NAP: Recovery (2014)


Sousa M, Simoes HG, Campi de Castro C, Garcia Otaduy MC, Negrao CE, Rodrigues Pereira RM, Madsen K, and Rossi da Silva ME. Carbohydrate supplementation increases intramyocellular lipid stores in elite runners. Metabolism Clinical Experimental, 2012: 61: 1,189-1,196.

Study Design:
Randomized Controlled Trial
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Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:

To determine the effects of carbohydrate (CHO) supplementation on exercise-induced hormone responses and post-training intramyocellular lipid stores (IMCL).

Inclusion Criteria:
  • Study participants were competitive male endurance runners who regularly participate in state, national and international competitions
  • Participants also signed an informed consent form. 
Exclusion Criteria:
  • Participants were excluded if they were not male and were not competitive endurance runners
  • Additional exclusion criteria were not stated by authors.
Description of Study Protocol:


Recruitment of participants was not described by the authors. 


Randomized, placebo-controlled trial using matched groups [for body weight, age, maximal oxygen consumption (VO2max)] conducted over period of eight days of intensive training. On Day Nine, participants did a post-training program. Magnetic resonance spectroscopy (H-MRS) and dual-energy X-ray absorptiometry (DXA) measurements were done on Day 10.

Blinding Used

The study was double-blinded. 


In the morning during intensive training, participants received either a carbohydrate supplement (one gram maltodextrin per kg body weight per hour of exercise) or a placebo solution supplement on Days One through Eight. For the CHO Group, this corresponded to daily CHO concentration of 61%. For the Control Group this corresponded to daily CHO concentration of 54%.

During the post-training program on day nine both groups received the following supplements:

  • Four ml per kg body weight 30 minutes before the first 1,000-m run and immediately after the first 1,000-m run and the intermittent running series. For the CHO Group, this was a 7% maltodextrin solution.
  • Two ml per kg body weight after the first 800-m run and then after each two series of 800-m runs. For the CHO Group, this was a 7% maltodextrin solution.
  • Three ml per kg body weight immediately after the second 1,000-m run and at 60 minutes of recovery. For the CHO Group, this was 1.2g per kg body weight maltodextrin.

Statistical Analysis

  • Two-way ANOVA was used to determine differences in blood variables between the two groups (treatment by time). Post-hoc Tukey test was used if differences were significant.
  • DXA and IMCL results were reported as delta percentage and were compared by T-test for un-paired samples. 
Data Collection Summary:

Timing of Measurements

  • Pre-trial testing nine days before the intensive training program included the first blood sample, use of H-MRS to determine IMCL stores, use of DXA to determine body composition, measurement of maximal oxygen consumption and a three-km performance test on a running track to calculate the mean velocity and the velocity at which they should exercise during the intermittent sessions and incremental running test on a treadmill until exhaustion to determine VO2max
  • On Day Nine, participants did a post-training program
  • Blood samples for determining free fatty acids, insulin, growth hormone and plasma epinephrine were collected at 140 minutes and 30 minutes before the intermittent running series and immediately after, after the second 1,000-m run and at 15 and 80 minutes of recovery
  • Blood samples for determining serum adiponectin were collected at pre-trial testing,140 minutes and 30 minutes before the intermittent running series and immediately after, and at 80 minutes of recovery
  • Before and after the intense training program IMCL concentration was measured in the morning after breakfast in the tibialis anterior (TA) of the soleus (SO) muscles of the right leg while in the supine position by H-MRS. Body composition of the subjects was determined pre- and post-training program after breakfast using DXA
  • Both second H-MRS and DXA measurement were done on Day 10. 

Dependent Variables

  • IMCL concentrations, measured using H-MRS in the SO and TA muscles
  • Free fatty acids, insulin, growth hormone, plasma epinephrine and serum adiponectin, measured by lab assessment.

Independent Variables

  • CHO-containing supplement
  • Placebo supplement.

Control Variables

Food diaries were kept by all participants for all foods eaten before and after the intensive training program. 
Description of Actual Data Sample:
  • Initial N: 24 males
  • Attrition (final N): None reported
  • Age: 28.0±1.2 years (29.1±1.6 years for the CHO Group, 26.9±1.9 for the Control Group)
  • Ethnicity: Not specified
  • Other relevant demographics: The participants had been training for the last 8.6±1.1 years.


