EAL

NAP: Competition (2007)

Citation:

Nassis GP, Williams C, Chisnall P. Effect of a carbohydrate-electrolyte drink on endurance capacity during prolonged intermittent high intensity running. Br J Sports Med. 1998; 32: 248-252.

PubMed ID: 9773176

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 investigate the influence of drinking a carbohydrate-electrolyte solution on endurance capacity during prolonged intermittent high-intensity running.

Inclusion Criteria:

All subjects were experienced endurance-trained athletes.

Exclusion Criteria:

None specifically mentioned.

Description of Study Protocol:

Recruitment: Methods not specified
Design: Randomized crossover trial
Blinding used: Double-blind.

Intervention (if applicable)

Subjects ran to exhaustion on a motorized treadmill on two occasions separated by at least 10 days
After an overnight fast, they performed repeated 15-second bouts of fast running (at 80% VO_2max for the first 60 minutes, at 85% VO_2max for 60 until 100 minutes and 90% VO_2max from 100 minutes until exhaustion), separated by 10 seconds of slow running at 45% VO_2max
On each occasion, they drank either a water placebo or a 6.9% carbohydrate-electrolyte solution immediately before the run ( three ml per kg of body mass) and every 20 minutes thereafter (two ml per kg of body mass).

Statistical Analysis

Differences between two trials were examined using Student's T-test for correlated samples
Statistical comparisons of physiological and metabolic parameters were undertaken for the sampling points, where complete data were available, using a two-way ANOVA for repeated measures on two factors (experimental condition and sampling time)
Where significant differences were found, a Tukey test was employed to identify differences.

Data Collection Summary:

Timing of Measurements

Expired air samples were collected for 50 seconds during the last minute of warm-up, every 20 minutes during the run and during the final minute of the run
Blood samples were taken before exercise and after the warm-up, every 20 minutes throughout the run and immediately after the completion of exercise.

Dependent Variables

Expired air samples were collected using a Douglas bag
Blood samples were analyzed for glucose and lactate
Fatigue was measured with a Borg Scale
Sweat rate
Carbohydrate oxidation rate.

Independent Variables

Water placebo or 6.9% carbohydrate-electrolyte solution immediately before the run (three ml per kg of body mass) and every 20 minutes thereafter (two ml per kg of body mass)
Subjects asked to refrain from heavy exercise for two days before each trial
Subjects asked to record their diet for three days prior to trials and follow the same dietary pattern.

Description of Actual Data Sample:

Initial N: Nine subjects, eight men, one woman
Attrition (final N): Nine
Age: Mean, 25±4.3 years
Ethnicity: Not mentioned
Location: United Kingdom.

Summary of Results:

Other Findings

Performance times were not different between trials (112.5±23.3 minutes for placebo, 110.2±21.4 minutes for carbohydrate-electrolyte)
The distances covered during the experimental trials were 25.0±6.4 for placebo and 22.9±9.3km for carbohydrate-electrolyte, differences were not significant
Blood glucose concentration was higher in the carbohydrate trial only at 40 minutes of exercise (4.5±0.6mmol/l for carbohydrate-electrolyte, 3.9±0.3mmol/l for placebo; P<0.05)
There was no difference in the total carbohydrate oxidation rates, oxygen uptake or ratings of perceived exertion between trials.

Author Conclusion:

The main finding of this study is that the ingestion of a 6.9% carbohydrate-electrolyte solution did not improve endurance capacity during prolonged intermittent high-intensity running
Performance times for the carbohydrate-electrolyte and placebo trials were similar even though the runners ingested the equivalent of 30g per hour of carbohydrates throughout the carbohydrate-electrolyte trial. These results suggest that drinking a 6.9% carbohydrate-electrolyte solution during repeated bouts of submaximal intermittent high-intensity running does not delay the onset of fatigue.

Funding Source:

University/Hospital:

Loughborough University (UK)

Reviewer Comments:

Inclusion criteria, exclusion criteria and recruitment methods were not well-defined
No power calculations were done.

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?	???
	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?	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%.)	Yes
	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.)	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?	Yes
	6.6.	Were extra or unplanned treatments described?	Yes
	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?	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?		???
	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?	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