NAP: Recovery (2014)


Pritchett, K, Bishop P, Pritchett R, Green M, Katica C. Acute effects of chocolate milk and a commercial recovery beverage on postexercise recovery indices and endurance cycling performance. Appl Physiol Nutr Metab. 2009; 34: 1,017-1,022.

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 examine the effects of post-exercise consumption of a CHO replacement beverage (CRB) vs. chocolate milk (CHOC) on indices on muscle damage, CK and muscle soreness, as well as subsequent time to exhaustion.

Inclusion Criteria:
  • Cyclists and triathletes
  • Minimum of two years' involvement in endurance sports
  • Minimum of six training hours per week
  • 19 to 49 years old.
Exclusion Criteria:
  • Younger than 19 years or older than 40 years of age
  • Cyclist or triathlete with less than two years of involvement in endurance sports and less than six hours of training per week.
Description of Study Protocol:
  • Recruitment: Not described
  • Design: Randomized crossover trial
  • Blinding used: Subjects were blinded to the beverage.


  • Low fat chocolate milk (CHOC) vs. CHO replacement beverage (CRB) given immediately after the first exercise session and two hours into the recovery period
  • The same total amount of CHO was given (1.0g per kg-1 per hour-1) and the beverages were isocaloric (2,488.0±557.9kcal vs. 2,319.6±663.5kcal for CHO vs. CRB, respectively)
  • Water, but no other food or beverage were allowed during the recovery period. 

Statistical Analysis

  • Data as compared using a two-factor (treatment x time) repeated-measures analysis of variance (ANOVA)
  • A Tukey's post-hoc test was applied in the case of a significant F-ratio to locate the differences with the ANOVA
  • One-way ANOVA for repeated measures was used to compare markers of muscle damage (CK) muscle soreness and performance between trials
  • Greenhouse-Geisser corrections were conducted for unequal variance data.   
Data Collection Summary:

Timing of Measurements

Before and 15 hours to 18 hours after counter-balanced exercise on two occasions, separated by one week.

Dependent Variables

  • Creatine kinase: Capillary blood analyzed on a spectrometer
  • Time to exhaustion: On a cycle ergometer at 85% VO2 max  until pedal cadence was slower than 60rpm-1 or the participant could no longer continue
  • Muscle soreness: 10-cm visual analog scale with "no pain at all" at the left end and "unbearable pain" at the right end.

Independent Variables

Low-fat chocolate milk (CHOC) and a CHO replacement drink (CRB). 

Control Variables

  • A high-intensity workout (five minutes cycling at 60% VO2max warm-up, followed by three 10-second "all out" bicycle Wingate sprints, interspersed with 50-second active recoveries, repeated a total of six times) followed 15 to 18 hours later after recovery with a five-minute warm-up on a bicycle ergometer and then cycled at a pre-determined workload to elicit approximately 85% VO2max until exhaustion
  • No coffee or alcohol or exercise for a minimum of 24 hours before testing
  • Dietary intake was to be the same between the two trials as before the study (documented by a food frequency questionnaire and three-day food diary, respectively).
Description of Actual Data Sample:
  • Initial N: 10
  • Attrition (final N): 10
  • Age: 27.1±7.9 years
  • Ethnicity: Not described
  • Other relevant demographics: 55.2±7.2ml per kg-1 VO2max and 367.5±38.7W peak watts
  • Anthropometrics: 176.5±3.6cm in height; 72.1±6.7kg body weight; 9.2±6.7% body fat
  • Location: USA.
Summary of Results:


  • The beverages were identical in CHO and similar in protein and kcals
  • The significant difference in fat content (P<0.001) was not enough to significantly affect the difference in overall calorie content between the beverages
  • There ware no significant differences in macronutrient intake between the two trials
  • Sleep patterns were similar between the two trials
  • All of the subjects preferred the taste and consistency of CHOC
  • There was no significant difference (P=0.91) between trials for cycling time to exhaustion
  • There was no significant difference (P=0.29) for the PRE CK level (CKpre) between the two trials
    • A repeated-measures ANOVA revealed a significant (P<0.05) interaction (treatment x time) for change in CKpre to the POST CK level (CKpost)
    • A significantly higher (P<0.05) was observed for the CRB trial, however there was no significant difference (P=0.35) for CKpost between the two trials.
  • No interaction (treatment x time) for muscle soreness was observed
    • There were no significant difference for PRE muscle soreness (P=0.98) and POST muscle soreness (P=0.48) between the two trials
    • Subjective measures of muscle soreness decreased significantly (P<0.01) from PRE to POST.
Author Conclusion:

There is no difference between CHOC and this CRB as potential recovery aids for cyclists between intense workouts.

Funding Source:
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.) 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? N/A
  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%.) 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? 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