NAP: Competition (2007)

Citation:

Desbrow B, Anderson S, Barrett J, Rao E, Hargreaves M. Carbohydrate-electrolyte feedings and 1 hour time trial cycling performance. Int J Sports Nutr Exerc Metab. 2004; 14: 541-549.

PubMed ID: 15673100
 
Study Design:
Randomized crossover trial
Class:
A - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:
To determine if a commercial sports drink consumed throughout a cycling time trial of approximately 60 minutes improves performance.
Inclusion Criteria:
Well-trained cyclists and triathletes.
Exclusion Criteria:
None specifically mentioned.
Description of Study Protocol:
  • Recruitment: Methods not specified
  • Design: Randomized crossover trial
  • Blinding used: Double-blind.

Intervention

  • Subjects were asked to complete a time trial following 24 hours of dietary and exercise control
  • Trials were separated by four days
  • Subjects were given food, 57.4±2.4kcal per kg and 9.1±0.4g carbohydrate per kg
  • During exercise, they were given 14ml per kg of either the 6% carbohydrate-electrolyte solution or carbohydrate-free placebo.

Statistical Analysis

Presence of any order effect and effect of drinks on performance were tested with paired T-tests.

Data Collection Summary:

Timing of Measurements

  • Measurements were made based on time trial
  • Blood samples were taken at end of trial.

Dependent Variables

  • Performance was measured by time trial
  • Blood samples were analyzed for glucose.

Independent Variables

During exercise, subjects were given 14ml per kg of either 6% carbohydrate-electrolyte solution or carbohydrate-free placebo.

Control Variables

Subjects were given all foods and fluids for 24 hours prior to testing.
Description of Actual Data Sample:
  • Initial N: Nine subjects, all male
  • Attrition (final N): Nine
  • Age: Mean age, 30.0±7.3 years
  • Ethnicity: Not mentioned
  • Location: Australia.
Summary of Results:

Trial Time (Minutes:Seconds) Power (Watts)

Carbohydrate-electrolyte

62:34±6:44 283.0±25.0

Placebo

62:40±5:35

282.9±29.3

Other Findings

  • Dietary intake was 4,316±370kcal, 57.4±2.4kcal per kg, 682±57g total carbohydrate, 9.1±0.4g carbohydrate per kg and 4,037±760ml total fluid
  • No test order effect was seen
  • Subjects' performance did not greatly improve while consuming the sports drink, based on time (62:34±6:44 minutes:seconds for carbohydrate-electrolyte and 62:40±5:35 minutes:seconds for placebo) or power output (283.0±25.0W for carbohydrate-electrolyte and 282.9±29.3W for placebo; both P>0.05).
Author Conclusion:
In conclusion, this study was designed to examine the effect of commercial sports drinks on performance when an athlete complies with the guidelines suggested for optimal pre-exercise nutrition (i.e., high-dietary carbohydrate intake and a carbohydrate meal two to four hours prior to exercise). Under such conditions, carbohydrate-electrolyte ingestion had no effect on one-hour cycling performance.
Funding Source:
Industry:
Nestle Australia
Food Company:
University/Hospital: Deakin University (Australia)
Reviewer Comments:
  • Inclusion and 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