EAL

NAP: Recovery (2014)

Citation:

Tang JE, Manolakos JJ, Kujbida GW, Lysecki PJ, Moore DR, Phillips SM. Minimal whey protein with carbohydrate stimulates muscle protein synthesis following resistance exercise in trained young men. Appl. Physiol. Nutr. Metab. 2007; 32: 1,132-1,138.

PubMed ID: 18059587

Study Design:

Randomized Crossover Trial

Class:

A - Click here for explanation of classification scheme.

Quality Rating:

POSITIVE: See Quality Criteria Checklist below.

Research Purpose:

To determine the impact of post-exercise consumption of a carbohydrate-containing drink with a minimal dose of whey protein (10g total, 4.2g of essential amino acids), vs. a drink containing equal energy as carbohydrate, on resting and post-exercise muscle protein kinetics in resistance-trained young men.

Inclusion Criteria:

Healthy
Actively participating in weight-lifting activities for at least 12 months prior to the study; completing various types of split-body routines, with a minimum of three days per week spent actively lifting weights.

Exclusion Criteria:

Medical condition that would preclude participation in the study (not otherwise described)
Consuming or have consumed in the past eight months any dietary supplements including protein supplements.

Description of Study Protocol:

Recruitment

Posters and advertisements were used to recruit subjects from the McMaster University campus or local Hamilton area.

Design

The study used an all within-subject design, where subjects performed two trials separated by at least two weeks. On each day of the trial, participants received either WHEY or CHO beverage following a unilateral (single-leg) resistance exercise bout, which consisted of four sets of eight to 10 repetitions per set at an intensity equivalent to 80% of the subject's single repetition maximum for both leg extension and leg press exercises. The drink order and exercised leg were determined in a randomized and counter-balanced manner.

Subjects did not perform any leg workouts for four days prior to the trial and rested on the day before testing. Their diets were recorded on the day prior to the first trial and reproduced from trial to trial. Subjects did not consume any food after 9:00 p.m. on the day prior to testing. They reported to the testing center at 6:00 a.m. on trial days.

Blinding Used

Double-blind
Drinks were delievered to the testing facilitiy by the manufacturer
They were identified only as A or B and were identical in color, taste and odor.

Intervention

Post-exercise beverage (both 500kJ): WHEY or CHO
The WHEY drink contained 10g of whey protein isolate and 21g of fructose in 227ml of water
The CHO drink contained 10g of maltodextrin and 21g of fructose in 227ml of water.

Statistical Analysis

Data were analyzed using a two-way repeated-measures ANOVA, with planned comparisons using the paired T-test for post-hoc analysis when significant interaction effects were noted with ANOVA
Significance was accepted as P<0.05.

Data Collection Summary:

Timing of Measurements

A baseline blood sample was taken prior to the subject performing any exercise
Blood samples were drawn throughout the trial
Muscle biopsies were taken from the the exercised (EX) leg and the rested (RE) leg at 180 minutes during the first trial and at 60 minutes and 180 minutes during the second trial.

Dependent Variables

Glucose concentrations (analyzed from whole blood using fluorometric methods previously described)
Plasma insulin (analyzed using a commercially available radioimmunoassay kit)
Amino acid content (analyzed from deproteinized whole blood using high-performance liquid chromatographic methods previously described)
Isotopic enrichment of intramuscular and bound muscle phenylalanine (determined by gas chromatography; mass spectrometry and fractional synthetic rates were calculated using the precursor-product method previously described).

Independent Variables

Post-exercise beverage: WHEY or CHO
The WHEY drink contained 10g of whey protein isolate and 21g of fructose in 227ml of water
The CHO drink contained 10g of maltodextrin and 21g of fructose in 227ml of water.

Control Variables

Timing of measurements
Standardized exercise protocol
Subjects consumed similar diets on the days prior to each trial (all P>0.55)
- WHEY: 153±10kJ per kg, 134±10g protein, 1.44±0.2g per kg protein
- CHO: 150kJ per kg, 139±9g protein, 1.5±0.1g per kg protein.

Description of Actual Data Sample:

Initial N: Eight (eight males, no females)
Attrition (final N): Eight
Age: Mean age, 21±1.0 years
Ethnicity: Not described
Other relevant demographics: Not described
Anthropometrics: BMI, 26.8±0.9kg/m² (mean±SE)
Location: Hamilton, Ontario, Canada.

Summary of Results:

Key Findings

Blood glucose concentrations rose in the CHO trial and were greater than during the WHEY trial at both 30 minutes and 60 minutes post-consumption (P<0.01). Values at 30 minutes and 60 minutes in the CHO trial were also greater than all other times during that trial (P<0.05).
Blood insulin concentration rose in both the WHEY and CHO trials at 30 minutes post-drink (P<0.01), but to a greater extent in the CHO trial, such that insulin concentrations were greater then during the WHEY trial at both 30 minutes and 60 minutes post-drink (P<0.05)
Summed total of branched-chain, essential and total amino acids declined during the CHO trial at 60 minutes post-drink (P<0.05) and persisted throughout the protocol. The WHEY drink induced a rise in amino acids that peaked at 60 minutes post-drink and declined steadily, such that at 180 minutes, post-drink concentrations were not different from pre-drink (P<0.05). Amino acid concentrations were greater at all times after consumption of the WHEY drink than at the same time-points during the CHO trial (P<0.01).
Mixed muscle protein synthesis (MPS) was similar in the rested WHEY and CHO legs (P=0.064). MPS was higher in the exercised WHEY leg than in the rested WHEY leg (P<0.05). MPS was higher in the exercised CHO leg than in the rested CHO leg (P<0.05). The muscle protein fractional synthetic rate (FSR) in the exercised WHEY leg was higher than in the exercised CHO leg (P<0.001). No significant difference was observed between the rested WHEY and rested CHO legs (P=0.064).

Author Conclusion:

When consumed regularly after resistance-training, even a minimal dose of whey protein (10g) and carbohydrate (21g) would be sufficient to support protein accretion.

Funding Source:

Not-for-profit

US National Dairy Council

In-Kind support reported by Industry:

Yes

Reviewer Comments:

Good description of experimental protocol
Technical problems and small biopsy samples did not allow all measurements necessary to calculate rates of muscle protein breakdown (MPB). The authors acknowledge that they may have underestimated the impact of the supplements consumed after exercise by not measuring MPB, although the effect is relatively minor.
The inability to see a difference between resting rates of muscle protein synthesis (MPS) between the rested WHEY and rested CHO legs was likely a type II statistical error. Post-hoc sample size calculations revealed that an additional five subjects would have been required to achieve statistical significance between the rested WHEY and rested CHO MPS estimates. It is also possible that the minimal dose of essential amino acids supplied by the whey protein may not have been enough to sufficiently stimulate MPS at rest, particularly in trained subjects.

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?		Yes
	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?	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?	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?	Yes
	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?	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)?	Yes
	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?	Yes
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