EAL

NAP: Training (2007)

Citation:

Fairchild TJ, Fletcher S, Steele P, Goodman C, Dawson B, Fournier PA. Rapid carbohydrate loading after a short bout of near maximal-intensity exercise. Med Sci Sports Exerc. 2002; 34 (6): 980-986.

PubMed ID: 12048325

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 whether one day of a high-carbohydrate intake after a short bout of high-intensity exercise can lead to the attainment of supranormal levels of muscle glycogen.

Inclusion Criteria:

Healthy endurance-trained male subjects.

Exclusion Criteria:

None specifically mentioned.

Description of Study Protocol:

Recruitment: Subjects were selected; methods not described
Design: Subjects cycled for 150 seconds at 130% VO_2peak followed by 30 seconds of all-out cycling. During the following 24 hours, each subject was asked to ingest high-carbohydrate foods with a high-glycemic index.
Blinding used: Not used; lab tests.
Intervention: Subjects consumed 12g CHO per kg lean body mass (equal to 10.3g per kg body mass) of high-CHO foods with a high glycemic index.

Statistical Analysis

Differences in muscle glycogen levels were analyzed using one-way ANOVA with repeated measures followed by a Tukey's post-hoc comparison
Correlations between both muscle glycogen determinations were calculated using Pearson correlation coefficients.

Data Collection Summary:

Timing of Measurements

Subjects were weighed, food records obtained and muscle biopsies taken before any food was consumed on testing day
Second biopsies were taken at 24 hours after consumption of CHO-loading diet.

Dependent Variables

Muscle biopsies were taken from vastus lateralis muscle and analyzed for muscle glycogen
Lean body mass was determined through underwater hydrostatic weighing
Gas collection was measured with Morgan Ventilation Monitor.

Independent Variables

Ingestion of high-CHO, high-glycemic index foods for 24 hours
Participants provided with electronic scale and measuring cups to ensure accurate recording of food intake for four days prior to CHO-loading and during day of CHO-loading.

Description of Actual Data Sample:

Initial N: Seven subjects, all male
Attrition (final N): Seven
Age: Mean, 22.4±3.2 years
Ethnicity: Not mentioned.
Location: Australia.

Summary of Results:

	Normal Diet	Loading Diet
CHO intake (grams per kg LBM)	6.6±1.0	12.2±0.6
Energy intake (MJ per day)	12.85±3.15	16.84±1.66

Other Findings

Muscle glycogen increased from pre-loading levels of 109.1±8.2 to 198.2±13.1mmol per kg wet weight within only 24 hours, corresponding to an increase of 82%. These levels being comparable to or higher than those reported by others over a two- to six-day regimen.
Densitometric analysis of muscle sections stained with periodic acid-Schiff not only corroborated these findings but also indicated that after 24 hours of high-CHO intake, glycogen stores reached similar levels in Type I, IIa and IIb muscle fibers.

Author Conclusion:

This study shows for the first time that it is possible to accumulate supranormal muscle glycogen levels within only 24 hours by feeding athletes with 12g CHO per kg lean body mass (10.3g CHO per kg body mass) after a three-minute bout of high-intensity exercise

The CHO-loading regimen represents a marked improvement over all those proposed to date in that:

Only one instead of three days is required to increase muscle glycogen stores to supramaximal levels
Normal training regimens can be maintained up until the day before competition with minimum disruption to training and pre-event preparation.

Funding Source:

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

Reviewer Comments:

Subject selection may have led to bias.

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?		No
	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?		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?		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?		No
	9.1.	Is there a discussion of findings?	Yes
	9.2.	Are biases and study limitations identified and discussed?	No
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