The ingestion of protein with a maltodextrin and fructose beverage on substrate utilisation and exercise performance

Abstract

The study investigated the ingestion of maltodextrin, fructose, and protein on exogenous carbohydrate oxidation (CHOEXO) and exercise performance. Seven trained cyclists and (or) triathletes (maximal oxygen consumption, 59.20 ± 9.00 mL · kg(-1) · min(-1)) performed 3 exercise trials that consisted of 150 min of cycling at 50% maximal power output (160 ± 11 W), followed by a 60-km time trial. One of 3 beverages were randomly assigned during each trial and consumed at 15-min intervals: (i) 0.84 g · min(-1) maltodextrin + 0.52 g · min(-1) fructose + 0.34 g · min(-1) protein (MD+F+P); (ii) 1.10 g · min(-1) maltodextrin + 0.60 g · min(-1) fructose (MD+F); or (iii) 1.70 g · min(-1) maltodextrin (MD). CHO(EXO) and fuel utilisation were assessed via measurement of expired air (13)C content and indirect calorimetry, respectively. Mean total CHO oxidation (CHOTOT) rates were 2.35 ± 0.18, 2.76 ± 0.08, and 2.61 ± 0.17 g · min(-1) with MD, MD+F, and MD+F+P, respectively, although not significantly different. Peak CHO(EXO) rates with MD+F were significantly greater by 41.4% (p = 0.001) and 45.4% (p = 0.0001) compared with MD+F+P and MD, respectively (1.57 ± 0.22 g · min(-1), 1.11 ± 0.08 g · min(-1), and 1.08 ± 0.11 g · min(-1), respectively). Performance times were 2.2% and 5.0% faster with MD+F compared with MD+F+P and MD, respectively; however, they were not statistically significant. Ingestion of an MD-fructose-protein commercial sports beverage significantly reduced peak and mean CHO(EXO) rates compared with MD+F, but did not significantly influence CHOTOT. The addition of protein to an MD+F beverage did not enhance performance times.

Multiple Transportable Carbohydrates During Exercise

“…Three additional studies found performance improvements as large as 7-8% for TT completion with glucose-fructose feedings relative to glucose-only feedings (11,50,63). Multiple transportable carbohydrates reduced GI complaints in several studies, including stomach fullness (31,39,50), nausea (40,50,62), abdominal cramps (40,53,62), and the urge to defecate (50). Two studies support the notion that fluid delivery is more rapid with glucose-fructose mixtures (30,50), whereas another suggests that decreases in plasma volume may be minimized (55).…”

“…In terms of performance, MTC improved outcomes (e.g., completion time, exercise capacity, and power output) in 8 studies (3,11,39,40,53,59,62,63). The largest effect on performance was from the study by Stannard et al (59), in which 1.0 g$min 21 of galactose led to ;15% slower time trial (TT) completion compared with glucose-galactose and glucosefructose mixtures.…”

“…Sample sizes have generally been small, with only 3 studies reporting samples of 15 or greater (35,44,53). Despite the often small sample sizes, statistical power analyses or sample size calculations were undertaken for only 9 studies (3,10,30,35,40,50,53,62,65). Of the 27 studies, 25 were conducted within a laboratory environment, whereas 2 were conducted under field conditions (44,53).…”

“…In nonsimulated events, athletes rarely consume fluid at $1,000 ml$h 21 , even while cycling (45,52). Eight studies (26,30,34,39,50,55,62,63) provided fluid at $1,000 ml$h 21 , which is important to consider because athletes naturally limit fluid intake to minimize GI distress. In addition, the carbohydrate concentration of experimental solutions was at least 10% in 16 studies (1,3,11,(23)(24)(25)27,31,34,36,39,40,50,53,63,65).…”

“…Although the first of these studies focused on exogenous carbohydrate oxidation (1,64), subsequent work demonstrated improvements in endurance performance (11,29). Furthermore, several studies have shown that the risk of gastrointestinal (GI) distress is minimized when multiple saccharides are consumed (31,39,40,53,62). Research regarding the benefits of ingesting multiple saccharides during exercisereferred to as multiple transportable carbohydrates (MTC)has been an exciting advancement in the field of sport nutrition, and these findings have been used by food manufacturers to market products as containing a superior blend of carbohydrate for performance and GI function (17,47).…”