EAL

NAP: Recovery (2007)

Citation:

Kimber NE, Heigenhauser GJF, Spriet LL, Dyck DJ. Skeletal muscle fat and carbohydrate metabolism during recovery from glycogen-depleting exercise in humans. J Physiol. 2003; 548 (Pt 3): 919-927.

PubMed ID: 12651914

Study Design:

Non-Randomized Controlled Trial

Class:

C - Click here for explanation of classification scheme.

Quality Rating:

NEUTRAL: See Quality Criteria Checklist below.

Research Purpose:

To examine the utilization of intramuscular triacylglycerol as an energy substrate after exhaustive exercise and provide a more thorough examination of the metabolic changes which occur in skeletal muscle during the recovery period following exhaustive, glycogen-depleting exercise.

Inclusion Criteria:

Endurance-trained males
Considered to be healthy.

Exclusion Criteria:

Did not smoke
Did not take any medication
Had no evidence of cardiovascular or metabolic diseases.

Description of Study Protocol:

Recruitment: Subjects volunteered
Design: Non-randomized clinical trial
Blinding used: Not applicable; lab tests
Intervention: High-carbohydrate-rich meals were consumed at one, four and seven hours of recovery.

Statistical Analysis

Results were analyzed using a one-way ANOVA with repeated measures for the time factor to test for changes in each variable measured during the recovery period
A Newman-Keuls post-hoc test was used if differences between time points were detected.

Data Collection Summary:

Timing of Measurements

Subjects completed an exhaustive bout of exercise (approximately 90 minutes) on a cycle ergometer, followed by ingestion of carbohydrate-rich meals at one, four and seven hours of recovery
Duplicate muscle biopsies were obtained at exhaustion and three, six and 18 hours of recovery.

Dependent Variables

Muscle biopsies from vastus lateralis muscle was analyzed for glycogen, total muscle triacylglycerol, phosphocreatine, creatine, pyruvate, acetyl-CoA and acetylcarnitine
Body mass
Blood sampling for whole blood glycerol, lactate, glucose, lipoprotein lipase, fatty acids and insulin
Gas exchange measurements with metabolic cart.

Independent Variables

Carbohydrate-rich meals (65% to 70% of energy from CHO, 20% from fat, 10% to 15% from protein, average glycemic index of 60 to 65) consumed at one, four and seven hours during recovery
For two days prior to the trial, all subjects consumed a high-CHO diet to maximize glycogen stores
Subjects abstained from exercise and consumption of caffeine and alcohol.

Description of Actual Data Sample:

Initial N: Eight endurance trained males
Attrition (final N): Eight
Age: Mean, 25±3 years
Ethnicity: Not mentioned
Other relevant demographics: Mean weight, 72.7±2.1kg; mean VO_2max 63.1±2.6
Location: Canada.

Summary of Results:

	Exhaustion	Three Hours	Six Hours	18 Hours
IMTG (mmol per kg dry weight)	23.5±3.5	24.6±2.6	25.7±2.8	28.4±3.0
Muscle glycogen (mmol per kg dry weight)	37±11	165±13	250±18	424±22

Other Findings

Dietary composition consisted of an average of 67±0.9% of kcal from CHO, 21±0.8% from fat and 13±0.3% from protein and an average glycemic index of 64.5±0.6. Despite the large intake of CHO during recovery (491±28g or 6.8±0.3g per kg), respiratory exchange ratios of 0.77 to 0.84 indicated a greater reliance on lipid as an oxidative fuel.
However, there was no net intramuscular triacylglycerol utilization during recovery
Intramuscular triacylglycerol content at exhaustion was 23.5±3.5mmol per kg dry weight and remained constant at 24.6±2.6, 25.7±2.8 and 28.4±3.0mmol per kg dry weight after three, six and 18 hours of recovery
Muscle glycogen increased significantly from 37±11mmol per kg dry weight at exhaustion, to 165±13, 250±18 and 424±22mmol per kg dry weight at three, six and 18 hours of recovery (P<0.001)
PDH activation was reduced at six and 18 hours, when compared to exhaustion, but did not change during the recovery period
Acetyl-CoA, acetylcarnitine and pyruvate contents declined significantly after three hours of recovery, compared to exhaustion and thereafter remained unchanged.

Author Conclusion:

In summary, we report that intramuscular triacylglycerol content remains unchanged during recovery from glycogen-depleting exercise in the presence of elevated glucose and insulin levels
It appears that the partitioning of exogenous glucose towards glycogen resynthesis is of high metabolic priority during immediate post-exercise recovery and is supported by the trend towards reduced PDH activity and increased fat oxidation
Plasma fatty acids and possibly plasma triglyceride, as well as intramuscular acetylcarnitine stores are likely to be important fuels for muscle metabolism in the immediate recovery period
However, intramuscular triacylglycerol appears to have a negligible role in contributing to the enhanced fat oxidation during recovery from exhaustive exercise.

Funding Source:

Government:

NSERC, CIHR

Reviewer Comments:

Recruitment methods were not described
Lack of statistical significance may be due to the small subject pool, as IMTG content was on trend for increasing.

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?	Yes
	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)	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)?	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?	No
9.	Are conclusions supported by results with biases and limitations taken into consideration?		???
	9.1.	Is there a discussion of findings?	Yes
	9.2.	Are biases and study limitations identified and discussed?	???
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