EAL

NAP: Competition (2007)

Citation:

Ball TC, Headley SA, Vanderburgh PM, Smith JC. Periodic carbohydrate replacement during 50 minutes of high-intensity cycling improves subsequent sprint performance. Int J Sport Nutr. 1995; 5: 151-158.

PubMed ID: 7670454

Study Design:

Non-randomized crossover trial

Class:

C - Click here for explanation of classification scheme.

Quality Rating:

NEUTRAL: See Quality Criteria Checklist below.

Research Purpose:

To investigate the effect of a 7% carbohydrate-electrolyte drink on sprint capacity immediately following 50 minutes of high-intensity cycling.

Inclusion Criteria:

Trained male cyclists.

Exclusion Criteria:

Subjects completed a medical history questionnaire prior to testing: None had any medical history that would exclude them from participation.

Description of Study Protocol:

Recruitment

Methods not specified.

Design

Non-randomized crossover trial: Trials were counterbalanced but not random.

Blinding Used

Single-blind lab tests.

Intervention

Tests performed one week apart
After a 12-hour overnight fast, subjects performed two 50-minute simulated time trials on a Monark stationary cycle ergometer
Subjects consumed either the carbohydrate-electrolyte or flavored water placebo at 10, 20, 30 and 40 minutes during the time trial
At the conclusion of each 50-minute time trial, subjects immediately performed a Wingate Anaerobic Power Test.

Statistical Analysis

Peak power, mean power, minimum power and rate of fatigue in the Wingate Anaerobic Power Test were compared between treatments using paired T-tests
For 50-minute trials, heart rate and RPE were analyzed using MANOVA with repeated measures across times and trials
Collapsed time intervals were used because of small sample sizes (zero to 15 minutes, 15 to 35 minutes, 35 to 50 minutes).

Data Collection Summary:

Timing of Measurements

All measurements completed during exercise tests.

Dependent Variables

Peak power, mean power and fatigue index were measured through cycling tests and Wingate Anaerobic Power Test
Gas exchange measurements and RER were measured with metabolic cart
RPE
Heart rate.

Independent Variables

Subjects consumed either the carbohydrate-electrolyte or flavored water placebo at 10, 20, 30 and 40 minutes during the time trial
Subjects asked to maintain similar dietary intake and same training regimen prior to trials.

Description of Actual Data Sample:

Initial N: Eight male cyclists
Attrition (final N): Eight
Age: Mean age 26.9±4.4 years
Ethnicity: Not mentioned
Location: Massachusetts.

Summary of Results:

	Placebo	Carbohydrate-Electrolyte	P-Value
RPE	5.6±1.01	4.99±1.11	0.003
Heart rate (beats per minute)	161.9±6.80	160.1±10.00	NS
Mean power (W)	655.3±74.1	700.6±84.9	0.009
Peak power (W)	747.6±97.3	794.0±83.5	0.020
Minimum power (W)	584.5±93.2	627.0±101.3	0.020
Fatigue rate (percentage)	21.3±12.4	20.9±10.4	NS

Other Findings

Neither mean training volumes nor carbohydrate intakes were different between trials
Peak power, mean power and minimum power were significantly higher for the carbohydrate-electrolyte trials (P<0.05), whereas mean RPE was lower
Mean heart rate and fatigue index were not different between trials.

Author Conclusion:

In conclusion, cyclists and perhaps other endurance athletes may benefit from periodically ingesting a carbohydrate-electrolyte beverage during moderate duration, high-intensity competition after an overnight fast. This benefit may be in decreased RPE during the trial as well as improved sprint performance at the trial's conclusion. In cycling, where race success is largely determined by sprint capacity at the race's finish, these findings have particular relevance.
Further research is needed to better understand the limiting factors of performance, such as sprint capacity, after moderate duration, high-intensity exercise.

Funding Source:

University/Hospital:

Springfield College

Reviewer Comments:

Recruitment methods not well defined
Time intervals are not equal in length and seem arbitrary
Muscle glycogen and blood samples not analyzed
Subjects were fasting.

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?	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?	???
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?	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?	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?	???
	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