NAP: Recovery (2014)


Thomson JS, Ali A, Rowlands DS. Leucine-protein supplemented recovery feeling enhances Subsequent cycling performance in well-trained men. Appl Physiol Nutr Metab. 2011; 36 (2): 242-253

PubMed ID: 21609286
Study Design:
Randomized Crossover Trial
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Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:
The purpose of this study was to determine whether a practical leucine-protein, high-carbohydrate post-exercise feeding regimen could improve recovery, as measured by subsequent cycling performance and mechanistic markers, relative to control feeding.
Inclusion Criteria:
  • Male cyclists and triathletes
  • Subjects were screened for precluding health conditions and gave written consent to participate.
Exclusion Criteria:

Not discussed.

Description of Study Protocol:


Not discussed.


  • This is a double-blind, placebo-controlled crossover comprising two nine-day blocks of exercise training followed by a performance test
  • A two-week wash-out between blocks. Beginning two weeks prior to the first experimental block, preliminary tests were conducted over three consecutive days.
  • Subjects performed two- to 2.5-hour interval training bouts on three consecutive evenings, ingesting one of two supplements for 1.5 hours post-exercise
  • The diet during the experimental period was controlled, energy and macronutrient intake was balanced and protein intake clamped at 1.6g per kg-1 per day-1
  • The alternate supplement was provided the next morning, thereby isolating the postexercise nutrition effect. Following 39 hours of recovery, cyclists performed a repeat-sprint performance test.
Blinding Used

Isocaloric nutrition protocols delived as supplement beverage and additional food items during first 90 minutes of recovery:
  • Leucine-protein, high-carbohydrate nutrition (0.1g/0.46g/1.2g/0.2g per kg-1 per hour-1 leucine, protein, carbohydrate and fat, respectively)
  • Control (0.06/g1.6g/0.2g per kg-1 per hour-1 protein, carbohydrate and fat, respectively).
Statistical Analysis
  • The effects of treatment on dependent outcome variables were estimated with mixed linear modeling
  • Dependent variables were analyzed after log transformation to reduce effects of heteroscedasticity, except nitrogen balance data, which had negative values that were undefined with log transformation
  • Outcomes from the log transformed analyses were expressed as percentage or fold differences with appropriate geometric measures of variation or error
  • An analysis of the likelihood of a substantial increase, decrease or negligible effect from the two-tailed Students T-distribution was performed with likelihoods ordered into cut-offs and inferred as:
    • Under 1%: Almost certainly not
    • 1% to 5%: Very unlikely
    • 5% to 25%: Unlikely
    • 25% to 75%: Possible
    • 75% to 95%: Likely
    • 95% to 99%: Very likely
    • Over 99%: Almost certain.
  • Majority (more than 50%) of the uncertainty lies between the threshold for a substantial increase and decrease: The likelihood of the effect being trivial (negligible, unaffected) is qualified
  • Effects were described as unclear or inconclusive if the confidence interval overlapped into both positive and negative values.
Data Collection Summary:

Timing of Measurements

  • Timed 24-hour urine samples were collected following first void immediately post-exercise on Day Minus-Four until immediately prior to the performance test on Day Zero for analysis of nitrogen excretion
  • Regional sweat collection, using gauze pads at the chest and abdomen, was undertaken during training rides on Days Minus Three and Minus Two for quantification of exercise sweat nitrogen content
  • On Day Minus Four, blood was collected for analysis of the muscle damage markers creatine kinase (CK) and lactate dehydrogenase (LDH) and blood was also collected immediately following and 30, 60, 90 and 120 minutes after exercise for the representative plasma amino acid concentrations.
  • Vein punctures were taken prior to exercise on Days Minus Three, Minus Two and Zero for analysis of CK and LDH. Psychometric data, soreness and blood were collected
  • Performance was evaluated via analysis of sprint mean power in a repeat-sprint protocol comprising 10 maximal sprints (typical range, 1.5 minutes to three minutes), interspaced with standardized recovery periods (5.43 minutes) at 40% Wmax
  • The nutritional intervention was ingested over the first 90 minutes of the recovery periods from exercise on Days Minus Four to Minus Two
  • Each block started with three days of reproduced standardized lead-in training followed by a rest day: Training on Days Minus Eight and Minus Seven was conducted in the field on a standardized course with intensity maintained by the subject using heart rate; Day Minus Six was a two-hour controlled ride in the laboratory at 50% of peak power
  • During the four-day lead-in period, training and diet was recorded using a diary, which was checked by researchers and returned to the subject as the schedule for replication over the same period during the second arm of the crossover. The cyclists then completed three consecutive days of controlled high-intensity interval training (Test Days Minus Four, Minus Three, Minus Two) in the laboratory, a rest day (Day Minus One) and then the performance test (Day Zero).
 Dependent Variables
  • Sprint power
  • Perceived overall tiredness during the sprints
  • Perceptions of leg tiredness and soreness
  • Creatine-kinase concentration
  • Lactate dehydrogenase and pressure-pain threshold
  • Anger and other moods
  • Plasma leucine and essential amino acid
  • Net nitrogen balance.

