NAP: Recovery (2007)

Citation:

Carrithers JA, Williamson DL, Gallagher PM, Godard MP, Schulze KE, Trappe SW. Effects of postexercise carbohydrate-protein feedings on muscle glycogen restoration. J Appl Physiol. 2000 Jun; 88 (6): 1976-1982.

PubMed ID: 10846008
 
Study Design:
Randomized crossover trial
Class:
A - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:
To determine the effects of post-exercise eucaloric CHO-protein feedings on muscle glycogen restoration after an exhaustive cycle ergometer exercise bout.
Inclusion Criteria:
  • Collegiate cyclists
  • Non-smokers
  • Glucose-tolerant, having fasted serum glucose concentration of less than 115mg per dL, peak value of less than 200mg per dL and two-hour concentration of less than 140mg per dL.
Exclusion Criteria:
  • Metabolic or cardiovascular disorders
Description of Study Protocol:
  • Recruitment: Recruitment methods not specified
  • Design: Randomized crossover trial
  • Blinding used: Not used; lab tests.

Intervention

Subjects performed three trials of a four-day muscle glycogen depletion protocol, each separated by one week: 100% alpha-D-glucose, 70% CHO/20% protein/10% fat or 86% CHO/14% amino acid. All feedings were eucaloric, based on 1.0g CHO per kg body weight per hour and were administered every 30 minutes during a four-hour muscle glycogen restoration period.

Statistical Analysis

  • Comparisons of means between trials was conducted using two-way repeated measures ANOVA (treatment x time)
  • When significance occurred between means, Tukey's post-hoc test was used to determine where significance occurred.
Data Collection Summary:

Timing of Measurements

  • Muscle biopsies were obtained immediately and four hours after exercise
  • Blood samples were drawn immediately and every half hour for four hours during recovery.

Dependent Variables

  • Muscle biopsies were obtained from vastus lateralis
  • Blood samples were analyzed for glucose and insulin.

Independent Variables

100% alpha-D-glucose, 70% CHO/20% protein/10% fat or 86% CHO/14% amino acid.
Description of Actual Data Sample:
  • Initial N: Eight males recruited, seven males met inclusion criteria
  • Attrition (final N): Seven
  • Age: Mean, 25.6±1.3 years
  • Ethnicity: Not mentioned
  • Location: Indiana.
Summary of Results:

Other Findings

  • There were no differences in dietary intake during the three days prior to the trial
  • There were no differences in muscle glycogen depletion between trials
  • Increases in muscle glycogen concentrations for the three feedings were 118mmol per kg dry weight, however no differences among the feedings were apparent
  • The serum glucose and insulin responses did not differ throughout the restoration period among the three feedings.
Author Conclusion:
  • In summary, muscle glycogen concentrations for the three trials were similar immediately post-exercise and again four hours after the cessation of exercise
  • In addition, the serum insulin and glucose responses among the three eucaloric feedings displayed no differences at any time throughout the four-hour restoration period. Therefore, it appears that the addition of protein or amino acids to an eucaloric post-exercise CHO feeding does not enhance the restoration of muscle glycogen, compared with a CHO-only feeding.
  • Thus, provided the caloric content is similar and adequate amounts of CHO are consumed (more than 0.70g per kg body weight per hour) after exhaustive exercise, the addition of protein or amino acids to a CHO feeding does not appear to enhance muscle glycogen restoration.
Funding Source:
Industry:
General Nutrition
Food Company:
University/Hospital: Ball State University
Reviewer Comments:
  • Four-day muscle glycogen depletion protocol
  • All feedings were eucaloric
  • No power calculations were done.
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? 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? 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? ???
  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? 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