EAL

NAP: Recovery (2007)

Citation:

Van Hall G, Shirreffs SM, Calbet JAL. Muscle glycogen resynthesis during recovery from cycle exercise: no effect of additional protein ingestion. J Appl Physiol. 2000; 88 (5): 1,631-1,636.

PubMed ID: 10797123

Study Design:

Randomized Crossover Trial

Class:

A - Click here for explanation of classification scheme.

Quality Rating:

NEUTRAL: See Quality Criteria Checklist below.

Research Purpose:

To investigate whether post-exercise carbohydrate intake, supplemented with protein, can enhance muscle glycogen resynthesis rate and leg glucose uptake when the latter is close to the maximal rate observed with only carbohydrate ingestion.

Inclusion Criteria:

Healthy, trained volunteers.

Exclusion Criteria:

None specifically mentioned.

Description of Study Protocol:

Recruitment: Methods not described
Design: Randomized crossover trial
Blinding used: Not used; lab tests.

Intervention

Each subject underwent three trials separated by one month
Subjects were studied during four hours of recovery from intense cycle exercise
Subjects immediately ingested 600ml bolus and, every 15 minutes, a 150-ml bolus of either 1.67g/kg/L sucrose and 0.5g/kg/L whey protein hydrolysate, 1.67g/kg/L sucrose only or water.

Statistical Analysis

Statistical analysis was done using the non-parametric Wilcoxon signed-rank test to determine differences between data obtained in the three different trials.

Data Collection Summary:

Timing of Measurements

Muscle biopsies were taken just before the first bolus of drink, then at 1.5 and four hours after recovery
Blood samples were taken before first bolus, every 10 minutes during the first hour and then every 30 minutes afterwards.

Dependent Variables

Muscle biopsies were taken from vastus lateralis
Blood samples were analyzed for plasma glucose, insulin and glucagon.

Independent Variables

Ingestion of 600-ml bolus immediately after exercise and, every 15 minutes, a 150-ml bolus of either 1.67g/kg/L sucrose and 0.5g/kg/L whey protein hydrolysate, 1.67g/kg/L sucrose only or water.

Description of Actual Data Sample:

Initial N: Five healthy trained volunteers, gender not specified
Attrition (final N): Five
Age: Mean, 26±2 years
Ethnicity: Not mentioned
Location: Denmark.

Summary of Results:

Other Findings

Glycogen depletion was the same for all three trials
CHO+protein and CHO-only ingestion caused an increase in arterial glucose concentration, compared with water ingestion during four hours of recovery (8.7±0.3mmol and 9.6±0.2mmol per L, respectively, decreasing to approximately 6.3mmol per L for both drinks, compared to 5.2mmol per L for water)
With CHO-only ingestion, glucose concentration was 1.0mmol to 1.5mmol per L higher during the first hour of recovery, compared with CHO+protein
Leg glucose uptake was initially 0.7mmol per minute with water ingestion and decreased gradually with no measurable glucose uptake observed at three hours of recovery
Leg glucose uptake was rather constant at 0.9mmol per minute with CHO+protein and CHO ingestion and insulin levels were stable at 70mU, 45mU and five mU per L for CHO+protein, CHO and water, respectively. Insulin levels were higher for CHO+protein.
Glycogen resynthesis rates were 52±7mmol, 48±5mmol and 18±6mmol for the first 1.5 hours of recovery and decreased to 30±6mmol, 36±3mmol and 8±6mmol per kg dry muscle per hour between 1.5 and four hours for CHO+protein, CHO and water, respectively
No differences could be observed between CHO+protein and CHO-only in leg glucose uptake or glycogen resynthesis rate.

Author Conclusion:

In conclusion, coingestion of carbohydrate and protein, compared with ingestion of carbohydrate alone, did not increase leg glucose uptake or the glycogen resynthesis rate after intense cycle exercise
It seems that protein ingestion per se or via stimulation of insulin secretion cannot increase muscle glycogen resynthesis rate in humans, when an optimal carbohydrate supplementation regime is followed during recovery from exercise.

Funding Source:

Industry:

MD Foods

Food Company:

Not-for-profit

Foundation associated with industry:

Reviewer Comments:

Inclusion criteria, exclusion criteria and recruitment methods were not well-defined
Subjects were not well-described
No power calculations were done; small sample size.

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?	No
	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?	No
	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?	No
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