EAL

NAP: Competition (2007)

Citation:

Chryssanthopoulos C, Williams C, Nowitz A. Influence of a carbohydrate-electrolyte solution ingested during running on muscle glycogen utilisation in fed humans. Int J Sports Med. 2002; 23 (4): 279-284.

PubMed ID: 12015629

Study Design:

Randomized Crossover Trial

Class:

A - Click here for explanation of classification scheme.

Quality Rating:

NEUTRAL: See Quality Criteria Checklist below.

Research Purpose:

The purpose of this study is to examine whether the ingestion of a carbohydrate electrolyte solution by fed (rather than fasted) runners during exercise contributes to muscle metabolism early in exercise.

Inclusion Criteria:

Males
Recreational or club runners.

Exclusion Criteria:

There were no exclusion criteria noted.

Description of Study Protocol:

Recruitment: Subjects were volunteers
Design: Randomized crossover trial
Blinding used: Blinding was not used.

Intervention

Each subject was required complete two visits, which required them to run for 60 minutes at 70% of VO_2max three hours after the ingestions of a high carbohydrate meal (2.5g per kg body weight). During the run, subjects were given either water or a carbohydrate-electrolyte drink (6.9% CHO solution) at 20 and 40 minutes into the run.

Statistical Analysis

Two-way analysis of variance for repeated measures on two factors (treatment by time) was used to compare cardiovascular changes and metabolic responses to all of the study
The remaining responses were examined using a two-tailed Student's T-test for dependent samples
A Tukey post-hoc test was performed if significant differences were revealed using the ANOVA.

Data Collection Summary:

Timing of Measurements

After a 12-hour fast, a venous blood sample was taken
Thirty minutes prior to the end of the three-hour post-prandial period, nude body mass was taken
Three hours post prandial a venous blood and muscle sample were obtained
Venous blood samples and one-minute expired air samples were collected after 10, 20, 40 and 60 minutes of exercise
Within 15 to 60 seconds post-running, another muscle biopsy was obtained
Nude body mass was measured post-exercise.

Dependent Variables

Hemoglobin: Measured via blood sample
Hematocrit: Measured via blood sample
Blood glucose: Measured via blood sample
Blood lactate: Measured via blood sample
Plasma FFA: Measured via blood sample
Glycerol: Measured via blood sample
Sodium: Measured via blood sample
Potassium: Measured via blood sample
Glycogen: Measured via muscle biopsy
Glucose: Measured via muscle biopsy
G-6-P: Measured via muscle biopsy
ATP: Measured via muscle biopsy
PCr: Measured via muscle biopsy
Creatine: Measured via muscle biopsy.

Independent Variables

6.9% carbohydrate-electrolyte solution at 5ml per kg^-1.

Control Variables

Laboratory conditions
Pre-exercise meal at 183±7g of carbohydrates
Running time (60 minutes) and intensity (70% of VO_2max).

Description of Actual Data Sample:

Initial N: Eight male recreational or club level runners
Attrition (final N): Eight
Age: 33.7±3.1 (25 to 48)
Ethnicity: Not noted.

Other Relevant Demographics

Variable	Value	SEM
Height (cm)	182.8±2.0	169.1 – 180.5
Body Mass (kg)	73.3±2.2	64.6 – 80.4
VO2 (ml/kg/min)	58.7±2.1	49.3 – 66.7
HRmax (beat/min)	193±3	184 – 213

Location: Loughborough University, Loughborough, UK

Summary of Results:

Variables	Meal + Carbohydrate (M+C) Pre-	M+C Post-	Meal + Water (M+W) Pre-	M+W Post-
Glycogen	321.9±27.2	225.8±26.7	338.8±32.8	261±40.5
Glucose	1.5±0.2	1.5±0.2	1.4±0.2	1.4±0.1
G-6-P	1.3±0.1	1.8±0.3	1.1±0.2	2.0±0.2
ATP	28.9±1.5	51.6±0.9	28.8±1.0	28.0±1.1
PCr	75.2±3.0	65.5±2.6	75.2±1.9	68.7±4.0
Creatine	63.0±1.2	45.7±3.6	36.0±3.1	42.6±3.7
Lactate	4.6±0.3	7.4±1.1	5.3±0.7	9.1±1.0

Other Findings

[Muscle glycgoen] were not different between the two trials before or after running for 60 minutes
There was no difference in the amount of muscle glycogen used during exercise
There were no differences in muscle glucose, G-6-P, ATP, PCr, creatine and lactate concentrations before or after the 60-minute treadmill run
Serum insulin concentrations were similar in the two trials
Plasma FFA were 6.4-fold and 4.3-fold lower (P<0.01) at the start of exercise, compared with fasting values, however no difference was found in the plasma FFA between the two trials
Plasma glycerol, serium sodium and serum potassium were all similar in the two trials
Blood glucose concentrations were higher at the end of 60 minutes of running in the M+C trial, compared with the M+W trial (P<0.01)
In the M+W trial, blood glucose concentrations were lower (P<0.01) at 10 minutes and 20 minutes of exercise, respectively, when compared with the values at the start of exercise.

Author Conclusion:

The main finding of this study is that the ingestion of the 6.9% carbohydrate-electrolyte solution by fed runners during a 60-minute treadmill run at 70% of VO_2max did not influence the amount of glycogen used nor the accumulation of glycolytic intermediates.

Funding Source:

University/Hospital:

Loughborough University

Reviewer Comments:

Inclusion and exclusion criteria and recruitment methods were not well-defined
This study suggests that a sub-maximal exercise bout lasting longer than 60 minutes may not be enhanced by the ingestion of a carbohydrate-electrolyte solution secondary to the fuel that is mobilized. The subjects in this study were fed, therefore a carbohydrate-electrolyte solution given in a fasted state may have a different metabolic and performance outcome.
We must be careful to compare research that is complete in similar states (fed vs. fasted).

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?	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?	???
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?		No
	5.1.	In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate?	No
	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?		???
	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?	No
	8.7.	If negative findings, was a power calculation reported to address type 2 error?	No
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