191-212.
  3. van Loon, L.J., Saris, W.H.M., Verhagen, H., Wagenmakers, A.J. (2000) Plasma insulin responses after ingestion of different amino acid or protein mixtures with carbohydrate. American Journal of Clinical Nutrition, 72:96-105.
  4. van Loon, L.J., Kruijshoop, M., Verhagen, H., Saris, W.H., Wagenmakers, A.J. (2000) Ingestion of protein hydrolysate and amino acid-carbohydrate mixtures increases postexercise plasma insulin responses in men. Journal of Nutrition, 130:2508-2513.
  5. Calbet, J.A.L., MacLean, D.A. (2002) Plasma glucagons and insulin responses depend on the rate of appearance of amino acids after ingestion of different protein solutions in humans. Journal of Nutrition, 132:2174-2182.
  6. Koopman R., Wagenmakers A.J., Manders R.J., Zorenc A.H., Senden J.M., Gorselink M., Keizer H.A., van Loon L.J. (2005) Combined ingestion of protein and free leucine with carbohydrate increases postexercise muscle protein synthesis in vivo in male subjects. American Journal of Physiology: Endocrinology and Metabolism, 288:E645-E653.
  7. Ruby B.C., Gaskill S.E., Slivka D., Harger S.G. (2005) The addition of fenugreek extract (Trigonella foenum-graecum) to glucose feeding increases muscle glycogen resynthesis after exercise. Amino Acids, 28:71-76.