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Nutritional Strategies In Half Time

Nutritional Strategies In Half Time

 
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Summary
What foods are recommended to obtain a good performance in the second half? The nutritionist’s advice
 

For many years the traditional approach to nutrition between the first and second halves of a match (both in amateur and professional contexts) ) consisted of a glass of tea with sugar and squeezed orange or lemon. Like all strategies that remain over time, it certainly has its merits. Also carbohydrate-rich foods such as tarts, cakes and sweets (even jelly beans) were used in past years for their high available energy content (1). Some authors even suggested the use of Pretzels for their sodium content (1).

On the other hand, these kinds of food contain several ingredients that are not entirely healthy for athletes, such as hydrogenated vegetable fats (trans-fat), artificial colours and additives. These ingredients are not harmful if consumed during a single match, but their negative effects in the long term are still being studied in order to understand how they affect the athletes’ health. Artificial colours and additives often present in these foods have been associated to aggressive behaviour and poor concentration in school age children (2).

Therefore, what is the main factor to be taken into account when planning nutrition in half time?  Several studies have been published discussing physical demands in football and other team sports, and nutritional conditions of participating athletes. Fluids and carbohydrates requirements have been extensively studied in simulated games and training. The investigation of fatigue occurring during matches indicates that fatigue accumulation leads to a gradual decline in performance towards the end of the game. It is still unclear what factors cause fatigue accumulation in football (3,4), also because of the lot of variables to consider, including nutritional factors (hydration and diet before and during the match) together with technical and tactical phenomena and psychological aspects. The type of training practised by the player is also of primary importance (editor’s note).
Few studies exist on specific nutritional strategies in half time and their effects on performance. Authors agree that muscle glycogen levels decrease by 40% up to 90% both in simulated and competitive matches (5-6) (7). Players are often recommended to ingest high carbohydrate amounts in the day of the match, especially in the hours preceding the game, during recovery times and half time (8). The aim is to preserve muscle glycogen, while keeping unchanged blood glucose concentrations [9-10] as much as possible. The physiological response to the ingestion of carbohydrates during exercise is very different from their utilization at rest, like in half time (11).
When isolated carbohydrates are ingested in normal physiological conditions the insulinemic response is aimed at regulating blood glucose.
 
glucosio insulina sangue
 
Conversely, when carbohydrates are ingested during intense exercise an hyperglycaemic reaction is produced by counterregulatory hormones like catecholamines, cortisol and growth hormone (11). It has been demonstrated that the ingestion of a 6% carbohydrate-electrolyte solution (sodium, potassium, chloride etc.) 2 hours before the beginning, 5 min. before each half, every 15 min. during exercise during simulated football matches results in improved shooting precision (12).
When blood glucose decreases below 3.6 mmolL (glycemia 65mg/dL) (25) the availability of brain glucose is compromised, while cognitive functions tend to lower further as the blood concentration decreases to 3.4 mmolL-1 (glycemia 60mg/dL) (13,14). These concentrations can be found also in football players (15,16) during the game. Considering that physical and mental performance seem to  be influenced also by blood glucose levels, the strategies maintaining a stable glycemia may contribute to keep constant optimal performance levels.
The studies based on continuous exercise protocols focus primarily on water absorption. Negative effects observed on gastric emptying and intestinal absorption resulted in a number of recommendations, namely the use of drinks containing 5-8% carbohydrates during activity (17,18,19). As concerns intermittent exercise, limited data are available at present on the effects of carbohydrate supplementation (solutions at 9%). In particular, it was observed that the ingestion of a 20% glucose solution improves sprint performance after 90 minutes of intermittent cycling (20).
The ingestion of a 9,6% carbohydrate-electrolyte solution by non professional players before and during a simulated soccer match play produced higher blood glucose concentrations even beyond 75 min. of play, compared to an electrolyte-rich placebo. Pre-exercise intake of carbohydrates seems to yield similar glycemic responses (17, 21), and the hypoglycaemic rebound seems to decay in the initial phases of exercise, when high glycemic index carbohydrates are consumed (20, 22). It is possible that the use of supplemental carbohydrates during the first half may have ergogenic effects in the last phases of a match, which anyway needs further clear confirmation.
 

It is well known that intense exercise may cause an hyperglicemic response. Physical activity produces a delivery of cathecolamines that inhibits the activity of pancreatic B cells (23). It is plausible that a combination of intense exercise and carbohydrate ingestion during half time may help in maintaining a stable high glycemia in the second half. To support this possibility Achten et al. [17]

Observed that the ingestion of 600 ml of a drink containing maltodestrins during a 25 min warm-up time including sprints and attacking phases resulted in an increased cathecolamine concentration, lower insulinemic response and higher blood glucose levels. Therefore, a re-warm up during half time including high intensity exercise combined with carbohydrate ingestion could be beneficial. Anyway, this type of research protocol is not being considered at present.

Electrolytes in particular can counteract fatigue and muscle cramps in the second half. Sodium is one of the most important electrolytes and it has been demonstrated that sweat sodium losses vary widely, ranging from 1 gr to 6 gr and more in 90 min. Assuming that the players start the match with normal or high sodium levels, the risk of inadequate performance due to sodium depletion is absent. The primary role of supplemental sodium is to favour the utilization of liquids when great quantities of drinks are consumed, like in game pauses. It has been demonstrated that high intensity play phases during competitive matches can originate physical stress such as to delay gastric emptying and even decrease the efficacy of carbohydrate drinks used as supplementation immediately before and during the match (24).
 

It can be easily deduced that the choice must be individualized, because first of all you must take into account the player’s features (tolerance for drinks, solid food, sport-gel, etc.) to favour compliance during half time.

Therefore, foods having following characteristics are recommended:

  • Carbohydrates in concentrations ranging between 8% minimum and 20% maximum
  • Quickly assimilated food. The liquid choice is the simplest and most effective one.
  • Electrolyte containing food. Mineral salts are contained in balanced amounts in sport drinks, but can be low in sport gels and even absent in maltodextrins, etc.

Some examples:

  • Drinks (fruit juices, sport drinks, maltodextrins, etc.)
  • High carbohydrate content sport-gels
  • Tarts

In case powdered electrolytes to be dissolved in water are used, high fixed residue water should be used.

In conclusion, the most important issue is hydration, i.e., to drink liquids in order to replace water resources in the body. Hydration, even with just plain water should begin long before the match and be continued throughout the play and not only during half time.

 

Bibliography

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