EAL

NAP: Recovery (2007)

Citation:

Bloomer RJ, Sforzo GA, Keller BA. Effects of meal form and composition on plasma testosterone, cortisol, and insulin following resistance exercise. Int J Sport Nutr Exerc Metab. 2000; 10 (4): 415-424. PubMed ID: 11099368

Study Design:

Randomized controlled trial

Class:

A - Click here for explanation of classification scheme.

Quality Rating:

NEUTRAL: See Quality Criteria Checklist below.

Research Purpose:

To examine the effects of three meals, varying in energy and macronutrient composition, on plasma levels of insulin, testosterone, cortisol and testosterone:cortisol ratio during 24 hours of exercise recovery.

Inclusion Criteria:

Healthy, currently training males, aged 20 to 25 years, with more than two years' resistance exercise experience.

Exclusion Criteria:

None of the subjects had used anabolic agents in the past.

Description of Study Protocol:

Recruitment: Methods not specified
Design: Randomized controlled trial, repeated measures design
Blinding used: Order of conditions was counterbalanced in double-blind fashion.
Intervention: Four different dietary interventions consumed immediately, two and four hours after exercise, followed by a meal at seven and 12 hours.

Statistical Analysis

Two-way repeated measured ANOVA for conditions and times were done for insulin, testosterone, cortisol and the testosterone:cortisol ratio
Where appropriate, significant interactions and main effects were further evaluated with analyses of simple main effects and Tukey HSD.

Data Collection Summary:

Timing of Measurements

Subjects were given one of three dietary interventions or a placebo immediately, two hours and four hours after a standardized weight training protocol on four days, each separated by one week
Venous blood samples were measured pre-exercise and during 24 hours of recovery (at 0.5, 2.5, 4.5, 8 and 24 hours).

Dependent Variables

Insulin was measured by standard radioimmunoassay
Testosterone was measured with chemiluminescent immunoassay procedure
Cortisol was measured by fluorescence polarization.

Independent Variables

Three dietary interventions or a placebo were consumed immediately, two hours and four hours after post-exercise: Whole food (38g protein, 70g CHO, seven grams fat), a supplemental drink (isocaloric and isonitrogenous to whole food), an isocaloric carbohydrate beverage or a placebo beverage (three grams CHO)
All subjects were given a standardized meal at seven and 12 hours post-exercise
Subjects consumed 500ml of water with each meal
Food intake records were maintained for two days prior to the study to assess dietary adherence to consuming similar meals prior to each testing day.

Description of Actual Data Sample:

Initial N: 10 males
Attrition (final N): 10 males
Age: Mean, 20.7±0.95 years
Ethnicity: Not mentioned
Other relevant demographics: Body fat, 17.28±6.25%
Location: New York.

Summary of Results:

Other Findings

Significant (condition x time) interactions were found for insulin, testosterone and testosterone:cortisol ratio, but not for cortisol (P<0.05).

Insulin: The supplemental drink yielded a greater response for insulin than all other conditions at 0.5 hours and also greater than whole food and placebo through 4.5 hours. Placebo concentrations were lower than any other meal values at 0.5, 2.5 and 4.5 hours into recovery (P<0.05). There were no significant differences at eight or 24 hours.
Testosterone: The placebo beverage demonstrated the greatest values for testosterone and testosterone:cortisol ratio at 2.5 and 4.5 hours post-exercise. There were no significant differences between conditions at either time.
Cortisol: Cortisol did not vary between conditions.

There were no condition effects for insulin, testosterone, cortisol and testosterone:cortisol ratio at eight or 24 hours.

Author Conclusion:

In summary, there appear to be few beneficial effects of varying post-exercise meal form or composition on regulating plasma testosterone and cortisol. These hormones appear to be regulated more by diurnal variations than acute feeding patterns.
Although testosterone:cortisol ratio was highest in the fasted state, the supplemental drink promoted the greatest increase in insulin during the immediate four to five hours post-exercise
The efficacy of a particular post-exercise feeding for optimizing testosterone:cortisol ratio and muscle tissue growth is unclear. However, a mixed-nutrient supplemental drink will promote post-exercise hyperinsulinemia, which may mediate muscle tissue growth and enhance glycogen resynthesis.

Funding Source:

Industry:

Experimental and Applied Sciences

Food Company:

Reviewer Comments:

Recruitment methods were not specified and inclusion and exclusion criteria were not well-defined
Authors note that the differing results between the isocaloric and isonitrogenous whole food meal and supplemental drink may be due to the higher glycemic index, lower molecular weight of the meal and to differing protein sources.

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?		???
	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?	???
	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?	???
3.	Were study groups comparable?		???
	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?	???
	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?	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?	Yes
	6.6.	Were extra or unplanned treatments described?	Yes
	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?	No
	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)?	???
	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