0
0,00  0 artículos

No hay productos en el pedido

Iñigo Mujika

Fisiología y entrenamiento

Nutrition in team sports

Iñigo
Mujika
22 de abril de 2010

Girl drinking water

The fifth Sports Nutrition Conference was organised in Cala Serena, Mallorca (Spain) last December 2-3, 2009. In this beautiful setting we had an impressive line up of speakers, including Prof. Asker Jeukendrup, Prof. Tim Noakes, Dr. David Stensel, Prof. Mark Tarnopolsky and Dr. Kevin Tipton. At this conference, I presented on Team Sport Nutrition. Here is a summary of my presentation.

Introduction

Sound hydration and nutritional strategies have been shown to be performance-determining factors in prolonged, continuous moderate-to-high intensity exercise. Although the impact of these strategies on performance during intermittent, high-intensity exercise that characterizes team sports has not been studied as extensively, there is enough scientific evidence available to suggest that team sport-specific hydration and nutrition strategies can have a major impact on performance.

The purpose of this article is to provide a series of guidelines on hydration and nutrition for enhancing the performance of team sport players, based on the specific physiological characteristics and energetic demands of team sports, and considering the nutritional factors that could contribute to fatigue in team sports.

Physiological characteristics of team sports

Most team sports (e.g. basketball, football, hockey, rugby, volleyball) can be described as moderate-to-long duration exercise including repeated bouts of high intensity activity interspersed with periods of low-to-moderate active recovery or passive rest. From a physiological perspective, team sports are characterized by the moderate-to-long distances covered by the players during match play (e.g. 8 to 12 km in association football), but also the variable activity pattern (e.g. in excess of 800 activity changes per football match, including walking, jogging, cruising, sprinting, backing, jumping, tackling and heading [Hawley & Burke 1998]). Players’ ability to perform repeated sprints with short duration recovery in between is an important determinant of performance in intermittent team sports.

This activity pattern determines to a great extent the physiological requirements of team sports. As shown by physiological measurements conducted during match play, these requirements include not only a high aerobic capacity, but also a high glycolytic capacity and a well-developed phosphocreatine breakdown/resynthesis system (Bangsbo 1994).

Nutritional factors that could produce fatigue in team sports

Various nutritional factors could be associated with fatigue in team sports. Muscle glycogen depletion causes a reduction in the distance covered by football players during the second half of a match. Krustrup et al. (2006) observed that muscle glycogen was reduced by 42% after a football game. Before the game, 73% of all muscle fibers were rated as full with glycogen, whereas only 19% were still full at the end of it. Moreover, 36% of all individual fibers were almost empty of glycogen after the game, another 11% were completely empty, and 54%, 46% and 25%of ST, FTa and FTx fibers, respectively, were completely or almost empty of glycogen.

These authors suggested that fatigue and reduced ability to perform single or repeated sprints towards the end of a football game may be associated with reduced glycogen levels in individual muscle fibers (Krustrup et al. 2006). Dehydration, which has been show to occur during team sport competition (Burke and Hawley 1997), is also directly related to reduced exercise capacity, increased perception of effort, and deterioration of mental performance and football skill performance (Table 1).

Table 1. Fluid balance measurements in selected team sports (adapted from Burke and Hawley 1997).
Sport Temperature (º C) Humidity (%) Sweat loss (ml) Fluid intake (ml) Hypohydration (% MB)
Rugby 18-20 18-20 2160 751 1.6
Rugby 24-25 30-32 2100 150 2.5
Football 33 40 2089 657 2.5
Football 26 78 2546 242 2.9
Football 13 7 1570 0 2.1

Sweat rate and sweat composition vary extensively between individuals, and quantification of these losses plays a role in the individualisation of a hydration strategy to optimise training and competitive performance. Various studies have shown that elite football players do not drink sufficient volume to replace their sweat loss during training and competition. Maughan et al. (2007) measured fluid balance and sweat electrolyte losses during a competitive football match played at an ambient temperature of 6-8 degrees C (relative humidity 50-60%).

