EAL

NAP: Training (2014)

Citation:

Chen Y, Wong SHS, et al. Effect of CHO loading patterns on running performance. IJSM 2008; 29: 598-606.

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 examine the influence of 3d iso-kcal CHO loading w tih different glycemic index (GI) and glycemic load (GL) meals on running performance and metabolic responses.

Inclusion Criteria:

Healthy male runners without diabetes.

Exclusion Criteria:

Not reported.

Description of Study Protocol:

Recruitment

Not reported.

Design

Randomized crossover trial, three days CHO-loading with different GI and GL meals after a one-hour exhaustive run, followed by a standardized pre-loaded exercise protocol (one hour at 70% VO_2max followed by 10km TT).

Blinding Used

N/A.

Intervention

Three days CHO-loading with different GI and GL meals, all iso-kcal (3,830kcal per day)

High GI, High GL (HH): 10g CHO per kg per day; GI, 80; GL, 553; 73% CHO; 13% PRO; 14% fat
Low GI, Low GL (LL): 10g CHO per kg per day; GI, 36; GL, 249; 73%; CHO, 13%; PRO, 14% fat
High GI, Low GL (HL): Four grams CHO per kg per day; GI 70, GL 227; 30% CHO, 21% Pro, 49% fat.

Statistical Analysis

Two-factor (trial x time) ANOVA with repeated measures
Tukey's post hoc test for significance.

Data Collection Summary:

Timing of Measurements

After pre-screening to assess glycemic response, three days CHO-loading with different GI/GL meals after a one-hour exhaustive run, followed by a 30-minute run at 70% VO_2max to deplete muscle glycogen
On the subsequent two days of the CHO-loading periods, 20 minutes light training was required
On Day Four, one hour running at 70% VO_2max, and a 10-km TT (main trial) was performed after consuming a standard breakfast after a two-hour rest (durnig which blood samples were collected).

Dependent Variables

Heart rate
CHO and Fat oxidation
RPE, abdominal discomfort, perceived thirst
Serum insulin, FFA, glycerol.

Independent Variables

GI/GL load consumed for three days prior to main trial.

Control Variables

Control of training during study
Timing of measurements
Dietary control three days prior to and morning of test session.

[Note: There was no "control" or "usual intake" meal tested.]

Description of Actual Data Sample:

Initial N: Nine male runners
Age: 20.1±0.8 years
Ethnicity: Not reported; assumed to be Asian, given location
Other relevant demographics: VO_2max, 61.9±2.9ml per kg per minute
Anthropometrics: Body mass, 64.8±5.0kg
Location: Hong Kong.

Summary of Results:

Key Findings

There were no differences in time to complete the TT or RER between the two high-CHO trials (HH and LL), but performance and RER in the LL was improved compared to the HL trial
There were no differences in HR, RPE or perceived thirst among the trials. Abdominal discomfort was lower in the HH trial during the TT, compared to the HL and LL trials.
Blood glu was highest in the HH trial pre-exercise, but was similar to the LL during exercise and recovery
There were no differences in plasma insulin during exercise or recovery among the three trials
There were no differences for serum FFA and glycerol between HH and LL trials
During exercise, blood lactate was higher in the two high-CHO trials (HH and LL) at the end of the TT, compared to the HL trial.

Author Conclusion:

The amount rather than the nature of CHO consumed during three days of iso-kcal CHO-loading may be most overriding factor on subsequent metabolic responses and running performance
Three days of CHO-loading with low GI and low GL is more effective in improving performance, compared to low-CHO diets with high GI/low GL
Regardless of GI and GL, CHO-loading with equally high CHO amount (HH and LL) may produce similar responses during subsequent endurance running.

Funding Source:

Other:

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?		???
	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?	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?		N/A
	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%.)	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?		No
	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?	Yes
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?	Yes
	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)?	No
	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?		???
	10.1.	Were sources of funding and investigators' affiliations described?	No
	10.2.	Was the study free from apparent conflict of interest?	???