Independent Variables

  • Leucine-protein
  • High-carbohydrate nutrition or isocaloric control.

Contol Variables

  • Controlled diet during testing
  • Training sessions
  • Timing of measurments and consumption of intervention.
Description of Actual Data Sample:
  • Initial N: 10 males
  • Attrition (final N): 10
  • Age: 33±9 years
  • Ethnicity: N/A.

Other Relevant Demographics

  • Average maximal oxygen uptake (VO2max) and peak power outputs were (mean ±SD) 68.2±8.3ml per kg-1 per min-1 and 343±27W, respectively
  • Subjects performed 13.2±4.4 hours per week-1 and 8.1±2.5 hours per week-1 of aerobic training and cycling-specific training, respectively.

Body mass of 76±5 kg.

New Zealand.

Summary of Results:

Key Findings

  • The leucine-protein supplemented meal led to large increases in total (24% to 90%; CL, ±20%) and essential amino acid concentrations (47±39%) and very large increases in leucine concentration (3.0±2.8-fold), relative to the control
  • The leucine-protein supplement reduced perceived overall tiredness during the performance test by 13% (90% CL, ±9.2%), but effects on ratings of perceived exertion, leg tiredness, muscle soreness, and leg soreness were trivial
  • Post-exercise leucine protein ingestion improved mean sprint power by 2.5% (99% confidence limit, ±2.6%; P=0.013) and reduced perceived overall tiredness during the sprints by 13% (90% confidence limit, ±9.2%), but perceptions of leg tiredness and soreness were unaffected
  • Before exercise, creatine-kinase concentration was lowered by 19% (90% confidence limits, ±18%), but lactate dehydrogenase and pressure-pain threshold were unaltered
  • There was a small reduction in anger (25±18%), but other moods were unchanged
  • Plasma leucine (three-fold) and essential amino acid (47%) concentrations were elevated post-exercise
  • Net nitrogen balance trended mildly negative in both conditions (mean ±SD): Leucine-protein, -20±46mg per kg1 per 24 hours; control, -25±36mg·kg1 per 24 hours
  • Differences in vigor, tension, confusion and depression subscales were trivial or unclear
  • Leucine-protein enriched supplement combined with high-carbohydrate meals that were ingested following high-intensity interval training for a period of three days led to a small enhancement of subsequent high-intensity cycling performance
  • A small reduction in CK activity that was suggestive of reduced disruption to skeletal muscle integrity or faster repair over the three-day intense training block was associated
  • The leucine-protein supplementation led to a small reduction in anger throughout the training period and a small reduction in fatigue following the hardest training session
  • Supplementing post-exercise high-carbohydrate meals with a leucine-protein rich beverage during a three-day block of intense cycling in the laboratory enhanced subsequent repeated-sprint performance
  • Twenty-four hour energy, leucine and macronutrient intake was balanced, suggesting that the supplemental leucine and protein exerts its effect when ingested within the first 90 minutes after exercise
  • The improved recovery might be associated with lower disruption to skeletal muscle integrity or to minor change in mood state.
Author Conclusion:
Combining a high-carbohydrate post-exercise diet with a leucine-protein-rich supplement may be beneficial following periods of intense endurance training or competition, when dietary protein intake is mildly below requirement and may attenuate muscle membrane disruption in well-trained male cyclists.
Funding Source:
Fonterra, New Zealand, for ingredient
Pharmaceutical/Dietary Supplement Company:
University/Hospital: Post-Graduate Support Grant from the Institute of Food, Nutrition, Human Health
Reviewer Comments:
  • Very small sample size
  • It is not clear whether there is any carry-over effect
  • It is not a representative sample
  • Further studies are required in a large sample.
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? N/A
  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? N/A
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.) N/A
  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? N/A
  4.1. Were follow-up methods described and the same for all groups? N/A
  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%.) N/A
  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? 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? N/A
  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