NAP: Recovery (2014)


Vieillevoye S, Poortmans JR, Duchateau J, Carpentier A, Effects of a combined essential amino acids/carbohydrate supplementation on muscle mass, architecture and maximal strength following heavy-load training. European Journal of Applied Physiology, 2010; 110: 479-488.

Study Design:
Randomized Controlled Trial
A - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:

The purpose of this study was to evaluate the effects of an EAA supplementation on muscle mass, architecture and strength in the early stages of a heavy-load training program.

Inclusion Criteria:
  • Healthy males
  • Recreationally active students in physical education or physiotherapy
  • No strength training for six months prior to study.
Exclusion Criteria:
  • Strength training for six months prior to study
  • No other specific exclusion criteria given.
Description of Study Protocol:
  • Recruitment: Not discussed
  • Design: Prospective, randomized controlled trial. Subjects were matched for nutritional protein intake and strength, then randomly assigned to the EAA Supplementation or Placebo Group. Subjects participated in twice-weekly strength training sessions.  
  • Blinding used (if applicable): Double-blind.


  • EAA + carbohydrate supplement: A flavored 30-gram mixture provided 15g EAA (11% histidine, 10% isoleucine, 19% leucine, 15% lysine, 3% methionine, 15% phenylalanine, 15% threonine and 12% valine)+15g saccharose (sucrose) and provided 238kcal per day to subjects' diets
  • PLA contained 30g saccharose (sucrose) and the same artificial sweetner as for the EAA supplement and provided 239kcal per day to subjects' diets. There is no mention of an artificial sweetner in the description of the study solution.
  • Supplements were dissolved in 200ml water and consumed supplement (EAA or PLA) twice daily (with breakfast and dinner on non-exercise days and with breakfast and immediately after strength-training on exercise days).

Statistical Analysis

  • Continuous baseline variables are described as the group means ±SD
  • A linear model with a two-way mixed facotrial ANOVA (i.e., groups x time) was used with repeated measures for time
  • Post-hoc tests evaluated with Bonferroni test for multiple comparisons
  • Regression lines were provided using GraphPad Prism 4
  • Statistical significance set at P=0.05.
Data Collection Summary:

Timing of Measurements

Prior to study

  • Dietary intake was assessed by a food questionaire completed over seven continuous days. Protein intake was calculated.
  • Subjects completed two 24-hour urine collections at the same time as they were keeping food records (one weekday and one weekend day). Nitrogen balance was was estimated from protein intake (grams of protein/6.25=grams of N) and urinary nitrogen.
  • Prior to beginning of study period, anthropometric measurements were done to determine height, weight,  muscle mass and muscle architecture and strength testing was done to detrmine muscle strength.

Study period

  • Strength-training was done twice per week over 12 weeks, a total of 24 sessions per subject
  • There was at least one day of rest between strength-training sessions (timing of sessions was individualized for subjects in order to achieve 100% participation).

End of study

  • Repeat anthropometric measurements were done to determine height, weight, muscle mass and muscle architecture and strength testing was done to detrmine muscle strength.

Dependent Variables

  1. Changes in muscle mass: Assessed by anthropometric measurements using method of Lee et al, 2000. Skinfold thickness (S) measured on right side of the body and recorded to nearest 0.1mm with a Harpender calliper. Skinfold thckness measured at triceps, thigh and medial calf, according to standardized anatomic localizations and methods reported by Lohman et al, 1988. Circumference measurements (C) made in the plane orthogonal to the long axis of the body segment being measured, using a flexible standard measruing tape; circumference measurements were made at mid-upper arm, mid-thigh and mid-calf to nearest one mm.
  2. For each skinfold thickness and circumference measured, means of three measurements were used. S was assumed to be twice the subcutaneous adipose tissue thickness. Corrected muscle (including bone) circumferences (Cm) were calculated as Cm=Climb-pS. Corrected muscle circumferences were squared and multiplied by height to obtain a three-dimensional skeletal muscle mass (SMM).
    • Prediction formula for SMM: SM=HT x (k1 x CAG2 + K2 x CTG2 + k3 x CCG2) + k4 x sex x age + k6
      • K1, K2, K3, K4, K5, K6: Constants from multiple regression equation
      • Sex: 1 for male
      • Age measured in years
      • CAG: Corrected circumference for upper arm
      • CTG: Corrected circumference for thigh
      • CCG: Corrected circumference for calf.
  3. Changes in muscle architecture: Architectural changes to gastrocnemius medialis (GM) were assessed from images obtained with a real-time B-mode echograph, using a 13-MHz linear-array probe. Two parameters were measured: Muscle thickness and pennation angle.
  4. Changes in muscle strength: Testing took place at the same time of day before and after strength-training program. Maximal isokinetic force for the standing squat and supine bench press was measured with a dynamometer.

