Comparison of carbohydrate and milk-based beverages on muscle damage and glycogen following exercise.
Wojcik JR, Walber-Rankin J, Smith LL, Gwazdauskas FC.
Department of Human Nutrition, Foods, and Exercise at Virginia Polytechnic Institute and State University, Blacksburg 24061, USA.
This study examined effects of carbohydrate (CHO), milk-based carbohydrate-protein (CHO-PRO), or placebo (P) beverages on glycogen resynthesis, muscle damage, inflammation, and muscle function following eccentric resistance exercise. Untrained males performed a cycling exercise to reduce muscle glycogen 12 hours prior to performance of 100 eccentric quadriceps contractions at 120% of 1-RM (day 1) and drank CHO (n = 8), CHO-PRO (n = 9; 5 kcal/kg), or P (n = 9) immediately and 2 hours post-exercise. At 3 hours post-eccentric exercise, serum insulin was four times higher for CHO-PRO and CHO than P (p < .05). Serum creatine kinase (CK) increased for all groups in the 6 hours post-eccentric exercise (p < .01), with the increase tending to be lowest for CHO-PRO (p < .08) during this period. Glycogen was low post-exercise (33+/-3.7 mmol/kg ww), increased 225% at 24 hours, and tripled by 72 hours, with no group differences. The eccentric exercise increased muscle protein breakdown as indicated by urinary 3-methylhistidine and increased IL-6 with no effect of beverage. Quadriceps isokinetic peak torque was depressed similarly for all groups by 24% 24 hours post-exercise and remained 21% lower at 72 hours (p < .01). In summary, there were no influences of any post-exercise beverage on muscle glycogen replacement, inflammation, or muscle function.
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Type and timing of protein feeding to optimize anabolism.
Mosoni L, Mirand PP.
PURPOSE OF REVIEW
The delivery rate of amino acids to an organism significantly affects protein anabolism. The rate can be controlled by the type and the timing of feeding. Our aim was to bring new insights to the way they may act.
RECENT FINDINGS
During young and adult ages, when food supply is liberal, subjects can adapt to various modes of protein feeding. However, during food restriction, protein anabolism is favored when the delivery of amino acids is evenly distributed over the day, either with frequent meals, or through the use of slowly absorbed proteins like casein. In contrast, during aging, quickly absorbed protein sources become more efficient. During recovery after exercise, the timing of protein feeding after the end of exercise may or may not influence its anabolic effect, depending on the subject's age and the type of exercise.
SUMMARY
The synchronization of variations in anabolic capability with amino acid supply partly explains the effects of the type and timing of protein feeding. This effect is modulated by the amount of amino acids required to increase whole-body proteins and by the signaling properties of some amino acids to stimulate protein synthesis. Indeed, the anabolic effect of amino acids is determined by their interaction with other anabolic factors (other nutrients or physiological factors, whose efficiency is mainly related to their effect on protein degradation). It is clear that benefits can be obtained from adapted protein feeding patterns.
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Simple and complex carbohydrate-rich diets and muscle glycogen content of marathon runners.
Roberts KM, Noble EG, Hayden DB, Taylor AW.
Faculty of Physical Education, University of Western Ontario, London, Canada.
The effects of simple-carbohydrate (CHO)- and complex-CHO-rich diets on skeletal muscle glycogen content were compared. Twenty male marathon runners were divided into four equal groups with reference to dietary consumption: depletion/simple, depletion/complex, nondepletion/simple, and nondepletion/complex. Subjects consumed either a low-CHO (15% energy [E] intake), or a mixed diet (50% CHO) for 3 days, immediately followed by a high-CHO diet (70% E intake) predominant in either simple-CHO or in complex-CHO (85% of total CHO intake) for another 3 days. Skeletal muscle biopsies and venous blood samples were obtained one day prior to the start of the low-CHO diet or mixed diet (PRE), and then again one day after the completion of the high-CHO diet (POST). The samples were analysed for skeletal muscle glycogen, serum free fatty acids (FFA), insulin, and lactate and blood glucose. Skeletal muscle glycogen content increased significantly (p less than 0.05) only in the nondepletion/simple group. When groups were combined, according to the type of CHO ingested and/or utilization of a depletion diet, significant increases were observed in glycogen content. Serum FFA decreased significantly (p less than 0.05) for the nondepletion/complex group only, while serum insulin, blood glucose, and serum lactate were not altered. It is concluded that significant increases in skeletal muscle glycogen content can be achieved with a diet high in simple-CHO or complex-CHO, with or without initial consumption of a low-CHO diet.