Study results showed a large individual variability in hydration status, sweat losses, and drinking behaviours in this cool environment, highlighting the need for individualized assessment of hydration status to optimize fluid-replacement strategies. The net fluid loss during a football game in the heat often reaches >2% of body mass, and correlations can be observed between net-fluid loss and repeated sprint test fatigue index after the game.

McGregor et al. (1999) examined the effect of intermittent high-intensity shuttle running and fluid ingestion on the performance of a football skill in semi-professional players. Performance of the skill test after a trial with no fluid deteriorated by 5%, but was maintained during the fluid ingestion trial. In addition, mean heart rate, perceived exertion, serum aldosterone, osmolality, sodium and cortisol responses during the test were higher when no fluid was ingested. Nevertheless, Edwards and Noakes (2009) suggest that dehydration is only an outcome of complex physiological control (operating a pacing plan) and no single metabolic factor is causal of fatigue in elite soccer. Other hydration and nutritional factors that could produce fatigue in football include hypoglycemia, other mechanisms of “central fatigue” involving neurotransmitters, hyponatremia, and gastrointestinal discomfort and upset.

Diet and team sport performance

Dietary CHO intake affects team sport performance. Balsom and colleagues (1999) compared movement and technical parameters of performance and selected physiological responses in football players twice, following an exercise and diet (either high- approximately 65% or low- approximately 30% CHO intake) regimen designed to manipulate muscle glycogen concentrations. Pre-game muscle glycogen concentrations following the high CHO diet were significantly higher than following the low-CHO diet, and the players performed 33% more high intensity exercise in the game played following the high-CHO diet.

These authors suggested that to optimise multiple sprint performance a high-CHO diet should be administered in preparation for intense training and competition (Balsom et al. 1999). Abt et al. (1998) examined the effect of a high-CHO diet on the performance of dribbling and shooting skills of football players. They indicated that the high-CHO diet did not increase the ability of players to shoot or dribble, and speculated that either muscle glycogen depletion may not impair the ability of the player to execute game skills; alternative fatigue mechanisms such as dehydration or increased lactate production may be causative factors in the reduction in skill performance; or the treadmill protocol employed failed to induce a degree of glycogen depletion or fatigue large enough to cause a significant fall in skill performance (Abt et al. 1998).

Team sport athlete´s dietary habits

Dietary habits of team sport athletes’ have not been as well studied as those of individual sport athletes. Clark and colleagues (2003) reported on baseline dietary data and performance indices of female football players during rigorous twice a day pre-season training and then during the post-competitive season. Total energy, CHO, protein, and fat intakes were significantly greater during the pre-season. Pre-season energy intake met the daily recommended intakes for females with an “active” lifestyle (37 kcal/kg). Carbohydrate intake failed to meet recommendations to promote glycogen repletion (7-10 g/kg), whereas protein and fat intakes were above minimum recommendations. Pre- and post-season intakes of vitamin E, folate, copper, and magnesium were below 75% of those recommended.

In a similar investigation, Iglesias-Gutiérrez et al. (2005) assessed the food habits and nutritional status of high level adolescent football players living in their home environment. Daily energy expenditure and energy intake were 12.5 MJ and 12.6 MJ, respectively. Protein (16% of energy intake; 1.9 g/kg of body mass), lipid (38%), and cholesterol (385 mg) intake were above recommendations, while CHO (45%) was below. The food intake of these adolescents was based on cereals and derivates; meat, fish, and eggs; milk and dairy products; biscuits and confectionery; and oil, butter and margarine, which provided 78% of total energy intake, 85% of proteins, 64% of carbohydrates, 90% of lipids, and 47% of fiber. Although diet provided sufficient iron, 48% of individuals showed iron deficiency without anemia. In general, the contribution of CHO to total energy intake is lower than that recommended for athletes.

