EAL

NAP: Competition (2007)

Citation:

Chryssanthopoulos C, Williams C, Nowitz A, Kotsiopoulou C, and Vleck V. The effect of high carbohydrate meal on endurance running capacity. International Journal of Sport Nutrition and Exercise Metabolism, 2002; (12): 157-171.

PubMed ID: 12187616

Study Design:

Randomized crossover trial

Class:

A - Click here for explanation of classification scheme.

Quality Rating:

POSITIVE: See Quality Criteria Checklist below.

Research Purpose:

The purpose of this study is to determine whether a moderate amount of carbohydrate food ingested three hours before exercise improves endurance running capacity, when compared to running without the meal and with ingestion only of water during exercise
This study also asseses the influence of the pre-exercise meal, combined with ingesting a carbohydrate-electrolyte solution throughout the run, on endurance capacity.

Inclusion Criteria:

Recreational- or club-level runners.

Exclusion Criteria:

Any subjects with medical health problems (via health history questionnaire) were excluded.

Description of Study Protocol:

Recruitment: 10 male recreational or club runners volunteered
Design: Randomized crossover trial
Blinding used: Single-blind; the placebo was made to taste like the carbohydrate-electrolyte drink so that subjects would not know the difference between trials.

Intervention

Each subject was required to run to exhaustion at 70% of VO_2max on a treadmill on three different occasions separated by one week.

On one occasion, a high-carbohydrate meal was consumed three hours prior to exercise and a 6.9% carbohydrate-electrolyte solution was ingested during exercise (M+C)
On another occasion, the high-carbohydrate meal was consumed three hours prior to exercise, but during the run they drank only water (P+W)
On another occasion, subjects drank 10ml per kg of body mass of the placebo solution and during exercise, only drank water (P+W)
Subjects were told that during the three trials, they would ingest the same amount of carbohydrates because the concentration of the liquid parts of the meals would be adjusted to achieve this.

Statistical Analysis

Two-way analysis of variance for repeated measures on two factors (treatment by time) was used to compare coardiovascular and metabolic responses to all trials in the study. The remaining responses were examined using a two-tailed Student's T-test for dependent samples.
When significance was revealed using ANOVA, a Tukey post-hoc test was performed; P<0.05.

Data Collection Summary:

Timing of Measurements:

After a 12-hour overnight fast, subjects arrived at the lab and a pre-prandial blood sample was obtained
A high-carbohydrate meal or a 10ml per kg of body mass placebo solution was consumed
Thirty minutes after consumption of the meal or placebo as well as every hour during the three-hour post-prandial period, venous blood samples were obtained
Immediately prior to exercise, subjects consumed either five ml per kg of body mass of a carbohydrate-electrolyte drink or an equivalent amount of water
During exercise, two ml per kg of body mass ^{was consumed every 20 minutes during exercise.}

Dependent Variables

Endurance running capacity.

Independent Variables

On one occasion, a high-carbohydrate meal was consumed three hours prior to exercise and a 6.9% carbohydrate-electrolyte solution was ingested during exercise (M+C)
On another occasion, the high-carbohydrate meal was consumed three hours prior to exercise, but during the run they drank only water (P+W)
On another occasion, subjects drank 10ml per kg of body mass of placebo solution and during exercise only drank water (P+W).

Description of Actual Data Sample:

Initial N: 10 males
Attrition (final N): 10 males
Age: 30.1±3.4 years
Ethnicity: Not noted.

Other Relevant Anthropometrics

Variable	Value
Height (cm)	176.9±2.6
Body Mass (kg)	73.1±4.0
VO_2max (mlkg-1ml-1)	63.5±2.3
Heart Rate (beats per minute)	186±4

Location: Loughborough, UK.