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Amino acids regulate skeletal muscle PHAS-I and p70 S6-kinase phosphorylation independently of insulin. Long, W., L. Saffer, L. Wei, and E. J. Barrett. Department of Internal Medicine, University of Virginia Health Sciences Center, Charlottesville, Virginia 22908
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APStracts 7:0077E, 2000.
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Refeeding reverses the muscle protein loss seen with fasting. The physiological regulators and cellular control sites responsible for this reversal are incompletely defined. Phosphorylation of phosphorylated heat-acid stabled protein (PHAS-I) frees eukaryotic initiation factor 4E (eIF4E) and stimulates protein synthesis by accelerating translation initiation. Phosphorylation of p70 S6-kinase (p70S6k) is thought to be involved in the regulation of the synthesis of some ribosomsal proteins and other selected proteins with polypyrimidine clusters near the transcription start site. We examined whether phosphorylation of PHAS-I and p70S6k was increased by feeding and determined the separate effects of insulin and amino acids on PHAS-I and p70S6k phosphorylation in rat skeletal muscle in vivo. Muscle was obtained from rats fed ad libitum or fasted overnight (n = 5 each). Other fasted rats were infused with insulin (3 muU×min«minus»1×kg«minus»1, euglycemic clamp), amino acids, or the two combined. Gastrocnemius was freeze-clamped, and PHAS-I and p70S6k phosphorylation was measured by quantifying the several phosphorylated forms of these proteins seen on Western blots. We observed that feeding increased phosphorylation of both PHAS-I and p70S6k (P < 0.05). Infusion of amino acids alone reproduced the effect of feeding. Physiological hyperinsulinemia increased p70S6K (P < 0.05) but not PHAS-I phosphorylation (P = 0.98). Addition of insulin to amino acid infusion was no more effective than amino acids alone in promoting PHAS-I and p70S6k phosphorylation. We conclude that amino acid infusion alone enhances the activation of the protein synthetic pathways in vivo in rat skeletal muscle. This effect is not dependent on increases in plasma insulin and simulates the activation of protein synthesis that accompanies normal feeding.
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The use of High GI would be extremely helpful in endurance type training since the object is to fill glycogen stores (both muscle and liver) to account for the energy expenditure that will follow. With resistance training there is no further energy expenditure that will deplete glyocgen stores further so the need for such drastic spikes and quick replenishment is not needed. People also say that you must refill stores quickly to eliminate catabolism. Well GH is produced at high levels well after (50-60minutes) after exercise is completed so the whole catabolism is overrated. It's important but overrated.
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People keep thinking I'm anti-insulin but that would be nuts. I just prefer a more stable release that will coincided with both phases (if it even needed in phase 1) There has been no evidence that a high SPIKE in insulin increases the rate of synthesis. It just increases the glycogen storage quicker.
Amino acids stimulate translation initiation and protein synthesis through an Akt-independent pathway in human skeletal muscle.
Liu Z, Jahn LA, Wei L, Long W, Barrett EJ.
Division of Endocrinology and Metabolism, Department of Internal Medicine, University of Virginia Health Sciences Center, Charlottesville, Virginia 22908, USA.
zl3e@virginia.edu
Studies in vitro as well as in vivo in rodents have suggested that amino acids (AA) not only serve as substrates for protein synthesis, but also as nutrient signals to enhance mRNA translation and protein synthesis in skeletal muscle. However, the physiological relevance of these findings to normal humans is uncertain. To examine whether AA regulate the protein synthetic apparatus in human skeletal muscle, we infused an AA mixture (10% Travesol) systemically into 10 young healthy male volunteers for 6 h. Forearm muscle protein synthesis and degradation (phenylalanine tracer method) and the phosphorylation of protein kinase B (or Akt), eukaryotic initiation factor 4E-binding protein 1, and ribosomal protein S6 kinase (p70(S6K)) in vastus lateralis muscle were measured before and after AA infusion. We also examined whether AA affect urinary nitrogen excretion and whole body protein turnover. Postabsorptively all subjects had negative forearm phenylalanine balances. AA infusion significantly improved the net phenylalanine balance at both 3 h (P < 0.002) and 6 h (P < 0.02). This improvement in phenylalanine balance was solely from increased protein synthesis (P = 0.02 at 3 h and P < 0.003 at 6 h), as protein degradation was not changed. AA also significantly decreased whole body phenylalanine flux (P < 0.004). AA did not activate Akt phosphorylation at Ser(473), but significantly increased the phosphorylation of both eukaryotic initiation factor 4E-binding protein 1 (P < 0.04) and p70(S6K) (P < 0.001). We conclude that AA act directly as nutrient signals to stimulate protein synthesis through Akt-independent activation of the protein synthetic apparatus in human skeletal muscle.
