EAL

NAP: Recovery (2007)

Citation:

Stevenson E, Williams C, Biscoe H. The metabolic responses to high carbohydrate meals with different glycemic indices consumed during recovery from prolonged strenuous exercise. Int J Sport Nutr Exerc Metab. 2005 Jun; 15 (3): 291-307.

PubMed ID: 16131699

Study Design:

Randomized crossover trial

Class:

A - Click here for explanation of classification scheme.

Quality Rating:

NEUTRAL: See Quality Criteria Checklist below.

Research Purpose:

To further investigate the metabolic responses to HGI and LGI CHO meals consumed during the early period of recovery from prolonged strenuous exercise.

Inclusion Criteria:

Well-trained recreational athletes, running regularly and able to run for at least one hour continuously at about 70% VO_2max.

Exclusion Criteria:

None specifically mentioned.

Description of Study Protocol:

Recruitment: Methods not described
Design: Randomized crossover trial
Blinding used: Not used; lab tests.

Intervention

Subjects participated in two trials separated by at least seven days
Following overnight fast, subjects completed a 90-minute run at 70% VO_2max
Isocaloric low- (GI=38) or high- (GI=75) glycemic index meals were provided 30 minutes and two hours following cessation of exercise.

Statistical Analysis

ANOVA for repeated measures on two factors (experimental treatment and time) used to analyze differences in the physiological and metabolic responses in both trials
If significant interaction was obtained, Holm-Bonferroni stepwise post-hoc test was used to determine the location of the variance.

Data Collection Summary:

Timing of Measurements

Heart rate monitored continuously
Expired air samples, RPE and blood samples collected every 30 minutes throughout 90-minute run
During recovery, expired air samples and blood samples were taken at 15, 30, 60, 90 and 120 minutes after each meal.

Dependent Variables

Heart rate monitored through telemetry
Blood samples analyzed for hemoglobin, hematocrit, lactate, FFA, glucose, glycerol, insulin, cortisol
Expired air samples
RPE measured through Borg scale.

Independent Variables

Isocaloric low- or high-glycemic index meals were provided 30 minutes and two hours following cessation of exercise
Subjects recorded diet and exercise routine so that it was similar for both trials
Subjects instructed to avoid alcohol, caffeine and smoking
Subjects abstained from vigorous exercise for 24 hours prior to trials.

Description of Actual Data Sample:

Initial N: Eight males
Attrition (final N): Eight
Age: Mean, 22.5±2.3 years
Ethnicity: Not mentioned
Location: United Kingdom.

Summary of Results:

Other Findings

There were no differences between trials regarding the glycogen depleting exercise
The plasma glucose responses to both meals were greater in the HGI trial, compared to the LGI trial (P<0.05)
Following breakfast, there were no differences in the serum insulin concentrations between the trials. However, following lunch, concentrations were higher in the HGI trial, compared to the LGI trial (P<0.05).
There were no significant differences between trials in terms of plasma FFA, glycerol, CHO and fat oxidation rates
Subjects reported higher ratings of gut fullness (P<0.05) and lower ratings of hunger (P<0.05) throughout the recovery period in the low-glycemic index trial, compared to the high-GI trial.

Author Conclusion:

In conclusion, the results of the present study provide further evidence that insulin sensitivity is increased following an acute bout of exercise
In addition, the results suggest that the glycemic index of the carbohydrates consumed immediately after exercise might not be important as long as sufficient carbohydrate is consumed and perhaps provided as small, frequent feedings
The glycemic index of the carbohydrates consumed later in the post-exercise period, however, could be important because of their influence on substrate oxidation
The results of this study suggest that a low-glycemic index diet might be more beneficial for continued utilization of fat during the recovery period
Although muscle glycogen was not measured in the current study, it would be reasonable to speculate that the high insulin concentrations following a high-glycemic index meal could facilitate further muscle glycogen resynthesis later in the recovery period.

Funding Source:

University/Hospital:

Loughborough University

Reviewer Comments:

Inclusion criteria, exclusion criteria and recruitment methods were not well-defined
Muscle glycogen was not measured.

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?	No
	2.2.	Were criteria applied equally to all study groups?	???
	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?		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?	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?	No
	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?		???
	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?	???
	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?	???
	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