EAL

NAP: Training (2014)

Citation:

Chen YJ, Wong SHS, Chan COW, Wong CK, Lam CW, Siu PMF. Effects of glycemic index meal and CHO-electrolyte drink on cytokine response and run performance in endurance athletes. J Sci Med Sport. 2009; 12: 697-703.

Study Design:

Randomized Crossover Trial

Class:

A - Click here for explanation of classification scheme.

Quality Rating:

POSITIVE: See Quality Criteria Checklist below.

Research Purpose:

To evaluate if the pre-exercise glycemic index (GI) meal, when carbohydrate electrolyte (CHO-E) solution was consumed during exercise, would influence the subsequent endurance run performance and some cytokines and interleukin-2 (IL-2) secretion during the short-term recovery from a 21km run.

Inclusion Criteria:

Healthy
Endurance trained male runners.

Exclusion Criteria:

History of diabetes mellitus.

Description of Study Protocol:

Design

Before-after study.

Intervention

Pre-exercise meals: Two isocaloric GI meals (1.5g CHO per kg body mass; 62.1% CHO, 14.1% PRO, 24.7% Fat) with a low GI (LGI) meal of 36 and a high GI (HGI) meal of 83; and a control fat-free, sugar-free meal (36kcal, gelatin)
CHO-E drink: A drink with 6.6% glucose (26kcal, 6.6g CHO, 49mg Na, 20mg K, 2 g Ca, 0.6mg Mg per 100ml)
Prior to exercise and every 2.5km, the subjects drank 2ml per kg^-1 BM of 6.6% CHO-E solution for a total of approximately 74g CHO for the 21km run. Only distilled water was allowed during one hour after exercise.

Statistical Analysis

Two-factor trial (trial x time) repeated measures analysis of variance (ANOVA). Significant F ratios were assessed using a post-hoc Tukey test. If a data set was not normally distributed, statistical analysis was performed on the logarithmic transformation of the data. Assumptions of homogeneity and sphericity in the data were checked and adjustment in the degrees of freedom for the ANOVA was made when necessary. Performance times were analyzed using the Wilcoxon signed ranks tests for nonparametric data.

Data Collection Summary:

Timing of Measurements

Baseline and 15, 30, 45, 60, 90 and 120 minutes after each of the three meals for blood glucose. Other blood, expired air collection heart rate at pre-meal (PRE-2h), pre-exercise, immediately (POST), and one hour after exercise (POST-60 min).

Dependent Variables

Blood samples for glucose, insulin, cortisol, hematocrit, hemoglobin, cytokines, IL-6, IL-2, and TNF-a: After a 12-hour fast for baseline
Expired air collection: VO_2max: Five-minute warm-up at 60% VO_2maxafter a two-hour rest. For the first 5km, the subjects ran on a treadmill at a fixed speed of 70% VO_{2max_.}. They could then change their running speed ad libitum over the remaining distance of the entire 21km performance.
Diet: Three-day food diary was analyzed and subjects were required to repeat the same diet the next two trials. A food diary was kept during the three days prior to each trial.

Independent Variables

Pre-exercise meal (high GI vs. low GI vs. control).

Control Variables

Pre-trial diet: Three-day food diary was analyzed and subjects were required to repeat the same diet the next two trials
Standardized exercise protocol
Standardized CHO-E solution consumption.

Description of Actual Data Sample:

Initial N: Eight males
Attrition (final N): Eight
Age: 28.6±2.7 years.

Anthropometrics

Body mass: 61.9±1.71kg
VO₂ _max: 58.8±1.6ml per kg^-1 per minute^-1.

Location

Hong Kong.

Summary of Results:

Findings

There were no differences in time to complete the 21km run between LGI and HGI. Performance was improved on HGI when compared with that on control (CON) (91.5±2.2 minutes vs. 93.6±2.1 minutes, P<0.05).
There were no differences in the daily energy intake and the macronutrient composition of the subjects' diet during the three days before each trial, P>0.05
No significant response of TNF-a after exercise could be detected in all three trials. The IL-2 decreased at POST on CON only (pre-exercise vs. POST: 67.6±2.2pg per ml^-1 vs. 54.5±1.7pg per ml^-1, P<0.001). The IL-2 returned to normal at POST-60 minutes in all trials.
The IL-6 increased by more than 100 times; the mean value ranged from 0.70pg per ml^-¹at PRE-ex at 82.09pg per ml^-¹at POST in the three trials. It returned to the level at PRE-ex only on LGI at POST-60 minutes.
The two-hour incremental area under the blood glucose curve after ingestion of the HGI was nearly four times larger than that in LGI (P<0.01). Blood glucose in LGI were similar throughout exercise except at 21km (POST, P<0.01). Blood glucose on HGI during exercise were improved from pre-exercise (P<0.01). For CON, blood glucose was different from pre-exercise at 5km, 10km and 21km (P<0.05). Among the three trials, only the glucose in HGI (P<0.05) did not return to pre-meal level at POST-60 minute
Serum insulin increased after the GI meals and peaked at 60 minutes in both trials (P<0.01). There were differences among the three trials in the two hours post-prandial period (P<0.01). No differences were found in insulin during exercise and post-exercise among the three trials.
There were no differences in CHO and fat oxidation rate, total amounts of CHO and fat oxidized at rest and during exercise among trials. The CHO oxidation rates during exercise were greater than that in the two-hour post-prandial period (P<0.01) and peaked at 5km for all trials. The fat oxidation rates 10km, 15km and 21km were higher than in the two-hour post-prandial period (P<0.01) and peaked at 21km for all trials.
An increasing trend of serum cortisol was seen after the onset of exercise in all trials. No difference was found among the trials throughout the exercise period. Compared to the pre-exercise, serum cortisol was higher at 21km in CON and HGI (P<0.01), while at 15km and 21km it was higher in LGI (P<0.01). Cortisol was lower in the LGI (P<0.05) compared with that in CON at POST-60 minutes.

Author Conclusion:

High GI and low GI demonstrated similar performance when CHO-E solution was consumed during a 21km run. However, pre-exercise LGI meal attenuated the increases in cortisol and quickened the recovery of the increased IL-6 value compared to the control meal.

Funding Source:

Reviewer Comments:

Abbreviations like BM and TT are not defined. Unable to determine what TT stands for.

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?		Yes
	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?	Yes
	2.2.	Were criteria applied equally to all study groups?	Yes
	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?	Yes
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?	Yes
	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?		No
	5.1.	In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate?	N/A
	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.)	N/A
	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?	N/A
	6.8.	In diagnostic study, were details of test administration and replication sufficient?	N/A
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?	N/A
	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?		Yes
	10.1.	Were sources of funding and investigators' affiliations described?	Yes
	10.2.	Was the study free from apparent conflict of interest?	Yes