EAL

NAP: Recovery (2007)

Citation:

Siu PM, Wong SH, Morris JG, Lam CW, Chung PK, Chung S. Effect of frequency of carbohydrate feedings on recovery and subsequent endurance run. Med Sci Sports Exerc. 2004 Feb; 36 (2): 315-323.

PubMed ID: 14767257

Study Design:

Randomized Crossover Trial

Class:

A - Click here for explanation of classification scheme.

Quality Rating:

NEUTRAL: See Quality Criteria Checklist below.

Research Purpose:

The authors tested the hypothesis that small and frequent feedings, compared to one large bolus feeding, of a high-glycemic index meal during a four-hour recovery after 90 minutes of sub-maximal running would increase subsequent endurance capacity.

Inclusion Criteria:

Inclusion criteria not listed, but participants were administered pre-trial tests: Speed-oxygen uptake test, a VO_2max test and a lacate-speed test and measurement of post-prandial glycemic response to be sure participants would respond normally to a high-glycemic index meal.

Exclusion Criteria:

None listed
Participants self-reported that they did not have a history of diabetes.

Description of Study Protocol:

Recruitment

Data not provided.

Design

A randomized counter-balanced cross-over trial conducted 10 to 14 days apart
A 90-minute constant pace run at 70% VO_2max was followed by a four-hour recovery, which was followed by a subsequent run to exhaustion at the same intensity as the original run. The trials were conducted in the exercise physiology lab.

Blinding Used

The authors report that the purpose of the study was not communicated to participants to avoid bias
Participants could not be blinded to differences in meal size and frequency. The "chief experimenter" was unaware of the treatments. Participants were not told their running times.

Intervention

The hypothesis was that the 'nibbling' pattern would increase endurance capacity, compared to the 'gorging' pattern during recovery.

Statistical Analysis

Student's T-test for paired data
Factorial ANOVA with repeated measures to examine two treatments and among phases within the trial (two-way x time x treatment)
Tukey's post-hoc test to examine significant differences; statistical significance set at 0.05.

Data Collection Summary:

Timing of Measurements

Blood glucose concentration (during recovery at 15, 30, 60, 75, 90, 120, 135, 150 and 180 minutes after first intake and hourly venous blood sampling)
Perceived rating of gut fullness (during recovery at 15, 30, 60, 75, 90, 120, 135, 150 and 180 minutes after first intake).

Dependent Variables

Endurance run time to exhaustion in the second run
Total substract oxidation
Three-day macronutrient intake before the first trial, measured by three-day weighed food records
Change in urine volume
Body weight measured in the nude before and after each run
Pre-exercise, post-exercise and recovery capillary and venous blood samples were analyzed for blood lactate and glucose concentrations (measured by lactate analyzer), serum insulin, FFA, glycerol and cortisol concentrations
RER
HR (monitored continuously by Sport Tester PE 4000)
RPE (ratings of perceived exertion)
PT (ratings of perceived thirst)
AD (ratings of abdominal discomfort).

Independent Variables

"Nibbling" pattern vs. "Gorging" pattern
During recovery, participants consumed high-glycemic index foods providing 1.5g carbohydrate per kg of body mass. Foods were prepared by a sports dietitian and included baked potato, margarine, tomato sauce, low-fat processed cheese, 7-up and Rice Krispies. The energy content was 2.4±0.1MJ, the CHO contributed 65% of energy (93.3±2.6g CHO), 15% protein (22.5±0.5g) and 20% fat (12.4±0.2g).
Foods in the "gorging" pattern were consumed 20 minutes after the run. Foods in the "nibbling" pattern were consumed in three equal portions starting 20 minutes after the run with all foods eaten within 20 minutes of the session. Water equal to 150% body mass lost during the original run was consumed at 30-minute intervals in the first three hours of recovery.

Description of Actual Data Sample:

Initial N: Eight trained male runners
Attrition (final N): Eight
Age: Mean: 30±2.1 years
Ethnicity: Not stated, but study conducted in Hong Kong
Other relevant demographics: All subjects were involved in endurance running and were accumulating at least 50km of running per week
Location: University of Hong Kong.

Summary of Results:

Variables	Gorge (Mean±SEM)	Nibble (Mean±SEM)	Statistical Significance of Group Difference
Run time to exhaustion (minutes)	68.1±8.2	66.8±8.7	NS
Dietary analysis - energy (MJ)	12.7±1.2	13.6±1.8	NS
Dietary analysis- carbohydrate (percentage kcals)	65.0±2.0	64.0±2.0	NS
Dietary analysis- protein (percentage kcals)	17.0±0.6	18.0±1.1	NS
Dietary analysis- fat (percentage kcals)	18.0±2.0	18.0±2.0	NS
Capillary blood glucose concentrations, (mmol per minute per L)	154±24	194±27	NS
serum insulin at 60 minutes, mU/L	27.9 4.6	16.6 2.6	P<0.05
CHO oxidation (CHO utilized during 2nd run), grams	94.4±11.4	117.6±10.6	P<0.05
Fat oxidation (fat utilized during 2nd run), grams	55.9±8.0	44.0±8.6	P<0.01

Other Findings

The run time during T2 was similar between trials (68.1±8.2 vs. 66.8±8.7 minutes, P>0.05)
However, CHO utilization was lower and fat oxidation was higher during T2 in the Gorging trial, compared to the Nibbling trial (CHO: 94.4±11.4 vs. 117.6±10.6g, P<0.05; Fat: 55.9±8.0 vs. 44±8.6g, P<0.01, respectively).
No difference in blood lactate concentrations between the two feeding patterns during either run or the recovery period
No differences in serum glycerol and cortisol
No differences in the perception scales, heart rate or VO₂
Plasma sodium and potassium were maintained during exercise and recovery in both trials
No differences in cumulative urine output during recovery between the two groups
Subjects achieved a high level of rehydration after recovery (no significant differences)
Serum FFA at 180 minutes in recovery period of the single feeding was higher than the single feeding (P<0.05)
No direct measures of muscle glycogen.

Author Conclusion:

In conclusion, these results suggest that serial consumption of a high-glycemic index meal during a four-hour recovery increased reliance on CHO oxidation for energy provision during a susequent exhaustive run, when compared to a single feeding
However, there was no difference in run time after the recovery between the two feeding patterns.

Funding Source:

Government:

Hong Kong Sports Development Board

Reviewer Comments:

Inclusion criteria, exclusion criteria and recruitment methods were not well-defined
Multiple comparisons were made, so we should use caution in interpreting the few 'significant' results.

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?		N/A
	3.1.	Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT)	N/A
	3.2.	Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?	N/A
	3.3.	Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.)	N/A
	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?	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?	???
	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?	???
	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?	???
	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)?	Yes
	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?	???
	8.7.	If negative findings, was a power calculation reported to address type 2 error?	No
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?	No
	10.2.	Was the study free from apparent conflict of interest?	Yes