soulreaver zei:
If a lighter carbohydrate supplement is desired, however, glycogen synthesis can be enhanced with the addition of protein and certain amino acids. (1)
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 (2)
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 (2)
1. Dietary strategies to promote glycogen synthesis after exercise.
Ivy JL.
Exercise Physiology and Metabolism Laboratory, Department of Kinesiology and Health Education, The University of Texas at Austin, Austin, TX, USA.
2. 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.
Soulraver, dit is wel heel selectief zinnen uit 2 verschillende abstracts posten
Onder mijn opmerkingen staan de gehele abstracts.
Ik heb niet de gehele onderzoeken gelezen, maar wat opmerkingen aan de hand van de abstracts:
- Na krachttraining is het glycogeen in de getrainde spieren laag. Ook is door de training de spier gevoeliger voor insuline geworden, mede doordat de glut-4 receptoren naar de oppervlakte van de cel zijn gekomen. Daardoor zal de meeste glucose na de training naar de getrainde spieren gaan.
- In die 2e abstract gaat het om een glycogeen depletie training. Dit betekent dat er zeer weinig/ geen glycogeen aanwezig meer is. Op dat moment gaat er relatief minder glucose naar de getrainde spieren, omdat het gehele lichaam glucose nodig heeft.
Zo speelt de lever bijvoorbeeld ook een zeer grote rol en is de hoeveelheid glycogeen in de lever een belangrijke indicatie(fed of fasted state). Wanneer je lever geen glycogeen bevat dan verkeer je ook niet in een anabole staat.
- In de samenvattingen staat duidelijk dat een snelle aanvoer van glucose de beste resultaten levert.
- Glucose heeft meer functies dan het glycogeen zo snel mogelijk aanvoeren. Zo zijn de cortisol waardes na een training hoger. Een hogere insuline piek zorgt ervoor dat deze cortisol verhoging snel afneemt.
Ook zorgt insuline ervoor dat de eiwit afbraak gestopt wordt.
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De gehele samenvattingen:
1.) Dietary strategies to promote glycogen synthesis after exercise.
Ivy JL.
Exercise Physiology and Metabolism Laboratory, Department of Kinesiology and Health Education, The University of Texas at Austin, Austin, TX, USA.
Muscle glycogen is an essential fuel for prolonged intense exercise, and therefore it is important that the glycogen stores be copious for competition and strenuous training regimens. While early research focused on means of increasing the muscle glycogen stores in preparation for competition and its day-to-day replenishment, recent research has focused on the most effective means of promoting its replenishment during the early hours of recovery.
It has been observed that muscle glycogen synthesis is twice as rapid if carbohydrate is consumed immediately after exercise as opposed to waiting several hours, and that a rapid rate of synthesis can be maintained if carbohydrate is consumed on a regular basis. For example, supplementing at 30-min intervals at a rate of 1.2 to 1.5 g CHO x kg(-1) body wt x h(-1) appears to maximize synthesis for a period of 4- to 5-h post exercise. If a lighter carbohydrate supplement is desired, however, glycogen synthesis can be enhanced with the addition of protein and certain amino acids. Furthermore, the combination of carbohydrate and protein has the added benefit of stimulating amino acid transport, protein synthesis and muscle tissue repair. Research suggests that aerobic performance following recovery is related to the degree of muscle glycogen replenishment.
2) 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 (> or =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.