NAP: Recovery (2014)


Cockburn E, Stevenson E, Hayes P, Robson-Ansley P, Howatson G. Effects of milk-based carbohydrate-protein supplement timing on the attenuation of exercise-induced muscle damage. Appl Physiol Nutr Metab. 2010; 35: 270-277.

Study Design:
Non-Randomized Controlled Trial
C - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:

The purpose of this study was to examine whether consuming milk-based carbohydrate-protein (CHO-P) drink before muscle-damaging exercise is more beneficial in attenuating exercise-induced muscle damage (EIMD) than consuming it after.

Inclusion Criteria:
  • Male
  • Regular participation in sports.
Exclusion Criteria:

Not discussed.

Description of Study Protocol:


Not discussed.


  • Non-randomized trial: Participants were assigned to one of four groups and matched for physical abilities assessed prior to trial beginning (concentric knee flexion peak torque). All participants completed exercise intervention following warm-up and consumption of assigned beverage. 
  • Participants consumed 1,000ml of the assigned beverage within 30 minutes and then immediately completed a bout of exercise dsesigned to induce acute muscle damage. Upon completion of exercise, they immediately consumed 1,000ml of their beverage within 30 minutes. At 24 horus post-exercise, consumed 1,000ml of the assigned beverage.

Blinding Used



Assignment to one of four beverage groups:

  • PRE: Milk-based CHO-P consumed before muscle-damaging exercise and water consumed at all other time-points
  • POST: Milk-based CHO-P consumed immediately after muscle-damaging exercise and water consumer at all other time-points
  • TWENTY-FOUR: Milk-based CHO-P consumed 24-hours after muscle-damaging exercise and water consumed at all other time-points
  • CON: Water consumed at all time- points.

Supplement contained 707kcals, 33.4g protein, 118.2g carbohydrate and 16.4g fat per liter. Protein was casein and whey. 

Exercise regimen followed five-minute warm-up on a cycle ergometer, isokinetic muscle performance measures and three drop jumps and consumption of 1,000ml of their allocated beverage (supplement or water) within 30 minutes.

Muscle-damaging exercise targeted the hamstrings. Study participants completed six sets of 10 repetitions of unilateral eccentric-concentric knee flexions, resting for 90 seconds between sets. The process was completed for both legs and took approximately 30 minutes.

Degree of active delayed onset of muscle soreness (DOMS) was assessed at warm-up (baseline) and while conducting maximal knee flexions on a scale of zero to 10.

Statistical Analysis

  • Uncertainty of outcomes as 90% confidence intervals (CI), making probabilistic magnitude-based inferences about the true value of outcomes
  • The analysis of most dependent variables were conducted on log-transformed valued to overcome heteroscedaltic error. Muscle soreness data were not log-transformed due to interval scaling.
  • One-way analysis of variance (ANOVA) was used to assess group differences at baseline.
Data Collection Summary:

Timing of Measurements

  • At 24, 48 and 72 hours after muscle-damaging exercise, participants repeated baseline testing: Analog scale for active muscle soreness and venous blood sample
  • CK: Prior to exercise and at 24, 48 and 72 hours post-exercise
  • Active muscle soreness: Prior to exercise and at 24, 48 and 72 hours post-exercise.

Dependent Variables

  • Reactive strength index: Drop jump from 43cm onto force place. Jump height (cm)/contact time(s)
  • Serum creatine kinase (CK): Venipuncture from forearm vein
  • Peak torque: Best repetition for six concentric maximal-effort knee flexion.

Independent Variables

Timing of ingestion of CHO-P supplement: Prior to exercise, immediately following exercise, 24 hours after exercise vs. water placebo.

Control Variables

  • Timing of measurements
  • Subject characteristics
  • Avoidance of caffeine, nutritional supplements, alcohol or anti-inflammatory drugs prior to study
  • Avoidance of strenuous physical activity 48 hours prior to study
  • Participants were tested in the morning to minimize diurnal variation.
Description of Actual Data Sample:
  • Initial N32 males
  • Attrition: 32 males
  • Age: 20±2 years
  • Ethnicity: Not discussed
  • Other relevant demographics: Not reported
  • Anthropometrics: There were no significant differences between subjects for age (20±2 years), height (180.3±4.8cm) or body mass (78.5±9.0kg)
  • Location: United Kingdom.
Summary of Results:

Key Findings

  • DOMS and RSI: As assessed by delayed onset of muscle soreness (DOMS), peak torque and reactive strength index (RSI), it was most beneficial to consume CHO-P supplement POST and 24 hours following training than either before training or as compared to placebo (water)
  • Peak torque: There was a likely benefit of POST consumption of supplement and at 24 hours in limiting decreases in peak torque, compared with PRE and CON
  • CK: There was a benefit of both POST and at 24 hours, compared with CON in blunting increase in CK between baseline and 48 hours.

Other Findings

Active muscle soreness peaked at 48 hours for all groups.
Author Conclusion:
  • The primary finding of the study was that consumption of milk-based CHO-P supplement immediately or 24 hours following muscle-damaging exercise may hasten recovery at 72 hours
  • CHO-P supplement comsumption immediately and 24 hours post-exercise was beneficial in blunting increases in active DOMS and decreases in muscle performance over 48 hours, compared with pre-exercise supplementation.



Funding Source:
My Goodness Ltd - provided supplement and contributed to costs
Pharmaceutical/Dietary Supplement Company:
Reviewer Comments:
  • Assessment of other milk or protein shake consumption was not discussed: It is possible that study groups were not equivalent in their dairy consumption (groups were equivalent for total calories and macronutrient distribution)
  • Placebo was not matched for calories: It is difficult to conclude that the benefits of milk-based CHO-P were not due simply to the additional calories.
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? No
2. Was the selection of study subjects/patients free from bias? No
  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? ???
  2.3. Were health, demographics, and other characteristics of subjects described? No
  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) ???
  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? ???
  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? ???
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? No
  6.6. Were extra or unplanned treatments described? No
  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? Yes
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? N/A
  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? ???
  10.1. Were sources of funding and investigators' affiliations described? ???
  10.2. Was the study free from apparent conflict of interest? ???