NAP: Recovery (2014)


Rowlands DS, Thorp RM, Rossler K, Graam DF, Rockell MJ. Effect of protein-rich feeding on recovery after intense exercise. Int J Sport Nutr Exerc Metabol. 2007; 17: 521-543.

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

To determine the effect of enriching the protein content of carbohydrate-rich fat-containing food after interval training on muscle damage, soreness and performance the following morning. 

Inclusion Criteria:

Male endurance-trained cyclists.

Exclusion Criteria:

Not discussed.

Description of Study Protocol:

Randomized crossover trial:

  • Day One: Consumed low-PRO diet, with final meal consumed four hours prior to exercise. In the lab, subject completed 2.5-hour cycling intervals:
    • 12-minute warm-up at 30% Wmax
    • Five minutes at 40% Wmax
    • Five minutes at 50% Wmax
    • 10x2 minutes at 90% Wmax, 12x2 minutes at 80% Wmax alternated with two-minute recovery periods at 50% Wmax, finishing with 3x5 minutes at 70%, interspersed with 3x5 minutes at 50%. 
  • Day Two:
    • Small breakfast was consumed (50g cereal bar)
    • 15 minutes later, cycling began:
      • Warm-up and six two-minute intervals at 80% Wmax, alternated with two-minute recovery periods
      • Performances test consisted of 10 sprints, alternated with 10 recovery periods at 40% Wmax.   

Blinding Used



  • Protein-enriched, carbohydrate-rich recovery supplement and an isocaloric high-carbohydrate control. Each was consumed in units, the first immediately after the first blood draw on Day One and then in 30-minute intervals from 180 minutes after the blood draw, having the last unit within one hour of leaving the lab.
  • Control and PRO were a milk-coated bar and milk-like drink formulation closely resembling each other in taste, smell and texture. PRO provided 1.6g CHO, 0.8g protein and 0.29g fat per kg of FFM per hour and control 0.12g protein, 2.35g CHO and 0.29g fat per kg of FFM per hour. Bar and drink were given every 30 minutes, starting immediately after exercise on Day One for four hours.

Statistical Analysis

The effects of the protein-enriched intervention (PRO) relative to the control condition on the dependent outcome variables were estimated by an analysis of variance for mixed and random effects. The effect of treatment (fixed effect) and the error of measurement (random effect) in sprint mean power and perceptual parameters during the performance test were determined from an integrated model including both the intervention trials (One and Two) and a repeat of the PRO (Trial Three). Most dependent variables, except perceptual parameters, were analyzed after log transformation to reduce or eliminate effects of non-uniformity of error. Quantitative mixed linear models were applied independently to two time-series data sets and included blood samples during the first three hours of the four-hour post-exercise recovery period and the sprint-performance test procedure. 

Data Collection Summary:

Timing of Measurements

  • Blood at approximately five minutes post-exercise and every 30 minutes for the following 120-minute recovery period, with a final sample at 180 minutes on Day One
  • On Day Two, fasting blood is taken:
    • At 15 minutes after a small breakfast
    • During the test at the end of warm-up
    • At 20 seconds to 60 seconds after Sprints One, Four, Seven and 10.
  • Perceived exertion after Sprints One, Four, Seven and 10.

Dependent Variables

  • Perceived exertion: Continuous Likert scale from one (nothing) to nine (maximum) for sensation of tiredness, limb soreness, ability to sprint and level of effort during the sprints and if nauseous
  • Lactate and glucose: Automated system 
  • Muscle damage: Creatine phosphokinase
  • Plasma insulin and total testosterone: Double-antibody radioimmunoassay
  • Growth hormone: Coated-tube assay.

Independent Variables

Protein-enriched, carbohydrate-rich recovery supplement and an isocaloric high-carbohydrate control.  

Control Variables

  • Cyclists recorded training and diet for 10 days and two days, respectively, before the first testing block and then repeated the same training and diet preceding the second block of testing to replicate pre-conditioning
  • On Day One, cyclists ate a low-protein diet up until four hours before completing a ride of 2.5 hours of intervals
  • On Day Two, the cyclists ate a small breakfast and then completed the performance tests of 10 sprints, alternated with 10 recovery periods at 40% Wmax
Description of Actual Data Sample:
  • Initial N: Ten males
  • Attrition (final N): Ten
  • Age: 35±10 years.

Other Relevant Demographics

  • VO2max: 4.9±0.6L per minute
  • Peak power output: 360±30W
  • Training for 7.5±3.5 years with a weekly average of 10.3±2.6 hours the previous six months. 


  • Height: 180±4cm tall
  • Body mass: 76±4kg
  • Estimated fat-free mass (FFM): 68±2kg
  • Body fat: 10±4%.
Summary of Results:


  • Effects of treatment on sprint power was unclear
  • The cyclists reported substantially lower general tiredness (P=0.05) and possible reduction in leg soreness (P=0.07) and increased leg strength (P=0.33) during the sprints in the PRO
  • Glucose was 10% and 4% lower during recovery and in sprints, respectively, in PRO than in control. Lactate was substantially higher in control. The decline in lactate from Sprint One to Ten in control was 25% greater (90% CI: ±23%, very likely; P=0.07) relative to the decline in PRO. The change in glucose from Sprint One to Ten was upward of 24% (±12%, almost certain; P=0.007) greater in PRO than control. 
  • Effect of treatment on insulin, cortisol and growth hormone was unclear. Recovery testosterone was substantially increased in PRO
  • Creatine kinase was 33% lower (90% CI: ±38%, decrease possible; P=0.14) in PRO than control.   
Author Conclusion:

Protein-enriched recovery feeding had no clear effect on next-day performance. 

Funding Source:
Fonterra Innovation Palmerston North; Bronston and Jacobs Auckland; Nice and Natural Auckland (Product support)
Food Company:
Pharmaceutical/Dietary Supplement Company:
In-Kind support reported by Industry: Yes
Reviewer Comments:
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? 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.) 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.) N/A
  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? 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