EAL

NAP: Training (2014)

Citation:

Camera DM, West DWD, Burd NA, Phillips SM, Garnham AP, Hawley JA, Coffey VG. Low muscle glycogen concentration does not suppress the anabolic response to resistance exercise. J Appl Physiol. 2012; 113: 206-214.

Study Design:

Randomized Controlled Trial

Class:

A - Click here for explanation of classification scheme.

Quality Rating:

POSITIVE: See Quality Criteria Checklist below.

Research Purpose:

To determine the effect of:

Decreased muscle glycogen concentration on the acute anabolic response after resistance exercise performed in the fasted state
The effect of protein and CHO supplementation on muscle cell signaling and myofibrillar protein synthesis rates.

Inclusion Criteria:

Healthy physically fit males
Regular concurrent resistance and endurance training.

Exclusion Criteria:

Female.

Description of Study Protocol:

Design

RCT; after a 48-hour diet and exercise control, subjects performed glycogen-depletion protocol. The next morning, after an overnight fast, a constant infusion of L-ring 13C6 phenylalanine was begun and subjects completed eight sets of five leg press reps at 80%, one rep max. Immediately after the resistance exercise, as well as two hours later, subjects consumed either protein and CHO beverage or a placebo beverage (500ml bolus).

Intervention

Protein and CHO vs. placebo:

Placebo (500ml water, artificial sweetener) vs. protein and CHO beverage (20g whey protein, 40g maltodextrin) consumed immediately after REX and two hours later
The nutrient beverage was enriched with a small amount of tracer, to 6.5% of L-[ring-¹³C₆] phenylalanine.

Statistical Analysis

Two-way ANOVA with Student-Newman-Keuls post-hoc analysis. Data for Western blotting and mRNA abundance were log-transformed prior to analysis. Log-transformed delta values between data time points were also directly compared and converted to Cohen effect sizes (ES).

Data Collection Summary:

Timing of Measurements

Muscle biopsies at rest and one hour and four hours after resistance exercise (REX)
Blood tests at baseline and at regular intervals during post-exercise recovery.

Dependent Variables

Blood glucose, plasma insulin, plasma amino acids, plasma [ring-¹³C₆] phenylalanine enrichments
Muscle glycogen, myofibrillar enriched proteins, RNA, DNA, atrogin, myostatin--muscle biopsy of vastus lateralis of both legs.

Independent Variables

Placebo (500ml water, artificial sweetener) vs. protein and CHO beverage (20g whey protein, 40g maltodextrin) consumed immediately after REX and two hours later. The nutrient beverage was enriched with a small amount of tracer, up to 6.5% of L-[ring-¹³C₆] phenylalanine.

Control Variables
At 48 hours before exercise-depletion session, subjects refrained from exercise training and vigorous physical activity and alcohol and caffeine. At 26 hours before the depletion session, subjects were supplied with a CHO-based diet (9g per kg BM). Glycogen-depletion consisting of one-leg cycling to fatigue (LOW) while the other leg rested (NORM). On following day after an overnight fast, subjects were given a primed, constant infusion of L-[ring-¹³C₆] phenylalanine and then completed eight sets of five unilateral leg press repetitions at 80% IRM.

Description of Actual Data Sample:

Initial N: 16 males
Attrition (final N): 16.

Age

CHO: 22.9±2.6 years
Placebo: 22.5±4.4years.

Other Relevant Demographics

Participated in regular concurrent resistance and endurance training approximately three times per week.

Anthropometrics

Matched for:

Age
Body mass (BM): 80.6±8.8kg vs. 78.2±4.7kg in nutrient vs. placebo
Peak oxygen uptake: 49.8±5.4ml vs. 47.2±6.9ml per kg per minute in nutrient vs. placebo
Strength: One repetition maximum, 1RM; 141.7±4.7kg vs. 141.8±0.8kg in nutrient vs. placebo.

Location

Melbourne, Australia.

Summary of Results:

Findings

Muscle glycogen concentration was higher in the NORM than LOW at all time points in both nutrient and placebo groups (P<0.05)
Post-exercise Akt-p7056K-rpS6 phosphorylation increased in both groups with no differences between legs (P<0.05). mTOR^Ser2448 phosphorylation in placebo increased one hour after exercise in NORM (P<0.05), while mTOR increased approximately four-fold in LOW (P<0.01) and approximately 11-fold in NORM with nutrient (P<0.01; difference between legs P<0.05). Post-exercise rates of myofibrillar protein synthesis (MPS) were not different between NORM and LOW in nutrient or placebo.

Author Conclusion:

Commencing high-intensity resistance exercise with low-muscle glycogen availability does not compromise the anabolic signal and subsequent rates of MPS, at least during the early (four-hour) post-exercise recovery period.

Funding Source:

Not-for-profit

Australian Sports Commission

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?		Yes
	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?	Yes
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)	No
	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.)	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?		N/A
	4.1.	Were follow-up methods described and the same for all groups?	N/A
	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?	N/A
	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?		N/A
	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.)	N/A
	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?	N/A
	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?	N/A
	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