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Determinants of post-exercise glycogen synthesis during short-term recovery.
Jentjens R, Jeukendrup A.
Human Performance Laboratory, School of Sport and Exercise Sciences, University of Birmingham, Edgbaston, Birmingham, UK.
The pattern of muscle glycogen synthesis following glycogen-depleting exercise occurs in two phases. Initially, there is a period of rapid synthesis of muscle glycogen that does not require the presence of insulin and lasts about 30-60 minutes. This rapid phase of muscle glycogen synthesis is characterised by an exercise-induced translocation of glucose transporter carrier protein-4 to the cell surface, leading to an increased permeability of the muscle membrane to glucose. Following this rapid phase of glycogen synthesis, muscle glycogen synthesis occurs at a much slower rate and this phase can last for several hours. Both muscle contraction and insulin have been shown to increase the activity of glycogen synthase, the rate-limiting enzyme in glycogen synthesis. Furthermore, it has been shown that muscle glycogen concentration is a potent regulator of glycogen synthase. Low muscle glycogen concentrations following exercise are associated with an increased rate of glucose transport and an increased capacity to convert glucose into glycogen.The highest muscle glycogen synthesis rates have been reported when large amounts of carbohydrate (1.0-1.85 g/kg/h) are consumed immediately post-exercise and at 15-60 minute intervals thereafter, for up to 5 hours post-exercise. When carbohydrate ingestion is delayed by several hours, this may lead to ~50% lower rates of muscle glycogen synthesis. The addition of certain amino acids and/or proteins to a carbohydrate supplement can increase muscle glycogen synthesis rates, most probably because of an enhanced insulin response. However, when carbohydrate intake is high (>/=1.2 g/kg/h) and provided at regular intervals, a further increase in insulin concentrations by additional supplementation of protein and/or amino acids does not further increase the rate of muscle glycogen synthesis. Thus, when carbohydrate intake is insufficient (<1.2 g/kg/h), the addition of certain amino acids and/or proteins may be beneficial for muscle glycogen synthesis. Furthermore, ingestion of insulinotropic protein and/or amino acid mixtures might stimulate post-exercise net muscle protein anabolism. Suggestions have been made that carbohydrate availability is the main limiting factor for glycogen synthesis. A large part of the ingested glucose that enters the bloodstream appears to be extracted by tissues other than the exercise muscle (i.e. liver, other muscle groups or fat tissue) and may therefore limit the amount of glucose available to maximise muscle glycogen synthesis rates. Furthermore, intestinal glucose absorption may also be a rate-limiting factor for muscle glycogen synthesis when large quantities (>1 g/min) of glucose are ingested following exercise.
So what does that mean?
You do NOT need an insulin spike to get the ball rolling, there IS a chance of fat deposition and the rate of absorbtion of High GI carbs may well be limited by the intentine such that a low GI would (and does) work equally as well for MOST people.
Also, the guys that are taking huge amounts of high GI hoping to induce a large insulin spike are just kidding themselves as the intestinal glucose absorption rates will ensure most of it is going to waste.
The arguement has been made that oats are useless PWO due to their slow digestion rate, but if the intestinal absorbtion rate limits the absorbtion of the PWO carbs anyway, then the slow digestion rate may not be as big an issue as they make out.
Carbohydrate nutrition before, during, and after exercise.
Costill DL.
The role of dietary carbohydrates (CHO) in the resynthesis of muscle and liver glycogen after prolonged, exhaustive exercise has been clearly demonstrated. The mechanisms responsible for optimal glycogen storage are linked to the activation of glycogen synthetase by depletion of glycogen and the subsequent intake of CHO. Although diets rich in CHO may increase the muscle glycogen stores and enhance endurance exercise performance when consumed in the days before the activity, they also increase the rate of CHO oxidation and the use of muscle glycogen. When consumed in the last hour before exercise, the insulin stimulated-uptake of glucose from blood often results in hypoglycemia, greater dependence on muscle glycogen, and an earlier onset of exhaustion than when no CHO is fed. Ingesting CHO during exercise appears to be of minimal value to performance except in events lasting 2 h or longer. The form of CHO (i.e., glucose, fructose, sucrose) ingested may produce different blood glucose and insulin responses, but the rate of muscle glycogen resynthesis is about the same regardless of the structure.
PMID: 3967778 [PubMed - indexed for MEDLINE]
So a high GI may well ilicite a different blood glucose and insulin response, but in the end it doesnt make any difference.
I use LOW GI for one very simple reason.
Im looking to drop bf while adding muscle, and it is working for me.
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