Overzichtsartikel Dietary Supplements to Improve Energy Metabolism During Long-Track Speed Skating Dionne A. Noordhof PhD Abstract The specific skating posture results in blood flow restriction in the legs, which diminishes the relative contribution of the aerobic energy system and increases the contribution of anaerobic energy systems. The purpose of this review was to summarize dietary supplements that might positively affect anaerobic energy metabolism and gross efficiency in speed skating, and to discuss the effects of these supplements on performance. Creatine, β-alanine, and sodium bicarbonate are supplements that might positively affect anaerobic energy metabolism, and dietary nitrate might influence efficiency. Based on the reviewed literature, it can be concluded that the acute effect of creatine seems trivial, but that chronic supplementation seems beneficial. Acute sodium bicarbonate supplementation is expected to result in moderate performance enhancements. Combining chronic β-alanine supplementation with acute sodium bicarbonate supplementation might have additive effects. The effectiveness of chronic β-alanine supplementation, chronic sodium bicarbonate, and acute or chronic dietary nitrate supplementation requires further investigation. Keywords: nutrition, ergogenic aids, performance Trefwoorden: voeding, prestatiebevorderende middelen, prestatie Introduction Speed skating performances have improved considerably over the last 50 years. Model calculations showed that about half of this performance improvement could be ascribed to technological innovations and the other half to athletic improvement.1 Athletic improvement can be realized by increasing the total metabolic energy produced or by reducing power losses, as mechanical power output or speed is the result of the dynamic balance between metabolic power production and power losses due to friction.2,3 When the power losses are disregarded, a performance improvement can be realized by an increase in metabolic energy production. There are three main physiological factors that determine metabolic power production: 1) performance VO2 , 2) performance O2 6 Sport & Geneeskunde | november 2015 | nummer 3 deficit (anaerobic capacity), and 3) the gross mechanical efficiency (Figure 1).4 Therefore, dietary supplements that might positively affect energy metabolism, are supplements that affect one or more of these physiological factors. As sport nutrition knowledge and the dietary supplement industry have evolved enormously over the last 50 years, it seems reasonable that sports nutrition (including dietary supplements) nowadays has a larger contribution to performance than 50 years ago, which may explain a small part of the athletic improvement. Races of elite senior long-track speed skaters over 500 to 10,000 m result in finish times between 34.03 s (current world record 500 m men) and about 14 min.5 perform these exercise tasks, the To body continually needs chemical energy, which is derived from high-energy phosphate compounds, predominantly phosphocreatine and adenosine triphosphate. To continuously resynthesize high-energy phosphate compounds both anaerobic and aerobic energy systems are important. The specific speed skating technique is characterized by a deeply crouched position (Figure 2). ISU World Cup contestants showed an average pre-extension knee angle of 105.9 ± 5.2 and 111.4 ± 5.3° and an average trunk angle of 14.1 ± 4.8 and 15.2 ± 3.4° during the first complete lap of a 1500 and 5000 m, respectively.6 The small knee angle and low trunk position, shown by elite speed skaters, results in a reduced cardiac output and lower peak oxygen consumption (VO2peak ) than during cycling7 and running.8 Besides, Pagina 5
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Sport & Geneeskunde nummer 3 | november 2015 Lees publicatie 52Home