Garrido et al. (2007) reported on the adequacy of either a “buffet-style” diet and a fixed “menu-style” diet in a group of elite adolescent football players. The set “menu” provided significantly higher total energy and CHO intakes than the “buffet”, but calories from fat were excessive in both settings. Calcium and vitamin D were below recommendations in the “buffet”, and fiber, magnesium, folate, vitamin A, and vitamin E intake fell below recommended values in both settings. All of the above suggest that well designed nutritional education and interventions are necessary to optimize performance and promote healthy eating habits in team sport players.

Fluid and energy intake during team sport activity

Given the intermittent nature of team sports, they often offer frequent opportunities to ingest fluid and energy during breaks between periods, time-outs, substitutions or breaks in play (Burke and Hawley 1997). Drinking opportunities for selected team sports are summarised in Table 2.

Table 2. Opportunities to drink during match-play in selected team sports (adapted from Burke and Hawley 1997).
Sport Intervals of play Opportunities to drink Comments
Basketball 4 x 10-12 min. + substantial time-on, unlimited substitutions, time-outs. Quarter-time breaks, time-outs, substitutions. Fluids must be consumed on court sidelines.
Field hockey 2 x 35 min., unlimited substitutions. Half-time, substitutions, pauses in play. Fluids must be consumed at sidelines; players must not leave field.
Ice hockey 3 x 20 min. + susbtantial time-on, unlimited substitutions, time-outs. Third-time breaks, time-outs, substitutions, pauses in play. Players must drink at bench.
Rugby 2 x 40 min., limited substitutions. Half-time break, substitutions, pauses in play. Trainers may run onto field with fluid bottles during pauses in play.
Football 2 x 45 min., substitutions whithout replacement. Half-time brek, pauses in play (drink must be taken at sideline). Fluids must be consumed at sidelines; players must not leave field.
Volleyball First to 3 sets, limited substitutions, time-outs. Time-outs, substitutions, breaks between sets. Fluids must be consumed at sidelines.

Nicholas et al. (1995) examined the effects of ingesting a 6.9% CHO-electrolyte (CHO-E) solution on endurance capacity during a prolonged intermittent, high-intensity shuttle running test. The solution was ingested immediately prior to exercise (5 ml/kg) and every 15 min thereafter (2 ml/kg). The subjects were able to continue running longer when fed the CHO-E solution. In addition, a CHO-E solution enables subjects with compromised glycogen stores to better maintain skill and sprint performance during intermittent shuttle running, football passing and shooting than when ingesting fluid alone. In addition to the physiological and metabolic benefits, investigations on the effects of CHO ingestion during prolonged high-intensity intermittent exercise on affect and perceived exertion indicate that perceived activation is lower without CHO ingestion during the last 30 min of exercise, and this is accompanied by lowered plasma glucose concentrations. When CHO is ingested, RPE is maintained in the last 30 min of exercise. Thus, CHO ingestion during prolonged high-intensity exercise elicits an enhanced perceived activation profile that may impact upon task persistence and performance.

Clarke et al. (2005) investigated the effect of the provision of sports drink during football-specific exercise. On two occasions, 7 mL/kg CHO-E or placebo (PLA) solutions were ingested at 0 and 45 min. On a third trial, the same volume of CHO-E was consumed in smaller volumes at 0, 15, 30, 45, 60, and 75 min. This manipulation of the timing and volume of ingestion elicited similar metabolic responses without affecting exercise performance. However, consuming fluid in small volumes reduced the sensation of gut fullness. A recent investigation on the effects of low- and high-glycemic index (GI) foods on metabolism and performance during 90 min of high-intensity intermittent exercise indicated that, compared with fasting, both low-GI and high-GI foods consumed 3 h before (1.3 g/kg CHO) and halfway (0.2 g/kg CHO) through exercise improved repeated sprint performance. High-GI foods impaired fat oxidation during exercise, without influencing performance (Little et al. 2009). Nevertheless, limitations exist regarding the ability of team sport athletes to ingest fluid during match-play. Indeed, gastric emptying of liquids is slowed during brief intermittent high-intensity exercise compared with rest or steady-state moderate exercise, and the intensity of football match-play is sufficient to slow gastric emptying.

