EAL

NAP: Recovery (2007)

Citation:

Van Loon LJC, Schrauwen-Hinderling VB, Koopman R, Wagenmakers AJM, Hesselink MKC, Schaart G, Kooi ME, Saris WHM. Influence of prolonged endurance cycling and recovery diet on intramuscular triglyceride content in trained males. Am J Physiol Endocrinol Metab. 2003; 285: E804-E811.

PubMed ID: 12783774

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 investigate the effects of endurance exercise and recovery diet on intramuscular triglyceride content in the vastus lateralis muscle.

Inclusion Criteria:

None specifically mentioned.

Exclusion Criteria:

None specifically mentioned.

Description of Study Protocol:

Recruitment: Methods not specified
Design: Randomized crossover trial
Blinding used: Lab tests.

Intervention

Standardized diet for three days, followed by two recovery days of either normal diet (39% of energy as fat) or typical carbohydrate-rich diet (24% of energy as fat)
Interventions separated by three weeks.

Statistical Analysis

Statistical significance of differences between trials was assessed by paired T-tests
Repeated-measures ANOVA was applied to assess statistical differences over time within trials
Scheffe post-hoc test was applied to locate any differences over time
Simple regression analysis was performed on mixed-muscle intramuscular triglyceride content, as determined by magnetic resonance spectroscopy and average muscle fiber intramuscular triglyceride content, as determined by quantitative fluorescence microscopy (corrected for muscle fiber type composition).

Data Collection Summary:

Timing of Measurements

Subjects were provided with a standardized diet for three days, after which they performed a three-hour exercise trial at a 55% maximum workload
Intramuscular triglyceride content and blood samples were measured before and immediately after exercise and after 24 and 48 hours of recovery, during which subjects consumed either normal-fat diet or low-fat, carbohydrate-rich diet for two days
Interventions were separated by three weeks.

Dependent Variables

Intramuscular triglyceride content measured through magnetic resonance spectroscopy and oil red O epifluorescence
Total fat and CHO oxidation rates determined through gas exchange measurements
Muscle biopsies
Blood samples analyzed for plasma FFA, free glycerol and triglyceride.

Independent Variables

Standardized diet (30% fat) for three days prior to exercise testing, meals were provided with total energy intake and macronutrient composition calculated from remains
Subjects asked to refrain from heavy physical labor or exercise during standardization periods
Two recovery days of either normal diet (39% of energy as fat) or typical carbohydrate-rich diet (24% of energy as fat).

Control Variables

Muscle fiber type composition.

Description of Actual Data Sample:

Initial N: Nine male cyclists
Attrition (final N): Nine males
Age: Mean, 23.9±0.8 years
Ethnicity: Not mentioned
Other relevant demographics: Mean BMI, 21.9±0.6
Location: The Netherlands.

Summary of Results:

	Standardization Pre-Exercise	Low-Fat Recovery	Normal-Fat Recovery
Energy intake, MJ per day	14±0.2	14±0.5	15±0.4
Fat intake, percentage	30±0.3	24±1.7	39±0.3
CHO intake, percentage	56±0.8	62±2.5	49±0.3
Protein intake, percentage	13±0.2	14±0.3	14±0.1
Energy expenditure, MJ		11.7±0.21	11.7±0.28
Fat oxidation, grams		100±7	88±3
CHO oxidation, grams		469±20	502±20
Fat oxidation, percentage		35±2	31±1
CHO oxidation, percentage		65±2	69±1
IMTG content, percentage, type I fibers		1.39±0.21	2.09±0.002, P<0.05
IMTG content, percentage, type II fibers		0.51±0.11	0.66±0.12

Other Findings

During exercise, intramuscular triglyceride content decreased by 22.6±5.3% in the low-fat diet and 20.4±3.7% in the normal-fat diet, with no differences observed between trials
During recovery, intramuscular triglyceride content increased significantly in the normal-fat diet only, reaching pre-exercise levels within 48 hours
There was significantly higher intramuscular triglyceride content in the normal-fat diet, compared with the low-fat diet, with differences restricted to the type I muscle fibers (2.1±0.2 vs. 1.4±0.2% area lipid staining, respectively).

Author Conclusion:

In summary, the present study shows that intramuscular triglyceride content in the vastus lateralis muscle is reduced substantially after prolonged endurance cycling exercise in trained male athletes
When a normal-fat diet is used, intramuscular triglyceride content is subsequently repleted within 48 hours of post-exercise recovery
In contrast, repletion is impaired substantially when a low-fat, carbohydrate-rich athlete's diet is used
These results imply that carbohydrate-rich diets, as generally recommended to endurance athletes, are insufficient in providing ample substrate for intramuscular triglyceride repletion in male athletes, which could prove to result in sub-optimal performance capacity during periods in which prolonged endurance exercise trials are performed repeatedly.

Funding Source:

University/Hospital:

Maastricht University, University Hospital Maastricht (both Netherlands)

Reviewer Comments:

Recruitment methods, inclusion criteria and exclusion criteria were not defined.

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?	No
	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?	N/A
	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?	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)?	Yes
	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