How glycogen is stored

When we talk about how glycogen is stored, we're talking about the timing of carbohydrate intake, which is essential for restoring our energy stores.

To understand the importance of timing CHO intake, it is necessary to understand the two phases of its resynthesis. Thus, different studies have indicated that glycogen resynthesis after exercise occurs following a biphasic pattern (1) . Initially, there is a rapid increase in the resynthesis rate, independent of insulin concentrations and lasting approximately 30-60 minutes after exercise; this supports the high glycogen synthesis in the 60 minutes immediately following the end of exercise (2) . Therefore, at Fanté we recommend innovative modes of use with respect to current recovery programs , differentiating time and dose according to the athlete's weight, something never seen in any mode of use to date.

In this phase, an increase in the translocation of the glucose transporter protein (GLUT-4) can be observed, due to an increase in calcium concentrations at the level of the rhabdomyocyte sarcoplasm (a consequence, in turn, of the multiple action potentials that take place during the effort) (3) , up to two times, gradually decreasing until reaching pre-exercise levels 2 hours after its completion (4)

As for liver glycogen, it is rapidly restored during post-exercise food intake with a content of 0.2 to 0.5 grams fructose/kg weight, helping to maintain normoglycemia or, when CHO intake is not performed post-exercise, via gluconeogenic means from lactate (5) . In light of the above, there appears to be a potential post-exercise window of opportunity that athletes should take advantage of for the recovery of muscle glycogen (6) .

In fact, when immediate CHO ingestion is compared to an ingestion up to 2 hours post-exercise, it results in 45% lower muscle glycogen concentrations (7). Therefore, those whose sports are highly glycogen-dependent, e.g., triathlon, running, trail running, swimming, cycling, soccer, among others, should be encouraged to replenish glycogen as soon as possible after completing the event (6) .

In the context of recovery from exhaustive exercise, it is known that an intake of 6-12 g/kg is sufficient to restore endogenous glycogen stores when the recovery time is ≥ 24h ( 8 , 9) .

However, when recovery time is limited (<8h), specific strategies aimed at accelerating glycogen resynthesis become necessary (2) . Similar to the effects of the glycemic index of foods over longer periods (i.e., 24h), the frequency of CHO intake does not seem to influence muscle glycogen resynthesis, however, when recovery time is limited, the frequency at which CHO is ingested may have an influence. This has been demonstrated in studies showing that when CHO is ingested at intervals of 15-30 minutes, the rate of muscle glycogen resynthesis is approximately 40% higher than when it is supplied every two hours (10, 11 , 12).

However, although there are currently no studies that directly examine the frequency of CHO administration on the rate of muscle glycogen storage, it seems reasonable, based on the studies discussed above, that when rapid glycogen repletion is needed during short-term recovery, a frequent intake feeding pattern should be used (2) . As discussed and explained in the 3:1 recovery guide .

Amount of carbohydrate intake

Regarding the recommended amount of CHO for glycogen replenishment, van Loon et al. (12) showed how the intake of 1.2 g/kg/hour of CHO resulted in a 150% higher glycogen resynthesis (from 17 to 45 mmol/kg dm/h) in relation to a lower dose of 0.8 g/kg/hour (12) . Searching for the optimal amount in this regard, Howarth et al. (2009), (13) showed how the ingestion of 1.6 g/kg/hour did not stimulate glycogen resynthesis more, considering that the recommended amount of post-exercise CHO will be around 1.0-1.5 g/kg/hour maximum within the first hour after cessation of exercise and will continue with an intake of 1.0-1.5 g/kg/h every 4-6 hours or until resuming regular meals (14).

Type of carbohydrates

An important factor determining muscle glycogen resynthesis is insulin-mediated glucose uptake into muscle cells. Ingestion of moderate to high glycemic index (GI) CHO is a good option to achieve glycogen restoration, in part, by providing rapid glucose availability and insulin response (15), as it has been shown to increase muscle glycogen resynthesis in the 6 hours post-exercise compared to low glycemic index CHO sources.

When fructose is compared with glucose or sucrose, it is observed that the insulinemic response is lower in the former, which is attributed to a greater use of this monosaccharide in the resynthesis of hepatic glycogen (2 , 16) .

On the other hand, glucose and sucrose seem to have a similar effect on muscle glycogen resynthesis as was recently demonstrated in a study, where it was shown that the intake of 1.2 g/kg/h of glucose, glucose + fructose or glucose + sucrose during recovery caused similar rates of muscle glycogen resynthesis (17) . In relation to this, it is recommended to ingest a mixture of glucose + fructose in a 2:1 ratio that provides an optimal dose of CHO for the effective restoration of liver and muscle glycogen, which reduces gastrointestinal discomfort caused by the high intake of CHO of a single type as most recoverys on the market. (2)

The ingestion of liquid or solid forms of CHO appear to be equally effective in restoring muscle glycogen, so the individual preference of the athlete should prevail (18) . However, and as Ranchordas (2017) (6) points out, from a practical perspective it would be interesting, given the high prevalence of gastrointestinal problems due to the consumption of high amounts of CHO, that athletes have access to mixtures of both solid and liquid foods, in order to avoid these problems. In addition, the athlete's preferences (taste), practicality (two sessions a day, for example), availability (post-competition travel, stadium / sporting events, for example) and something important, that they promote the desire to eat in athletes, so that the required needs can be acquired, since there may be a marked decrease in appetite after sporting events. Therefore, the use of liquid carbohydrate drinks is advisable in these situations.