Supplements ante team sport performance

Like most athletes, team sport athletes are often interested in the potential ergogenic edge that could be gained by means of dietary supplements. Among these supplements, creatine (Cr) is the one that has been investigated the most in relation with team sports, given that its purported ergogenic action (i.e. enhanced recovery of the phosphocreatine power system) matches the activity profile of team sports. Both acute and chronic Cr supplementation may contribute to improved training and competition performance in team sports. Caffeine ingestion can also enhance team sport performance by improving speed, power, intermittent sprint ability, jump performance and passing accuracy. However, conflicting results are not lacking in the literature. Other dietary supplements with a potential but yet unclear ergogenic effect for team sport performance include induced metabolic alkalosis via bicarbonate ingestion and bovine colostrum.

References

  • Abt G Zhou S, Weatherby R. The effect of a high-carbohydrate diet on the skill performance of midfield soccer players after intermittent treadmill exercise. J Sci Med Sport. 1998;1(4):203-12.
  • Balsom PD, Wood K, Olsson P, Ekblom B. Carbohydrate intake and multiple sprint sports: with special reference to football (soccer). Int J Sports Med. 1999;20(1):48-52.
  • Bangsbo J. The physiology of soccer: with special reference to intense intermittent exercise. Acta Physiol Scand. 1994;619:1-155.
  • Burke LM, Hawley JA. Fluid balance in team sports. Guidelines for optimal practices. Sports Med. 1997;24(1):38-54.
  • Clark M, Reed DB, Crouse SF, Armstrong RB. Pre- and post-season dietary intake, body composition, and performance indices of NCAA division I female soccer players. Int J Sport Nutr Exerc Metab. 2003;13(3):303-19.
  • Clarke ND, Drust B, MacLaren DP, Reilly T. Strategies for hydration and energy provision during soccer-specific exercise. Int J Sport Nutr Exerc Metab. 2005;15(6):625-40.
  • Edwards AM, Noakes TD. Dehydration: cause of fatigue or sign of pacing in elite soccer? Sports Med. 2009;39(1):1-13.
  • Garrido G, Webster AL, Chamorro M. Nutritional adequacy of different menu settings in elite Spanish adolescent soccer players. Int J Sport Nutr Exerc Metab. 2007;17(5):421-32.
  • Hawley J, Burke L. Peak Performance: Training and Nutritional Strategies for Sport. St. Leonards, NSW: Allen & Unwin, 1998.
  • Iglesias-Gutiérrez E, García-Rovés PM, Rodríguez C, Braga S, García-Zapico P, Patterson AM. Food habits and nutritional status assessment of adolescent soccer players. A necessary and accurate approach. Can J Appl Physiol. 2005;30(1):18-32.
  • Krustrup P, Mohr M, Steensberg A, Bencke J, Kjaer M, Bangsbo J. Muscle and blood metabolites during a soccer game: implications for sprint performance. Med Sci Sports Exerc. 2006;38(6):1165-74.
  • Little JP, Chilibeck PD, Ciona D, Vandenberg A, Zello GA. The effects of low- and high-glycemic index foods on high-intensity intermittent exercise. Int J Sports Physiol Perform. 2009;4(3):367-80.
  • Maughan RJ, Watson P, Evans GH, Broad N, Shirreffs SM. Water balance and salt losses in competitive football. Int J Sport Nutr Exerc Metab. 2007;17(6):583-94.
  • McGregor, Nicholas, Lakomy, Williams. The influence of intermittent high-intensity shuttle running and fluid ingestion on the performance of a soccer skill. J Sports Sci. 1999;17:895-903.
  • Nicholas CW, Williams C, Lakomy HK, Phillips G, Nowitz A. Influence of ingesting a carbohydrate-electrolyte solution on endurance capacity during intermittent, high-intensity shuttle running. J Sports Sci. 1995;13(4):283-90.
Comparte este contenido
cart linkedin facebook pinterest youtube rss twitter instagram facebook-blank rss-blank linkedin-blank pinterest youtube twitter instagram