Participants
This study was part of a larger investigation examining the effects of CHO ingestion and CHO mouth rinsing [23] and the perceptual and mood data will be presented here. Nine male cyclists and triathletes (age 32.7 ± 13.0 y, height 1.80 ± 0.05 m, body mass 72.7 ± 7.3 kg and peak oxygen uptake (\( \overset{.}{\mathrm{V}}{\mathrm{O}}_2 \) peak) 55.1 ± 7.6 mL · kg−1 · min−1; mean ± SD) volunteered to participate in this study. They were moderately trained athletes undertaking 5 to 20 h per week of training, interspersed with competitive events. All procedures had prior approval by the Massey University Human Ethics Committee (Southern A 10/01). All participants completed a medical history screening questionnaire and provided written informed consent prior to participation.
Preliminary measurements
Following anthropometric measurements, participants performed a graded exercise test, on an electronically braked cycle ergometer (model Excalibur, Lode, Groningen, Netherlands), to determine \( \overset{.}{\mathrm{V}}{\mathrm{O}}_2 \) peak [24] and peak power output (Wmax). They then underwent a short familiarisation of the glycogen reduction exercise protocol [25] before undertaking a full familiarisation of the 1-h cycling time trial protocol [26]. During the familiarisation of the 1-h cycling time trial, the participants were introduced to the perceptual measures and the mouth rinse protocol. They were also provided with information on how to complete the 2-day dietary record.
Experimental trials
All participants completed four experimental trials, each separated by 7 days, in an air-conditioned laboratory maintained at 18–20 °C. A counterbalanced trial order was used to offset any potential order effects. Participants were asked to avoid consumption of alcohol and caffeine and to record dietary intake over the 2-day period prior to the first main trial and to replicate their intake prior to the other three trials. Their diets were analysed for total energy intake and relative contributions of macronutrients (FoodWorks 5.0, Xyris Software, Australia). The mean energy (13.1 ± 5.7 MJ, 12.7 ± 5.8 MJ, 12.3 ± 5.5 MJ and 11.8 ± 5.4 MJ) and carbohydrate (845 ± 197 g · day−1, 694 ± 203 g · day−1, 729 ± 195 g · day−1 and 705 ± 178 g · day−1) intake were not different between trials. Each experimental trial took place over 2 days. On the evening of Day 1, the participants completed a glycogen-reducing exercise protocol followed by a low CHO meal and then a subsequent overnight fast; the following morning participants completed a performance time trial ride.
The glycogen reduction exercise was designed to decrease the glycogen content in both type I and type II muscle fibres [25]. This procedure required participants to cycle for 30 min at 70% \( \overset{.}{\mathrm{V}}{\mathrm{O}}_2 \) peak, followed by three 50-s ‘sprints’ at double the resistive load (with 2 min rest between each bout), and then a further 45 min at 70% \( \overset{.}{\mathrm{V}}{\mathrm{O}}_2 \) peak. After completing this exercise participants were provided with a low CHO meal which was the last meal of the day (energy content of 56 kJ · kg−1 body mass and CHO content of 1 g · kg−1 BM) [26]. Thereafter, they were instructed not to consume any other food but were allowed to consume water ad libitum. Participants arrived in the laboratory the following morning after having fasted for 10–12 h.
Upon arrival on the morning of Day 2 participants’ nude body mass was measured and a cannula was inserted into an antecubital vein (kept patent by frequent flushing with sterile saline). Following a 10-mL resting blood sample and a brief warm-up (5 min at 40% Wmax), participants completed the 1-h time trial [27]. Briefly, participants performed a pre-determined amount of work as fast as possible based on the following:
Total work (J) = 0.75 ∙ Wmax ∙ 3600 s
Where the total amount of work (J) performed was calculated by assuming that the participants could cycle at 75% of their maximum power output (Wmax) for 60 min [27]. Power output during the performance trial was self-selected. The changes of power output were recorded by the investigator and the total amount of work to be performed was recalculated based on the power output at that point in time. Participants received no verbal encouragement and no information of performance other than the amount of work completed.