Summary of Results:

Variables	0 Minutes	30 Minutes	60 Minutes	120 Minutes	180 Minutes
Blood Glucose M+C M+W P+W	4.1±0.1 4.1±0.1 4.1±0.1	4.1±0.3 4.4±0.3 3.9±0.1	4.0±0.2 4.7±0.4 4.1±0.1	4.0±0.2 4.7±0.3 4.1±0.2	3.5±0.2 4.0±0.3 4.1±0.1
Blood Lactate M+C M+W P+W	1.0±0.1 0.9±0.1 0.8±0.1	1.9±0.1^a,b 1.6±0.1^a,b 0.9±0.1	1.3 +0.1^a,b 1.2±0.1^a,b 0.9±0.1	1.3±0.1^c 1.2±0.1 0.9± 0.1	1.3±0.3^c 1.0±0.1 0.09±0.1
Serum Insulin M+C M+W P+W	6.6±1.1 6.3±0.7 6.9±1.1	58.7±11.2^a,b 55.1±7.3^a,b 6.4±1.1	41.7±7.1^a,b 47.7±4.6^a,b 8.4±1.1	41.7±7.0^a,b 47.7±7.9^a,b 8.4±2.7	17.4±1.5 22.9±4.4 6.2±0.9
Plasma FFA (N=9) M+C M+W P+W	0.4±0.1 0.4±0.1 0.3±0.1	0.1±0.03^a,b 0.1±0.06^a,b 0.1±0.05	0.08±0.02^a,b 0.06±0.01^a,b 0.4±0.05	0.08±0.02^a,b 0.06±0.01^a,b 0.4±0.07	0.09±0.02^a,b 0.09±0.02^a,b 0.5±0.08
Plasma Glycerol (N=9) M+C M+W P+W	0.09±0.01 0.08±0.01 0.08±0.01	0.05±0.01^a 0.05±0.01^a 0.06±0.01	0.03±0.01^a 0.03±0.01^a 0.07±0.01	0.03±0.01^a,b 0.03±0.01^a,b 0.07±0.01	0.05±0.01^a,b 0.04±0.01^a,b 0.09±0.01

M+C (Meal+Carb Drink)
M+W (Meal+Water)
P+W (Placebo+Water).

[Note on the chart above: P^a<0.01 from zero minutes; P^b<0.01 from P+W; P^c<0.05 from P+W.]

Other Findings

Sensations of fullness were higher (P<0.01) in both meal trials, compared with P+W trial
Abdominal discomfort was not different between conditions
Time to exhaustion was significantly different between M+C and P+W (P<0.01) and between M+W and P+W (P<0.05)
Carbohydrate oxidation rate was higher (P<0.01) in the two meal trials, compared with the P+W trial during the first hour of exercise.

Variable	M+C	M+W	P+W
Endurance capacity (minutes)	125.1±5.3	111.9±5.6	102.9±7.9
Heart rate (beats per minute)	164±2	165±2	168±5.3
RPE	12.3±0.3	12.9±0.5	13.6±0.06

Author Conclusion:

The main finding was that the consumption of a meal three hours prior to exercise, with water ingested during exercise, improved endurance running capacity by 9%. When a meal was consumed three hours prior and a 6.9% carbohydrate-electrolyte drink was consumed during the exercise bout, endruance running capacity improved by 22% (both in comparison to P+W).
Carbohydrate oxidation rates were higher during the first hour in the M+C and M+W groups, therefore suggesting a greater reliance on carbohydrate metabolism for fuel mobilization
In summary, the results of this study show that the consumption of a meal containing a moderate amount of carbohydrates (2.5mg per kg of body mass), three hours before exercise at 70% of VO_2max, improves endurance running capacity. Moreover, the addition of a carbohydrate-electrolyte drink further improves endurance-running capacity.

Funding Source:

University/Hospital:

Loughborough University

Reviewer Comments:

Subjects were well-controlled and carbohydrate was ingested based on body weight. Furthermore, they were told each time that they were ingesting the same amount of carbohydrates.
Additional research has suggested that there may be a placebo effect when subjects are told they are given carbohydrates during exercise, which results in enhanced performance secondary to the belief they are consuming a carbohydrate-electrolyte drink.

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?	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?		Yes
	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.)	No
	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?	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?	N/A
	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)?	???
	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?	No
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