EAL

NAP: Recovery (2007)

Citation:

Tarnopolsky MA, Bosman M, MacDonald JR, Vandeputte D, Martin J, Roy BD. Postexercise protein-carbohydrate and carbohydrate supplements increase muscle glycogen in men and women. J Appl Physiol. 1997 Dec; 83 (6): 1,877-1,883.

PubMed ID: 9390958

Study Design:

Non-Randomized Crossover Trial

Class:

C - Click here for explanation of classification scheme.

Quality Rating:

POSITIVE: See Quality Criteria Checklist below.

Research Purpose:

To compare the rate of glycogen resynthesis after endurance exercise when the energy content of both the post-exercise supplement and the 24-hour energy intake of all trials was held constant and to examine post-exercise glycogen repletion in both sexes.

Inclusion Criteria:

Trained endurance athletes
Men with peak O₂ consumption of at least 55ml per kg per minute
Women with peak O₂ consumption of at least 50ml per kg per minute
Women in mid-follicular phase.

Exclusion Criteria:

None specifically mentioned.

Description of Study Protocol:

Recruitment: Methods not specified
Design: Non-randomized crossover trial; all subjects received supplements in same order
Blinding used: Double-blind.

Intervention

Each subject completed three sequential trials separated by three weeks
After endurance exercise (90 minutes at 65% peak O₂consumption), supplements were provided immediately and one hour post-exercise: Either CHO (0.75g per kg) + protein (0.1g per kg) + fat (0.02g per kg), CHO only (1.0g per kg) or placebo of artificial sweetener.

Statistical Analysis

Muscle and blood data analyzed by using repeated-measures ANOVA (gender x time x condition)
When a significant interaction was found, Tukey's post-hoc analysis was used to locate the pairwise differences
Integrated area under the curve data for glucose and insulin was analyzed by one-way repeated-measures ANOVA.

Data Collection Summary:

Timing of Measurements

Blood samples collected every 30 minutes during exercise and every 20 minutes up to two hours post-exercise, with additional samples collected at three and four hours post-exercise
Muscle biopsies taken immediately after exercise and four hours after supplement.

Dependent Variables

Blood samples analyzed for glucose and insulin
Muscle biopsies obtained from vastus lateralis
Urine samples for analysis of creatinine and total urea nitrogen.

Independent Variables

Supplements were provided immediately and one hour post-exercise: Either CHO (0.75g per kg) + protein (0.1g per kg) + fat (0.02g per kg), CHO only (1.0g per kg) or placebo of artificial sweetener
Subjects were given pre-packaged, isoenergetic, isonitrogenous diets, individualized to their habitual diet, for the day before and during the trials
Compliance checked by analyzing diet checklists returned by each subject.

Description of Actual Data Sample:

Initial N: 16 subjects, 8 men, 8 women
Attrition (final N): 16
Mean age: Men, 22.1±2.2 years; women, 20.3±0.89 years
Ethnicity: Not mentioned
Other relevant demographics: Women tested in mid-follicular phase
Anthropometrics: Men and women matched for training history. Men and women were significantly different in terms of weight, lean body mass, body fat percentage and peak VO₂, as can be explained by gender differences.
Location: Canada.

Summary of Results:

	CHO-Protein-Fat	CHO Only	Placebo
RER: Men	0.934±0.03	0.902±0.03	0.918±0.02
RER: Women	0.902±0.03, P<0.005	0.882±0.04, P<0.005	0.896±0.03, P<0.005

Other Findings

There were no significant gender or time differences in VO₂, heart rate, 24-hour urea nitrogen or creatinine in any of the trials
During exercise, women oxidized more lipid than did men (P<0.05)
Both of the supplement trials resulted in greater post-exercise glucose and insulin, compared with placebo (P<0.01), with no gender differences
Similarly, both of these trials resulted in increased glycogen resynthesis (37.2 for CHO vs. 24.6mmol per kg dry muscle per hour for CHO-protein-fat), compared with placebo (7.5mmol per kg dry muscle per hour, P<0.001), with no gender differences.

Author Conclusion:

In summary, we have demonstrated that, compared with a placebo drink, CHO and CHO-protein-fat supplements, when given early after endurance exercise, result in more rapid glycogen resynthesis rates
Importantly, this finding is true for both male and female athletes.

Funding Source:

Industry:

Mead-Johnson (Canada)

Food Company:

University/Hospital:

McMaster University

Reviewer Comments:

Randomized trial became non-randomized due to researcher error
Larger sample size than is typically seen in these studies
Pre-packaged diets provided to subjects.

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?		Yes
	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?		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