EAL

NAP: Training (2007)

Citation:

Bussau VA, Fairchild TJ, Rao A, Steele P, Fournier PA. Carbohydrate loading in human muscle: an improved 1 day protocol. Eur J Appl Physiol. 2002; 87: 290-295.

PubMed ID: 12111292

Study Design:

Non-Randomized Controlled Trial

Class:

C - Click here for explanation of classification scheme.

Quality Rating:

NEUTRAL: See Quality Criteria Checklist below.

Research Purpose:

To determine if, in less than three days, a high-carbohydrate intake combined with physical inactivity can lead to the attainment of maximal levels of muscle glycogen content in trained athletes and whether carbohydrate-loading occurs in types I, IIa and IIb muscle fibres.

Inclusion Criteria:

Endurance-trained cyclists or triathletes aged 18-30 years.

Exclusion Criteria:

None specifically mentioned.

Description of Study Protocol:

Recruitment: Subjects were selected for study
Design: Non-randomized clinical trial
Blinding used: Not applicable; lab tests
Intervention: Subjects consumed a high-CHO diet, while remaining physically inactive for three days.

Statistical Analysis

Differences in muscle glycogen contents, using either histochemical or biochemical methods, were analyzed using a one-way ANOVA with repeated measurements, followed by a Tukey's post-hoc comparison
Correlations between weighted average of PAS-stain intensity across all three muscle fiber types were calculated using the Pearson correlation coefficient.

Data Collection Summary:

Timing of Measurements

Subjects attended a fitness-testing and familiarization session
Muscle biopsies were taken prior to carbohydrate-loading and after one and three days of the high-CHO diet.

Dependent Variables

Body weight
Muscle glycogen from muscle biopsies taken from vastus lateralis muscle
VO_2peak determined.

Independent Variables

Subjects asked to eat 10g per kg per day of high-CHO foods having high-glycemic index for three days
Subjects asked to remain physically inactive
Subjects given electronic scales and measuring cups to ensure accurate dietary recording for four-day dietary analysis prior to CHO-loading.

Description of Actual Data Sample:

Initial N: Eight male athletes
Attrition (final N): Eight subjects
Age: Mean, 23.3±4.0 years
Ethnicity: Not mentioned
Other relevant demographics: Mean VO_2peak 59.3±6.2ml per kg per minute
Location: Australia.

Summary of Results:

Normal Diet (MJ/day)	17.03±2.81
Loading Diet (MJ/day)	19.22±3.60
CHO Intake; Normal	5.8±0.3g per kg per day
CHO Intake; Loading	10.2±1.1g per kg per day

Other Findings

Muscle glycogen content increased significantly (P<0.05) from pre-loading levels of 95±5 to 180±15mmol per kg wet mass after only one day and remained stable afterwards, despite another two days of carbohydrate-rich diet
Densitometric analyses of muscle sections stained with periodic acid-Schiff not only supported these findings, but also indicated that only one day of high-carbohydrate intake was required for glycogen stores to reach maximal levels in types I, IIa and IIb muscle fibres.

Author Conclusion:

In conclusion, the carbohydrate-loading regimen described in this study represents a marked improvement over those proposed to date in that:

Even without a glycogen-depleting period of exercise, trained athletes can achieve maximal levels of glycogen content in all muscle fibers within 24 hours, with no added benefit if the high-carbohydrate intake is extended for more days
A normal training regimen can be maintained up until the day prior to competition with minimal disruption to training and pre-event preparation.

Funding Source:

Government:	Australian Research Council
University/Hospital:	University of Western Australia

Reviewer Comments:

Subjects were selected rather than recruited
Inclusion criteria and exclusion criteria were not well-defined
Authors note that subjects were already eating high-carbohydrate diets having high glycemic indices prior to the 24-hour carbohydrate-loading
Did not study athletic performance.

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?		N/A
	3.1.	Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT)	N/A
	3.2.	Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?	N/A
	3.3.	Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.)	N/A
	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?	N/A
	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?		???
	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?	???
	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?	N/A
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)?	Yes
	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