EAL

NAP: Training (2014)

Citation:

Wong SH, Chan OS, Chen YJ, Hu HL, Lam CW, Chung PK. Effect of pre-exercise glycemic index meal on running when CHO-Electrolyte solution is consumed during exercise. Int J Sport Nutr Exerc Metab. 2009; 19(3): 222-242.

Study Design:

Randomized Crossover Trial

Class:

A - Click here for explanation of classification scheme.

Quality Rating:

NEUTRAL: See Quality Criteria Checklist below.

Research Purpose:

To examine the effect of consuming CHO-electrolyte solution on running performance after different glycemic index (GI) meals.

Inclusion Criteria:

Male runners
Free of diabetes
Weekly running distance at least 50km.

Exclusion Criteria:

Not available.

Description of Study Protocol:

Recruitment

From local long-distance running clubs and university running teams.

Design

Randomized crossover trial after completing two pre-tests and screening of blood glucose response.

Intervention

Meal consumed two hours before run after overnight fast:

Low-GI: 35.9 GI, 15.7 glycemic load, 61% CHO, 14% PRO, 25% fat, 1.5g per kg CHO
High-GI: 82.9 GI, 68.1 glycemic load, 61% CHO, 14% PRO, 25% fat, 1.5g per kg CHO
Control: Zero GI, zero glycemic load, 0g CHO, 3g PRO, 0g fat
Water standardized (1,100ml fluid)
6.6% CHO-E solution (2ml per kg) given before exercise and every 2.5kg throughout run.

Statistical Analysis

One-way ANOVA with Tukey's post-hoc test to compare dependent variables of the three trials
Two-way Tx X time ANOVA with repeated measures to look at physiological and performance changes.

Data Collection Summary:

Timing of Measurements

After a overnight fast, baseline blood samples collected. One of three meals consumed two hours prior to 21km running bout (randomized counterbalanced order). During those two hours after eating, blood glucose and perceived ratings of gut fullness were recorded. After two hours, a five-minute warm-up was followed by a 21km run (70% VO_2max for first 5km, then ad lib for the rest of the trial).

Dependent Variables

Heart rate
CHO and fat oxidation rates
Blood glucose and lactate
Insulin, FFA and glycerol
HCT, Hgb
Plasma Na and K
Run time to completion.

Independent Variables

GI meal condition (Low, High, Control).

Control Variables

Overnight fasting prior to trials
Timing of measurements
Subjects maintained their same training schedule outside of the lab, as well as dietary intake pre-trial.

Description of Actual Data Sample:

Initial N: Nine male endurance runners
Age: 24±2.4 years
Ethnicity: Not given, but assumed Asian given the study location
Other relevant demographics: VO_2max 58.4±1.5ml per kg per minute.

Anthropometrics

Body mass: 62.0±1.5kg
Percent BF 8.6±0.4%.

Location

Hong Kong.

Summary of Results:

Key Findings

Pre-exercise: Blood glucose response was highest for hi-GI condition, and peaked at 30 minutes. There was no difference in post-prandial blood lactate between conditions. Serum insulin rose after the low-GI or Hi-GI meal vs. the control and peaked at 60 minute for both trials. A greater changes was seen for the Hi-GI vs. the other two trials. FFA were no different between hi-GI and lo-GI meals, and was higher at 60 minutes and 120 minutes in the control than the other two trials.
During exercise: Blood osmolality was higher than pre-meal levels, but no differences between trials were observed
Greater satiety was shown for the lo-GI meal
There were no differences in time to complete the 21km run, nor were there differences in CHO and fat oxidation throughout the trials, despite differences in pre-exercise blood glucose, serum insulin and serum FFA.

Author Conclusion:

When a CHO-E solution (0.8g CHO per minute) was consumed during the 21km run, performance time and metabolic changes during exercise were similar, irrespective of whether a hi-GI or lo-GI pre-exercise meal was consumed.

