EAL

NAP: Recovery (2007)

Citation:

Burke LM, Collier GR, Broad EM, Davis PG, Martin DT, Sanigorski AJ, Hargreaves M. Effect of alcohol intake on muscle glycogen storage after prolonged exercise. J Appl Physiol. 2003; 95 (3): 983-990.

PubMed ID: 12740311

Study Design:

Randomized controlled trial

Class:

A - Click here for explanation of classification scheme.

Quality Rating:

NEUTRAL: See Quality Criteria Checklist below.

Research Purpose:

To test the direct effect of alcohol added to a high-carbohydrate recovery diet, as well as its indirect effects in displacing carbohydrates from the post-exercise diet, on post-exercise muscle glycogen restoration.

Inclusion Criteria:

Well-trained cyclists, self-described as light drinkers (under 20g per day of alcohol).

Exclusion Criteria:

Past or current history of heavy alcohol intake (over 50g per day)
History of gastrointestinal pathology such as ulcers
Current use of any medications.

Description of Study Protocol:

Recruitment: Recruited from local pool of well trained cyclists
Design: Randomized controlled crossover trial
Blinding used: Not used.

Intervention

Subjects completed three trials in crossover order: Control diet, alcohol displacement diet and Alcohol + Carbohydrate Diet.

Statistical Analysis

Metabolic profiles were compared by repeated-measures ANOVA
Contrast analysis was used to compare individual time points, with Scheffe post-hoc testing used to locate specific differences. Areas under the curve were also compared using repeated-measures ANOVA, with individual diets being compared by use of multiple-comparison and least significant difference post-hoc tests.
Glycogen storage during recovery was calculated as the difference between post-exercise and post-recovery levels and the differences between storage and with each dietary treatment were compared by using a two-tailed T-test with a Bonferroni correction.

Data Collection Summary:

Timing of Measurements

In each study, subjects completed three trials one week apart: Two meals during an eight-hour recovery period or four meals during a 24-hour recovery period
Meals were consumed at zero, three, eight and 21 hours
Exercise bout to deplete muscle glycogen was riding for two hours at 75% VO_2max, followed by four 30-second sprints
Venous blood samples were drawn before the start of exercise, before each meal and 30, 60, 90 and 120 minutes after each meal.

Dependent Variables

Muscle samples were obtained from vastus lateralis
Venous blood samples were analyzed for plasma glucose, insulin, triglycerides
Blood alcohol level measured using radiative energy attenuation assay
Muscle glycogen content measured with enzymatic fluorometric technique.

Independent Variables

Eight- and 24-hour studies

Control diet: Meals providing seven grams per kg per 24-hour period divided into four meals or 3.5g per kg per eight-hour period of 1.75g per kg CHO of high-GI foods, ~77% CHO

Alcohol displacement diet: 1.5 g/kg alcohol (vodka) displacing CHO energy from Control Diet, divided into 6 meals, ~37% CHO in 24 hour study, ~15% CHO in 8 hour study, ~22% alcohol
Alcohol + Carbohydrate Diet: 1.75g per kg CHO and 1.5g per kg alcohol, total CHO intake at 4.4g per kg per 24-hour period or 1.1g per kg per meal, approximately 49% CHO, approximately 18% alcohol

Food and activity diaries were used before trials to ensure that there was no strenuous activity undertaken for the previous 36 hours and a standardized diet containing at least 300g per day of CHO was to be consumed during the 48 hours before each treatment.

Description of Actual Data Sample:

Initial N: 15 cyclists, gender not mentioned. Initially, 12 were recruited for the first 24 hour trial, but 3 withdrew due to side effects of vomiting of excessive alcohol consumption.
Attrition (final N): 15 cyclists, 6 in the 8 hour recovery, 9 in the 24 hour recovery
Mean Age

Eight-hour study: 28.4±1.7 years
24-hour study: 28.7±2.2 years.

Ethnicity: Not mentioned
Other relevant demographics: Not mentioned
Location: Australia.

Summary of Results:

	Post-Exercise	Post-Recovery	Net Storage (Post-Recovery minus Post-Exercise)
Eight-hour: Control	11.5±2.8	56.0±3.6	44.6±6
Eight-hour: Alcohol Displacement	15.8±6.9	40.2±2.8	24.4±7, P<0.05
Eight-hour: Alcohol + CHO	16.2±5.3	52.5±6.6	36.2±8
24-hour: Control	20.8±5.5	102.5±8.8	81.7±5
24-hour: Alcohol Displacement	19.9±4.2	88.2±5.8	68.4±5, P<0.05
24-hour: Alcohol + CHO	21.8±5.1	106.9±10.0	85.1±9

Other Findings

Alcohol intake reduced post-meal glycemia, especially in the Alcohol Displacement Diet and 24-hour study, even though insulin responses were maintained
Alcohol intake increased serum triglycerides, particularly in the 24-hour study and Alcohol + Carbohydrate Diet
Glycogen storage was decreased in the Alcohol Displacement Diet, compared with Control at eight hours (24.4±7 vs. 44.6±6mmol per kg wet weight, P<0.05) and 24 hours (68±5 vs. 82±5mmol per kg wet weight, P<0.05)
There was a trend to reduced glycogen storage with the Alcohol + Carbohydrate Diet in eight hours (36.2±8mmol per kg wet weight, P=0.1), but no difference in 24 hours (85±9mmol per kg wet weight).

Author Conclusion:

In summary, the intake of large amounts of alcohol immediately after prolonged exercise was associated with impairments of CHO and lipid metabolism
Evidence for a direct effect of elevated blood alcohol concentrations on muscle glycogen synthesis was unclear, but it appears that if an early impairment of glycogen synthesis exists, it may be compensated by adequate CHO intake and longer recovery time
The most important effects of alcohol intake on glycogen resynthesis are likely to be indirect, by interfering with the athlete's ability or interest to achieve the recommended amounts of CHO required for optimal glycogen restoration. Athletes therefore are guided to follow the guidelines for sensible use of alcohol in sport, in conjunction with the well-supported recommendations for recovery eating.

Funding Source:

Government:

West Australian Health Promotion Foundation

Reviewer Comments:

Equivalent of approximately 11 alcoholic drinks consumed in three hours
Exclusion of subjects who vomited resulted in subjects with higher tolerance and not necessarily all athletes.

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?		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?		???
	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?	???
	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?	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