Protein YES or NO in recovery

Various nutritional factors are being studied to enhance glycogen resynthesis in conjunction with CHO intake (Figure 1). Several studies have shown that the simultaneous intake of CHO and protein may be beneficial for glycogen resynthesis (13) . This is because protein intake increases insulin secretion by the pancreas, stimulating glycogen resynthesis.

The type of protein seems to influence insulin secretion. Hydrolyzed protein (isolate) has been shown to have a greater effect on insulin secretion than intact protein, which is related to its faster digestion and absorption rate (19 , 20) . Furthermore, whey protein appears to be a greater insulin stimulator than casein, possibly due to its higher leucine content (21) . Therefore, we use whey protein isolate rather than other types in our GLYCOGEN RECOVERY DRINK.

The addition of at least 0.3-0.4 g/kg/h of protein may be required to achieve this synergistic effect of CHO and protein mixture on insulin release (2).

So carbs and protein 3:1?

Glutamine

Glutamine is a conditionally essential amino acid widely used in sports nutrition, especially for its immunomodulatory role. However, glutamine performs several other biological functions, such as cell proliferation, energy production, glycogenesis, ammonia buffering, and maintaining acid-base balance, among others.

Another potential anti-fatigue property of glutamine is its ability to prevent dehydration. Glutamine is transported across the intestinal brush border by a sodium-dependent system, which promotes faster absorption of fluids and electrolytes in the intestine. Therefore, including glutamine in rehydration solutions could increase sodium absorption and water flow.

The amount of sodium

When we eat a recovery diet, it must have a good supply of carbohydrates appropriate for our weight, the 2:1 carbohydrate type, protein in an adequate amount, and an adequate amount of specific minerals with the goal of replenishing what we have expended.

The quantity is essential not only to replenish salts, but also because the high amount and hypertonic nature of the drink promotes the entry of solute (cho) into the cell more quickly than an isotonic (single-dose) or hypotonic drink. Therefore, at FANTÉ, we opted for a hypertonic recovery drink based on current scientific evidence, adding 0.8g of sodium per dose for those weighing up to 50kg and 1.5g of sodium for those weighing more than 90kg per dose. Check out our instructions on the back of the recovery drink or our instructions on the website.

REMEMBER that being hypotonic you resynthesize glycogen very quickly but you are not hydrated, so we advise you to prepare another bottle of water and drink from that as well and not just Fanté GLYCOGEN exclusively.

Creatine

Creatine has also been studied for its synergistic action on glycogen resynthesis. Studies have shown how creatine monohydrate ingestion increases the expression of genes involved in different activities, including glycogen resynthesis, which is suggested to be mediated by the osmotic effect of this ergogenic aid ( 22) . Robert et al. (2016) (23) observed an increase in post-exercise glycogen storage following creatine supplementation (20 g/day) with a high-CHO diet. This was most evident 24 h after exercise and was maintained for 6 days of post-exercise recovery with a high-CHO diet. It is important to consider the 1-2% body weight gains that may be due to creatine use, which may interfere with some sports where weight gain can impair performance (e.g., high jump) (14).

When we formulated our recovery program, we considered including creatine as a synergistic agent with glutamine, protein, carbohydrates, and minerals for optimal recovery. However, the inability to use the recovery program during periods of non-creatine use, such as periodizing supplementation during specific times of the season, led us to change our minds and opt out of including it.

Since if the athlete does not want to include creatine for X reasons (periodization, symptoms, etc.), by including it in our Recovery we would mean that the athlete could not consume the recovery at those times.

Caffeine

Another nutrient studied in this regard is caffeine. Thus, a study observed that the ingestion of 8 mg/kg of caffeine together with CHO (1 g/kg/h) resulted in a substantial increase in glycogen content during 4 hours of post-exercise recovery (24) .

However, the possible interference of such high amounts of caffeine in the athlete's sleep should be taken into account. In addition, other similar studies have found no difference in glycogen content (25) . A recent systematic review has analyzed how different compounds contained in coffee can affect muscle glycogen resynthesis, showing how some of these compounds can activate different molecular pathways leading to an increase in muscle glycogen synthesis, which leads the authors to conclude that coffee may be an option in the recovery of athletes. Further studies are still needed.

Alcohol

Finally, it should be noted that alcohol can interfere with glycogen repletion. In this regard, Burke et al. (2003) (26) showed how alcohol ingestion (approximately 120 g) could indirectly interfere with glycogen storage during recovery by displacing CHO ingestion. However, the direct effects remain to be elucidated.

Literature

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2. Alghannam, A., Gonzalez, J., & Betts, J. (2018). Restoration of Muscle Glycogen and Functional Capacity: Role of Post-Exercise Carbohydrate and Protein Co-Ingestion. Nutrients, 10(2), 253. https://doi org/10.3390/nu10020253
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26. Burke, LM, Collier, GR, Broad, EM, Davis, PG, Martin, DT, Sanigorski, AJ, & Hargreaves, M. (2003). Effect of alcohol intake on muscle glycogen storage after prolonged exercise. Journal of Applied Physiology (Bethesda, Md. : 1985), 95(3), 983–990. https://doi. org/10.1152/japplphysiol.00115.2003