NAP: Recovery (2014)
Beelen M, Van Kranenburg J, Senden JM, Kuipers H, Van Loon LJC. Impact of caffeine and protein on postexercise muscle glycogen synthesis. Med Sci Sports Exerc. 2012; 44 (4): 692-700.
To assess the effect of protein or caffeine co-ingestion on post-exercise muscle glycogen synthesis rates when optimal amounts of CHO (1.2g per kg-1 per hour-1) is consumed.
Male cyclist who cycled at least 100km per week-1 and had a training history of more than three years.
- Cycling less than 100km per week-1.
- Recruitment: Not described
- Design: Randomized crossover trial; three tests separated by at least one week
- Blinding used: Double-blind.
- One of three beverages given in amounts of three ml per kg-1 every 30 minutes during recovery (randomized order):
- CHO only (CHO): 1.2g per kg-1per hour-1 CHO
- CHO+protein+leucine mixture (CHO+PRO): 1.2g per kg-1per hour-1 CHO with 0.2g per kg-1per hour-1 casein protein hydrolysate and 0.1g per kg-1per hour-1 leucine
- CHO+caffeine (CHO+CAF): 1.2g per kg-1per hour-1 CHO with 1.7g per kg-1per hour-1 caffeine.
- All drinks were flavored with 0.05g per L-1 sodium saccharinate, 0.9g per L-1 citric acid and 5.0g per L-1 cream vanilla flavor. CHO source was 50% glucose and 50% maltodextrin. Each drink was labeled with 0.32g per L-1 (U-13C6) glucose.
- Plasma insulin and glucose responses were calculated as area under the curve
- A two-factor repeated-measures ANOVA with time and treatment as factors was used to compare differences between treatments over time
- In case of significant F-ratios, Bonferroni post-hoc tests were applied to locate the differences
- For non-time-dependent variables, a paired Student's T-test was used to compare differences between treatment and control
- The results from the questionnaires were analyzed by the Friedman non-parametric test.
Timing of Measurements
- Questionnaire at five, 175 and 355 minutes
- Blood samples at 15-minute intervals for the first 90 minutes of recovery and every 30 minutes after until 360 minutes
- Muscle biopsy at cessation of exercise and after the final blood sample.
- Gi symptoms and taste of beverage: Questionnaire using a 10-point scale (1=not al all, 10=very, very much; or 1=horrible, 10=very tasty, respectively)
- Muscle glycogen concentration and synthesis rates: Muscle biopsy from the middle region of the vastus lateralis muscle
- Plasma insulin, glucose, lactate, FFA, adrenalin and noradrenalin and caffeine: Blood samples.
- CHO only (CHO)
- CHO+protein+leucine mixture (CHO+PRO)
CHO+caffeine (CHO+CAF) beverage.
- Standardized dinner the evening prior to testing
- No physical exhaustive labor or exercise and diet as constant as possible the two days prior to testing
- A food and activity diary kept during these two days was used to standardize food intake and physical activity before the second and third tests
- Abstinence from caffeine containing food and beverages for two days prior to tests
- Muscle glycogen depletion by intense exercise protocol on a cycle ergometer until pedaling speed could not be maintained at 70% Wmax after pedaling bouts at 90% and 80% Wmax
- Recovery of six hours.
- Initial N: 14 males
- Attrition (final N): 14
- Age: 24±1 years
- Ethnicity: Not described
- Other relevant demographics: Maximal workload capacity (Wmax), 387±11W; VO2max, 61.5±1.2ml per kg per minute
- BW: 71.6±2.5kg
- Body mass index: 21.7±0.4km/m2.
- Location: The Netherlands.
- Total cycling time did not differ between experiments
- All drinks were well tolerated; 95±2% of the total volume of test drink (2.6±0.9 L) was ingested, with no differences between treatments. The main complaints of bloated feeling, belching and urge to urinate were no different between experiments, although the taste of the CHO+PRO was rated significantly lower than the the other two drinks (P<0.01).
- Plasma insulin was higher in CHO+PRO, compared with CHO (P<0.05). Plasma glucose did not differ between experiments. No differences in plasma [U-13C6] glucose enrichments were observed between treatments.
- Plasma lactate over time was lower in CHO+PRO vs. CHO (P<0.012). There were no differences between CHO and CHO+CAF.
- Plasma FF over time was higher in CHO+CAF vs. CHO (P<0.01). There were no differences between CHO and CHO+PRO.
- There were no differences between trials over time in plasma adrenalin. Plasma noradrenaline over time was lower in CHO+PRO vs CHO. There were no differences between CHO and CHO+CAF.
- Plasma caffeine increased significantly (P<0.01) in CHO+CAF and was below detection (P<0.05mg per L-1) in the other two trials
- Post-exercise muscle glycogen did not differ between experiments. After six hours of post-exercise recovery, muscle glycogen increased, but the concentrations were not significantly different between trials.
- Histochemical analyses of muscle biopsies revealed no differences in muscle glycogen content between trials or between Type I and Type II fibers. There was a significant correlation between mixed muscle glycogen, determined by PAS staining and muscle glycogen measured using biochemical assay, with a Pearson correlation coefficient of 0.24 (P<0.01).
Coingestion of an insulinotropic amino acid-protein mixture of caffeine does not further accelerate post-exercise muscle glycogen synthesis when an optimal amount of CHO (1.2g per kg-1 per h-1) is already ingested.
Quality Criteria Checklist: Primary Research
|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|
|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?||Yes|
|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?||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?||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?||Yes|
|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|