The Effect of Double – Blind Carbohydrate Ingestion during 60 km of Self-Paced Exercise in Warm Ambient Conditions

Abstract

This study evaluated double blind ingestions of placebo (PLA) versus 6% carbohydrate (CHO) either as capsules (c) or beverage (b) during 60 km self-paced cycling in the heat (32°C and 50% relative humidity). Ten well-trained males (mean ± SD: 26±3 years; 64.5±7.7 kg and 70.7±8.8 ml.kg−1.min−1 maximal oxygen consumption) completed four separate 60 km time trials (TT) punctuated by 1 km sprints (14, 29, 44, 59 km) whilst ingesting either PLAb or PLAc or CHOb or CHOc. The TT was not different among treatments (PLAb 130.2±11.2 min, CHOb 140.5±18.1 min, PLAc 143.1±29.2 min, CHOc 137.3±20.1 min; P>0.05). Effect size (Cohen’s d) for time was only moderate when comparing CHOb – PLAb (d = 0.68) and PLAb – PLAc (d = 0.57) whereas all other ES were ‘trivial’ to ‘small’. Mean speed throughout the trial was significantly higher for PLAb only (P<0.05). Power output was only different (P<0.05) between the sprints and low intensity efforts within and across conditions. Core and mean skin temperatures were similar among trials. We conclude that CHO ingestion is of little or no benefit as a beverage compared with placebo during 60 km TT in the heat.

A systematic review and meta-analysis of carbohydrate benefits associated with randomized controlled competition-based performance trials

“…In addition, with the exception of References [ 29 ] and [ 34 ], all trials were performed with male volunteers hampering transfer of results to female athletes. Following conversion of absolute values into percentage data, results were widely spread yielding improvements in assessed outcomes between 0.2 % [ 45 ] –13 % [ 13 ] as well as declines ranging between −0.6 % [ 22 ] and −7.3 % [ 41 ], respectively. This may serve as a potential indicator for the heterogeneous study designs.…”

Meta-Analysis of Carbohydrate Solution Intake during Prolonged Exercise in Adults: From the Last 45+ Years’ Perspective

“…Furthermore, the Egger's test of the intercept and inspection of the funnel plot suggested no potential publication bias (Figure S16). Forest plot shows the effects (red square symbol) of experimental carbohydrate supplementation as compared to a control on exercise outcome for 112 interventions [49][50][51][52][53]78,[80][81][82][83][84][85][86][87][88][89][90][91][92][94][95][96][97][98][99][100][101][102][103][104][105][106][107]109,110,[112][113][114][115][117][118][119]122,124,[129][130][131]…”

“…Figure 3.Forest plot shows the effects (red square symbol) of experimental carbohydrate supplementation as compared to a control on exercise outcome for 127 interventions[47][48][49][50][51][52][54][55][56][57][58][59][60][61][62][63][64][65][67][68][69][70][71][72][73][74][109][110][111][112][113][114][115][116][117][118][120][121][122][123][125][126][127][128][129]131,[133][134][135][136]…”

Sago supplementation for exercise performed in a thermally stressful environment: Rationale, efficacy and opportunity

“…However, in the immediately proceeding work-dependent time-trial both fluid and CHO independently (6%) improved performance compared to a placebo, and the combined effects were additive (12%). While other self-paced cycling protocols have demonstrated that CHO supplementation during exercise heat stress improves performance, 31 at least one report 32 indicates that when double-blinded, CHO supplementation during exercise in the heat does not improve performance. Nevertheless, a neural or psychological effect may be present; an idea borne out from the results of carbohydrate mouth-rinse studies, some of which do suggest a change in brain activity with simply a sweet taste in the mouth 33 …”