NAP: Recovery (2007)

Citation:

Ivy JL, Goforth Jr. HW, Damon BM, McCauley TR, Parsons EC, Price TB. Early postexercise muscle glycogen recovery is enhanced with a carbohydrate-protein supplement. J Appl Physiol. 2002 Oct; 93 (4): 1,337-1,344.

PubMed ID: 12235033
 
Study Design:
Non-randomized crossover trial
Class:
C - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:
To test the hypothesis that a CHO-protein supplement would be more effective in the replenishment of muscle glycogen after exercise, compared with a CHO supplement of equal CHO content or caloric equivalency.
Inclusion Criteria:
  • Trained male cyclists
  • Screened by interview for medical history.
Exclusion Criteria:
  • Had no family history of diabetes, hypertension or metabolic disorder.
Description of Study Protocol:
  • Recruitment: Methods not specified
  • Design: Non-randomized crossover trial, subjects were rank ordered according to VO2max and assigned treatments according to pre-determined counter-balanced design
  • Blinding used: Not used; lab tests.

Intervention

  • Subjects participated in the study on three separate occasions, separated by one month
  • After 2.5±0.1 hours of intense cycling to deplete muscle glycogen stores, subjects received CHO-protein (80g CHO, 28g protein, six grams fat), low-CHO (80g CHO, six grams fat) or high-CHO (108g CHO, six grams fat) supplement immediately after exercise (10 minutes) and two hours post-exercise.

Statistical Analysis

  • Two-way ANOVA (treatment x time) with repeated measures was employed to identify significant major effects
  • Significant differences among means were determined by pairwise comparisons, using estimated marginal means.
Data Collection Summary:

Timing of Measurements

Before exercise and during four hours of recovery, muscle glycogen of the vastus lateralis was determined at 20, 40, 60, 120, 180 and 240 minutes and blood samples were collected at 30, 60, 120, 150, 180, 210 and 240 minutes.

Dependent Variables

  • Muscle glycogen was determined through nuclear magnetic resonance spectroscopy
  • Blood samples were analyzed for glucose, lactate, insulin, catecholamines and FFA.

Independent Variables

  • CHO-protein (80g CHO, 28g protein, six grams fat), low-CHO (80g CHO, six grams fat) or high-CHO (108g CHO, six grams fat) supplement immediately after exercise (10 minutes) and two hours post-exercise
  • Subjects were monitored in GCRC.
Description of Actual Data Sample:
  • Initial N: Seven subjects, all male
  • Attrition (final N): Seven
  • Age: Mean, 23±1 years
  • Ethnicity: Not mentioned
  • Location: Connecticut.
Summary of Results:

Other Findings

  • Exercise significantly reduced the muscle glycogen stores (final concentrations: 40.9±5.9mmol per L CHO-protein; 41.9±5.7mmol per L, high-CHO; 40.7±5.0mmol per L, low-CHO). There were no differences among trials before or after exercise.
  • After 240 minutes of recovery, muscle glycogen was significantly greater for the CHO-protein treatment (88.8±4.4mmol per L, 46.8% replenished), when compared with the low-CHO (70.0±4.0mmol per L, 28.0% replenished; P=0.004) and high-CHO (75.5±2.8mmol per L, 31.1% replenished; P=0.013) treatments
  • Glycogen storage did not differ significantly between the low-CHO and high-CHO treatments
  • There were no significant differences in the plasma insulin responses among treatments, although plasma glucose was significantly lower during the CHO-protein treatment 
  • No differences in plasma FFA, epinephrine or norepinephrine were observed between trials during exercise and recovery.
Author Conclusion:
  • In conclusion, the present results suggest that a distinct advantage in muscle glycogen storage can be achieved after exercise with the addition of protein to a carbohydrate supplement
  • When supplementation occurs immediately post-exercise and two hours post-exercise, this advantage appears to be maintained even when compared with a high-CHO supplement
  • The increased rate of muscle glycogen storage after CHO-protein supplementation does not appear to be due to an enhanced plasma insulin response and is most evident during the first 40 minutes of recovery. This later finding would suggest that a CHO-protein supplement might be most beneficial during short recovery periods.
  • CHO-protein supplementation for exercise recovery might also be advantageous if minimizing carbohydrate consumption is necessary or a personal preference, such as during a weight management program.
Funding Source:
Reviewer Comments:
Subjects monitored in GCRC.
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? N/A
  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