  • The groups were fairly matched on height, weight, maximum heart rate and maximal oxygen consumption
  • Height for the CHO Group was 169.5±2.0cm and 170.2±2.5cm for the Control Group
  • Weight for the CHO Group was 60.2k±1.4kg and 62.3±1.6kg for the Control Group
  • Maximum heart rate in beats per minute for the CHO Group was 175.9±1.4 and 177.5±2.4 for the Control Group
  • VO2max for the CHO Group was 69.8±2.2ml/kg/minute and 68.5±1.9ml/kg/minute for the Control Group.


Summary of Results:

Key Findings

  • Free fatty acids were lower in the CHO Group after the second 1,000-m test (0.2±0.0mEq vs. 0.5±0.1mEq per L; P=0.009), 15 minutes of recovery (0.2±0.0mEq vs. 0.6±0.1mEq per L; P<0.001) and at 80 minutes of recovery (0.1±0.0mEq vs. 1.5±0.1mEq per L; P<0.001)
  • Insulin concentrations were higher in the CHO Group post-intermittent run (23.4±4.4mcU per ml vs. 12.8±1.2mcU per ml; P=0.022) and after 15 minutes (33.0±6.1mcU per ml vs. 7.7±0.8mcU per ml; P<0.001) and 80 minutes of recovery (41.9±7.8mcU per ml vs. 7.2±0.6mcU per ml; P<0.001)
  • Post-exercise, in the CHO Group epinephrine did not increase as much as in the Control Group and was not as statistically significant (P<0.05 vs. P<0.01)
  • Growth hormone increased less in the CHO Group than the Control Group after the intermittent run and after the second 1,000-m run, GH remained high but the difference was less significant in the CHO Group [348.0±144.6pg per ml (P<0.05) vs. 360.2±85.2pg per ml (P<0.001)]
  • No variations in adiponectin concentrations were observed in either group throughout the running protocol
  • Decline in performance in the second 1,000-m run was significantly lower in the CHO Group (5.3±1.0%) than in the Control Group (10.7±1.3%; P=0.0035)
  • There were no significant differences between groups in the 10-km continuous run at 85% mean three-km velocity (Vm3km), in heart rate or in rating of perceived exertion
  • The percentage change in TA-IMCL was higher in the CHO Group than in the Control Group (68.6±29.9 IMCL/H2O and 47.9±24.5 IMCL/Cr vs. -4.4±14.3 IMCL/H2O and -1.7±13.1 IMCL/Cr; P=0.02 and P=0.04)
  • There were no significant differences in percentage change in SO-IMCL or extramyocellular lipids (EMCL)
  • There were no significant differences in pre- and post-training fat mass, lean mass, fat-free mass or body weight.
Author Conclusion:
  • CHO supplementation after an overload running training program, followed by an intensive running protocol, increased IMCL stores. This may have enhanced post-exercise recovery and prevented performance deterioration.
  • CHO supplementation was also effective in the intermittent running session, resulting in lipolytic suppression demonstrated by unchanged FFA levels, increased insulin and a lower post-exercise GH response.
Funding Source:
Reviewer Comments:
  • The authors state that strengths of this study are its design [RCT, long-term (nine days)], study population and place (elite runners in training camp), robust techniques (MRS and DXA for the evaluation of IMCL and body composition) and determination of a variety of blood hormones
  • The authors did not state any limitations to this study, which in itself is a limitation
  • Exclusion criteria and recruitment were also not described by the authors, nor how study participants were randomized to the intervention.


CHO: Carbohydrate
IMCL: Intramyocellular lipids
EMCL: Extramyocellular lipids
H-MRS: Magnetic resonance spectroscopy
Cr: Creatine
FFA: Free fatty acid
GH: Growth hormone
TA: Tibialis anterior
SO: Soleus
DXA: Dual-energy X-ray absorptiometry
Vm3km: Mean three-km velocity

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? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? ???
  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) No
  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)? Yes
  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? N/A
9. Are conclusions supported by results with biases and limitations taken into consideration? No
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? No
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