EAL

NAP: Training (2014)

Citation:

Morton JP, Croft L, Bartlett JD, MacLaren DPM, Reilly T, Evans L, McArdle A, Drust B. Reduced carbohydrate availability does not modulate training-induced heat shock protein adaptations but does upregulate oxidative enzyme activity in human skeletal muscle. J Appl Physiol. 2009; 106: 1,513-1,521.

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 test the hypothesis that training with reduced carbohydrate availability from both endogenous and exogenous sources provides an enhanced stimulus for training-induced heat shock protein (HSP) adaptations of skeletal muscle
To investigate the influence of reduced carbohydrate availability on oxidative adaptations and exercise performance.

Inclusion Criteria:

Recreationally active men.

Exclusion Criteria:

History of neurological disease or musculoskeletal abnormality
Pharmacological treatment.

Description of Study Protocol:

Design

RCT study.

Intervention

Six weeks of high-intensity intermittent running: Group One (Low + Glu) and Group Two (Low + Pla) trained twice per day, two days per week and consumed a 6.4% glucose or placebo solution, respectively, immediately before every second training session and at regular intervals throughout exercise. Group Three (Norm) trained once per day, four days per week and drank no beverage throughout training.

Statistical Analysis

Two-way mixed-design repeated-measures general linear model where the within factor was time (pre-training vs. post-training) and the between factor was training condition. Changes in the metabolic cost of the criterion exercise session were assessed using a three-way mixed-design repeated-measures general linear model where the within factors were acute exercise response and training status and between factor was training condition. Where there was a significant interaction effect, Bonferroni post-hoc tests were used to locate differences.

Data Collection Summary:

Timing of Measurements
Pre- and post-exercise at criterion exercise after pre-training test and again after six weeks of training and diet.

Dependent Variables

Muscle glycogen concentration, muscle HSP0, HSP60, HSP27, aß-cryatallin, Mn superoxide dismutase (MnSOD), cytochrome-c oxidase IV (COXIV), peroxisome proliferator-activated receptor-„y(GC1-a) and succinate dehydrogenase (SDH) activity coactivator 1-: Muscle biopsy of vastus lateralis and gastrocnemius
Plasma glucose, lactate, nonesterified fatty acid (NEFA), glycerol, and serum insulin: Blood draw.

Independent Variables

Six weeks of high-intensity intermittent running:

Group One (Low + Glu): Trained twice per day, two days per week and consumed 6.4% glucose immediately before every second training session and at regular intervals throughout the exercise
Group Two (Low + Pla): Trained twice per day, two days per week and consumed a placebo solution immediately before every second training session and at regular intervals throughout exercise
Group Three (Norm): Trained once per day, four days per week and drank no beverage throughout training.

Control Variables

Six weeks of high-intensity intermittent running four times per week after a initial assessment of maximal oxygen uptake and Yo-Yo Intermittent Recovery test.

Description of Actual Data Sample:

Initial N

30 males.

Attrition (Final N):

A total of 23 subjects:

Low + Glu: Eight
Low + Pla: Seven
Norm: Eight.

Age

Low + Glu: 20±1 years
Low + Pla: 21±1 years
Norm: 20±1 years.

Anthropometrics

Body mass (BM):

Low + Glu: 79±7.5
Low + Pla: 74.5±7.8
Norm: 77±10.7.

Location

Liverpool, UK.

Summary of Results:

Findings

Training improved all performance parameters in all groups (P=0.001 for all indexes) with no difference between training conditions
No difference between groups in the magnitude of the training induced increase in muscle proteins (HSP70, HSP60, aB-crystallin, MnSOD, and PGC1-a) except for HSP27, which showed no change in either muscle
Training increased SDH activity in both muscles (P=0.001) in all groups. Training induced increases in SDH activity were significantly larger (P=0.03 for gastrocnemius and P=0.04 for vastus lateralis) for Low + Pla compared to other conditions
Training reduced glycogen utilization in the gastrocnemius muscle (P=0.04) during the criterion exercise although there was no difference between groups. Training did not affect glycogen utilization in the vastus lateralis muscle. Resting muscle glycogen concentration showed no significant change in either muscle for any group.
Acute exercise increased plasma glucose (P=0.03), lactate (P=0.001), NEFA (P=0.001) and glycerol (P=0.001), and decreased serum insulin (0.002) in both untrained and trained state. Only lactate changed with training (P=0.001) with values being lower. There was no difference between groups for any blood metabolite.

Author Conclusion:

In whole body exercise conditions, carbohydrate availability appears to have no modulating effect on training-induced increases of the HSP content of skeletal muscle. In contrast, training under conditions of reduced carbohydrate availability from both endogenous and exogenous sources provides an enhance stimulus for inducing oxidative enzyme adaptations of skeletal muscle although this does not translate to improved performance during high-intensity exercise.

Funding Source:

Industry:

GlaxoSmithKline Nutritional Health Care (UK)

Pharmaceutical/Dietary Supplement Company:

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)	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?		N/A
	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%.)	No
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	Yes
	4.4.	Were reasons for withdrawals similar across groups?	???
	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?	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?	N/A
	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?	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