Funding Source:

Other:

Reviewer Comments:

Quality Criteria Checklist: Primary Research
Relevance Questions
	1.	Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies)	Yes
	2.	Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about?	Yes
	3.	Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice?	Yes
	4.	Is the intervention or procedure feasible? (NA for some epidemiological studies)	Yes

Validity Questions
1.	Was the research question clearly stated?		Yes
	1.1.	Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified?	Yes
	1.2.	Was (were) the outcome(s) [dependent variable(s)] clearly indicated?	Yes
	1.3.	Were the target population and setting specified?	Yes
2.	Was the selection of study subjects/patients free from bias?		???
	2.1.	Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study?	No
	2.2.	Were criteria applied equally to all study groups?	N/A
	2.3.	Were health, demographics, and other characteristics of subjects described?	Yes
	2.4.	Were the subjects/patients a representative sample of the relevant population?	???
3.	Were study groups comparable?		Yes
	3.1.	Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT)	Yes
	3.2.	Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?	Yes
	3.3.	Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.)	Yes
	3.4.	If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis?	N/A
	3.5.	If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.)	N/A
	3.6.	If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")?	N/A
4.	Was method of handling withdrawals described?		Yes
	4.1.	Were follow-up methods described and the same for all groups?	N/A
	4.2.	Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.)	N/A
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	Yes
	4.4.	Were reasons for withdrawals similar across groups?	N/A
	4.5.	If diagnostic test, was decision to perform reference test not dependent on results of test under study?	N/A
5.	Was blinding used to prevent introduction of bias?		N/A
	5.1.	In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate?	Yes
	5.2.	Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.)	Yes
	5.3.	In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded?	N/A
	5.4.	In case control study, was case definition explicit and case ascertainment not influenced by exposure status?	N/A
	5.5.	In diagnostic study, were test results blinded to patient history and other test results?	N/A
6.	Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described?		Yes
	6.1.	In RCT or other intervention trial, were protocols described for all regimens studied?	Yes
	6.2.	In observational study, were interventions, study settings, and clinicians/provider described?	N/A
	6.3.	Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect?	Yes
	6.4.	Was the amount of exposure and, if relevant, subject/patient compliance measured?	Yes
	6.5.	Were co-interventions (e.g., ancillary treatments, other therapies) described?	N/A
	6.6.	Were extra or unplanned treatments described?	N/A
	6.7.	Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups?	Yes
	6.8.	In diagnostic study, were details of test administration and replication sufficient?	Yes
7.	Were outcomes clearly defined and the measurements valid and reliable?		Yes
	7.1.	Were primary and secondary endpoints described and relevant to the question?	Yes
	7.2.	Were nutrition measures appropriate to question and outcomes of concern?	Yes
	7.3.	Was the period of follow-up long enough for important outcome(s) to occur?	Yes
	7.4.	Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures?	Yes
	7.5.	Was the measurement of effect at an appropriate level of precision?	Yes
	7.6.	Were other factors accounted for (measured) that could affect outcomes?	Yes
	7.7.	Were the measurements conducted consistently across groups?	Yes
8.	Was the statistical analysis appropriate for the study design and type of outcome indicators?		Yes
	8.1.	Were statistical analyses adequately described and the results reported appropriately?	Yes
	8.2.	Were correct statistical tests used and assumptions of test not violated?	Yes
	8.3.	Were statistics reported with levels of significance and/or confidence intervals?	Yes
	8.4.	Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)?	N/A
	8.5.	Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)?	N/A
	8.6.	Was clinical significance as well as statistical significance reported?	Yes
	8.7.	If negative findings, was a power calculation reported to address type 2 error?	N/A
9.	Are conclusions supported by results with biases and limitations taken into consideration?		Yes
	9.1.	Is there a discussion of findings?	Yes
	9.2.	Are biases and study limitations identified and discussed?	Yes
10.	Is bias due to study's funding or sponsorship unlikely?		???
	10.1.	Were sources of funding and investigators' affiliations described?	No
	10.2.	Was the study free from apparent conflict of interest?	???