Independent Variables

Placebo or EAA+CHO solution.

Control Variables

  1. Dietary intake
  2. Strength before study
  3. Muscle mass before study
  4. Muscle architecture before study
  5. Age
  6. Weight
  7. Height.
Description of Actual Data Sample:
  • Initial N: 29 males
  • Attrition (final N): 100% completed study
  • Age: EAA, 23.9±2.8 years; PLA, 24.9±5.3 years
  • Ethnicity: Not reported
  • Other relevant demographics: Baseline protein intake was 1.30±0.17g per kg body mass for PLA and 1.32±0.23g per kg body mass for EAA.
  • Height: EAA, 181.0±6.0cm; PLA, 180.5±4.0cm
  • Weight: EAA, 73.6±7.4kg; PLA, 75.5±10.5kg
  • Muscle mass: EAA, 33.0±3.1kg; PLA, 34.9±3.6kg; no significant differences between EAA and PLA Groups
University Libre de Bruxelles, Brussels, Belgium.
Summary of Results:

Key Findings

Changes in muscle mass
Significant increase in muscle mass recorded in both groups

  • PLA: 2.3±2.2% (P<0.01)
  • EAA: +3.3±2.6% (P<0.001)
  • No significant difference between groups.

Changes in muscle architecture (muscle thickness)
Increase in muscle thickness

  • EAA Group only: 20.3±2.0mm to 21.1±2.1mm
  • Change of 3.8±2.8% (P<0.01)
  • Between group significance not noted.

Muscle pennation

  • Significant increase in pennation angle for EAA Group only from 21.2±1.5° to 22.4±1.8°
  • Cchange of 5.6±4.1% (P<0.001)
  • A non-significant increase was shown in PLA Group
  • EAA Group greater than PLA Group (P<0.05),

Changes in muscle strength 

  • Bench press: EAA Group increased from 844±174N to 980±200N; 16.7±8.5%, (P<0.001)
  • Bench press: PLA Group increased from 878±142N to 988±184N; 12.6±11.4% (P<0.001)
  • Squat exercise: EAA Group increased from 1,725±268N to 1,813±230N; 5.8±8.7% (P<0.001)
  • Squat exercise: PLA Group had a non-significant increase
  • No significant difference for strength increase was shown between groups. After normalization of initial strength with initial muscle mass, a negative linear regression between normalized initial strength and the increase in muscular strength after training was found for the EAA Group (R2=0.29, P<0.05).

Nitrogen balance

  • Protein intake during treatment period
    • PLA 96±11g per day
    • EAA 96±16g per day
    • Linear regression analysis indicates achievement of an anabolic status with protein intake of 0.93g per kg of body weight.
    • The difference between nutritional protein intake and nitrogen excretion is shown on a graph (y=7.63x-7.09, R2=0.54, P<0.001).
  • Relation between nitrogen balance at baseline and increase in muscle mass following 12 weeks strength training; linear regression was found for PLA Group only (y=0.799x+0.021, R2=0.63, P<0.01.
Author Conclusion:
  • A combined EAA/CHO supplement had positive effects on changes in muscle architecture; supplementation seemed to be more effective in a subject having a lower nitrogetn balance and/or a lower initial strength
  • There is a delay between the onset of functional adaptations (muscle hypertrophy, architecture changes and strength improvements) and the increase in muscle protein synthesis
  • The authors suggest that dietary protein needs of young active adults are higher than protein recommendations by some national agencies (e.g., Institute of Medicine, USA, Higher Council of Health, Belgium).
Funding Source:
University/Hospital: Universite Libre de Bruxelles, Brussels, Belgium
Reviewer Comments:
  • This was a straight-forward study comparing an EAA/CHO supplement with a CHO supplement in recreational athletes beginning a strength training regimen
  • The results showed improvements in muscle mass and strength in both EAA and PLA Groups, with significant improvements in the EAA Group, but not the PLA Group
  • There were significant differences in muscle architecture changes between groups, but other changes were not reported as significant between groups
  • It would be very interesting to see a study such as this continued for several months to see if there were more between-group differences.
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? Yes
3. Were study groups comparable? N/A
  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? N/A
  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.) Yes
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? Yes
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? N/A
  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? Yes
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? Yes
  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? N/A
  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? Yes
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