Trial solutions
The four trial solutions included A) carbohydrate mouth rinse (CHOR), B) placebo mouth rinse (PLAR), C) carbohydrate ingestion (CHOI) and D) placebo ingestion (PLAI). In Trial A, a 15% CHO solution was used for rinsing and in Trial C a 7.5% CHO solution was used for ingestion. The higher energy content for the mouth rinse solution was chosen as functional magnetic resonance imaging (fMRI) studies have used similar concentrations and shown changes in brain function and improvements in motor output [28]. The placebo solutions (Trials B and D) were taste and colour matched and contained 0% CHO and artificial sweeteners (aspartame). The solutions had a mandarin flavour, were manufactured on-site at the university’s food technology laboratory and were stored in the laboratory food refrigerator (Fisher and Paykell, c450, New Zealand). Trial solution administration and recipes were produced according to previously established methods [29].
During the ingestion trials 1.5 mL∙kg−1 body mass solutions were consumed using a sipper bottle. The participant was informed to finish the solution when it was given to them. The trial solution was given every 12.5% of exercise completed. During the mouth rinsing trials participants were required to rinse 0.33 mL∙kg−1 body mass solutions (provided in a plastic volumetric syringe; Omnifix 50/60 ml Luer; Germany). Participants self-administered the mouth rinse and were asked to swirl the solution in their mouth for 8 s. After rinsing, participants expectorated all of the solution into a pre-weighed container which was then accurately measured using electronic scales accurate to 0.0001 g (Sartorius LE3235, Germany). The mouth rinse was also administered every 12.5% of exercise completed.
Perceptual measures
A number of perceptual measures were recorded before, during and after the 1-h time trial. The FAS ranges from 1 indicating low arousal/activation characterised by feeling bored, relaxed and/or calm to 6 which indicates high arousal/activation characterised by feeling angry or excited. The FS is an 11-point scale ranging from -5 (feeling very bad) to +5 (feeling very good) with markers in between these points. The RPE scale [30] ranges from 6 (very, very light) to 20 (very, very hard). These measures were administered every 25% of exercise completed. The shortened POMS [31] is an adjective check list consisting of 37 items rated on a 5-point scale that ranges from ‘not at all’ to ‘extremely’; six factors are derived: tension-anxiety, depression-dejection, anger-hostility, fatigue-inertia, vigour-activity and confusion-bewilderment. The questionnaire was used immediately prior to and immediately following the performance test.
Blood dispensing and analysis
Blood was collected at rest and after every 25% of exercise completed during the 1-h time trial. The sample was collected in an EDTA tube and centrifuged at 1500 G (Hanil, MF50, Korea) for 10 min at 4 °C and then placed in a −80 °C freezer (Thermaforma 929, Ohio, USA). Plasma glucose was determined using a hexokinase method (Roche Diagnostics, Basel, Switzerland; Flexor E, Vital Scientific NV, 6956 AV Spankeren/Dieren, The Netherlands).
Statistical analysis
Data were compared using a two-way analysis of variance (ANOVA) with repeated measures (SPSS version 18.0. Chicago, IL) to examine main effects of i) treatment (PLAR, PLAI, CHOR, CHOI) and ii) time (percentage of exercise completed) and iii) interaction of treatment x time. Mauchly’s test for sphericity was applied to the data to examine if sphericity was violated. When sphericity was violated, the Huynh-Feldt estimate was used to correct the data. When significant differences between the interventions were identified by ANOVA, post-hoc Student’s t-test, using the Holm-Bonferroni adjustment, was performed. Correlations between variables were examined using simple linear regression equations and reported as Pearson’s correlation coefficient (r). A small (weak) correlation was defined as ± .10 to ± .29, medium (moderate) correlation as ± .30 to ± .49 and large (strong) as ± .50 to ± 1.00 [32]. Data is presented as means ± SD. Statistical significance was set at P < 0.05.