Composite versus single transportable carbohydrate solution enhances race and laboratory cycling performance

Abstract

When ingested at high rates (1.8-2.4 g·min(-1)) in concentrated solutions, carbohydrates absorbed by multiple (e.g., fructose and glucose) vs. single intestinal transporters can increase exogenous carbohydrate oxidation and endurance performance, but their effect when ingested at lower, more realistic, rates during intermittent high-intensity endurance competition and trials is unknown. Trained cyclists participated in two independent randomized crossover investigations comprising mountain-bike races (average 141 min; n = 10) and laboratory trials (94-min high-intensity intervals followed by 10 maximal sprints; n = 16). Solutions ingested during exercise contained electrolytes and fructose + maltodextrin or glucose + maltodextrin in 1:2 ratio ingested, on average, at 1.2 g carbohydrate·kg(-1)·h(-1). Exertion, muscle fatigue, and gastrointestinal discomfort were recorded. Data were analysed using mixed models with gastrointestinal discomfort as a mechanism covariate; inferences were made against substantiveness thresholds (1.2% for performance) and standardized difference. The fructose-maltodextrin solution substantially reduced race time (-1.8%; 90% confidence interval = ±1.8%) and abdominal cramps (-8.1 on a 0-100 scale; ±6.6). After accounting for gastrointestinal discomfort, the effect of the fructose-maltodextrin solution on lap time was reduced (-1.1%; ±2.4%), suggesting that gastrointestinal discomfort explained part of the effect of fructose-maltodextrin on performance. In the laboratory, mean sprint power was enhanced (1.4%; ±0.8%) with fructose-maltodextrin, but the effect on peak power was unclear (0.7%; ±1.5%). Adjusting out gastrointestinal discomfort augmented the fructose-maltodextrin effect on mean (2.6%; ±1.9%) and peak (2.5%; ±3.0%) power. Ingestion of multiple transportable vs. single transportable carbohydrates enhanced mountain-bike race and high-intensity laboratory cycling performance, with inconsistent but not irreconcilable effects of gut discomfort as a possible mediating mechanism.

Mixed drink increased carbohydrate oxidation but not performance during a 40 km time trial

“…In contrast to previous research, [7,8,10,15] no improvement in performance was recorded during a 40 km laboratory time trial between the GP and the mixed drinks (p=0.289). Triplett et al [8] showed an 8.1% improvement in time trial performance when participants ingested approximately 144 g (or 2.4 g/min) of drinks containing either GP only, or a GP and fructose (1:1 ratio) mixed drink.…”

“…Similarly, O'Brien and Rowlands [9] have shown that higher rates of exogenous carbohydrate oxidation with a multiple carbohydrate drink result in an improvement in performance over and above that of when an isocaloric single carbohydrate with concomitant lower oxidation rate is ingested. Furthermore, the studies by Rowlands et al [10] and Currell and Jeukendrup [7] measured endogenous a carbohydrate oxidation rates in addition to performance parameters, however, exogenous oxidation rates were not measured and it was assumed that the oxidation rate of the multiple CHO drink ingested was higher.The present study aimed to determine if a superior performance is attained when a multiple carbohydrate drink is ingested. Specifically, time trial performances were compared in a single group of highly trained cyclists to determine whether a multiple carbohydrate drink (glucose: fructose in a 2:1 ratio) confers a performance advantage over that of a single carbohydrate drink (glucose-polymer only), the physiological parameters of lactate, insulin and glucose concentrations, substrate oxidation (total, endogenous and exogenous) and respiratory exchange, will be measured, which may explain the underlying mechanisms that relate to any performance differences.…”

“…Similarly, O'Brien and Rowlands [9] have shown that higher rates of exogenous carbohydrate oxidation with a multiple carbohydrate drink result in an improvement in performance over and above that of when an isocaloric single carbohydrate with concomitant lower oxidation rate is ingested. Furthermore, the studies by Rowlands et al [10] and Currell and Jeukendrup [7] measured endogenous a carbohydrate oxidation rates in addition to performance parameters, however, exogenous oxidation rates were not measured and it was assumed that the oxidation rate of the multiple CHO drink ingested was higher.…”

Is There a Specific Role for Sucrose in Sports and Exercise Performance?

“…Several recent studies have demonstrated the superiority of multiple versus single transportable carbohydrates for prolonged endurance exercise performance when carbohydrate is consumed in large quantities (Currell & Jeukendrup, 2008;Rowlands et al, 2012;Triplett et al, 2010). Undoubtedly, some of the benefit of ingesting multiple transportable carbohydrates can be attributed to increased exogenous fuel provision during exercise as compared with single transportable carbohydrates.…”

“…Undoubtedly, some of the benefit of ingesting multiple transportable carbohydrates can be attributed to increased exogenous fuel provision during exercise as compared with single transportable carbohydrates. In addition, improved gastro-intestinal comfort with multiple transportable carbohydrates has been identified as a possible mediating mechanism in explaining the endurance performance benefits of multiple over single transportable carbohydrates (Rowlands et al, 2012). This is perhaps not surprising given the use of highly concentrated-hypertonic glucose-only control solutions which can demonstrably induce severe gastro-intestinal distress during prolonged exercise (Triplett et al, 2010).…”