EAL

NAP: Competition (2007)

Citation:

Nicholas CW, Williams C, Lakomy HKA, Phillips G, Nowitz A. Influence of ingesting a carbohydrate-electrolyte solution on endurance capacity during intermittent, high-intensity shuttle running. J Sports Sci. 1995; 13 (4): 283-290.

PubMed ID: 7474041

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 examine the influence of ingesting a commonly available sports drink (6.9% carbohydrate-electrolyte solution) on sprint performance and running capacity during a prolonged intermittent high-intensity shuttle running test.

Inclusion Criteria:

Trained, healthy male games players.

Exclusion Criteria:

None specifically mentioned.

Description of Study Protocol:

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

Intervention

Subjects performed two exercise trials seven days apart. On each occasion, they completed 75 minutes of exercise, comprised of five 15-minute periods of intermittent running, consisting of sprinting interspersed with periods of jogging and walking, followed by intermittent running to fatigue.
Subjects were randomly allocated either a 6.9% carbohydrate-electrolyte solution or a non-carbohydrate placebo immediately prior to exercise (five ml per kg of body mass) and every 15 minutes thereafter (two ml per kg of body mass).

Statistical Analysis

Performance times of the two groups were compared using Student's T-test for correlated data
Physiological and blood biochemical responses in both trials were analyzed using a two-way (treatment x time) ANOVA for repeated measures
Significant differences between means were identified using the Scheffe post-hoc test.

Data Collection Summary:

Timing of Measurements

Blood samples were obtained at rest, after 15, 30, 45, 60 and 75 minutes during running, at exhaustion and at 15, 30 and 45 minutes after each prolonged intermittent high-intensity shuttle running test
Heart rate was recorded every 15 minutes
RPE and gut fullness were obtained at 15-minute intervals and at fatigue.

Dependent Variables

Blood samples were analyzed for glucose, lactate, plasma FFA, glycerol, ammonia and serum insulin, hematocrit, hemoglobin and electrolyte concentrations
Running and walking speeds and sprint times
Heart rate was recorded through telemetry
Subjective ratings of perceived exertion and gut fullness.

Independent Variables

6.9% carbohydrate-electrolyte solution or a non-carbohydrate placebo immediately prior to exercise (five ml per kg of body mass) and every 15 minutes thereafter (two ml per kg of body mass).

Control Variables

During two days preceding the trials, subjects refrained from any strenuous physical activity and consumed their normal diet.

Description of Actual Data Sample:

Initial N: Nine males
Attrition (final N): Nine
Age: Mean, 24.8±0.6 years
Ethnicity: Not mentioned
Location: United Kingdom.

Summary of Results:

Other Findings

During the intermittent running to fatigue, the subjects were able to continue running longer when fed carbohydrates (CHO=8.9±1.5 minutes vs. control=6.7±1.0 minutes, 2.2 minutes longer; P<0.05)
The distance covered in both trials was 10.8±0.2km for the first part of the test, but during the intermittent running to fatigue, the distance covered was 1.7±0.3 for CHO and 1.3±0.2km for control (P<0.05)
Differences in blood glucose concentration between trials occurred at 30 minutes during exercise, at exhaustion (P<0.05) and at 15, 30 (P<0.01) and 45 minutes (P<0.05) post-exercise
Serum insulin values tended to be higher at each sampling point, but only reached statistical significance between trials in the post-exercise period at 15 and 30 minutes (P<0.05)
There were no differences in plasma FFA concentration between trials during exercise, however these values were higher in the control trial than in the CHO trial at 30 minutes (P<0.05) and 45 minutes (P<0.01) post-exercise
Plasma ammonia increased in both groups over the duration of exercise (P<0.01)
There were no differences in serum sodium and potassium concentrations between trials
There were no differences in either blood lactate concentrations or heart rate response between trials.

Author Conclusion:

In summary, the ingestion of a 6.9% carbohydrate-electrolyte solution, which provided 47g of carbohydrates per hour during 75 minutes of high-intensity intermittent running, improved endurance running capacity by 33%, compared with drinking a placebo.

Funding Source:

University/Hospital:

Loughborough University (UK)

Reviewer Comments:

Inclusion criteria, exclusion criteria and recruitment methods were not well-defined.

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?		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