NAP: Training (2014)

Citation:

Havemann L, West SJ, Goedecke JH, Macdonald IA, St Clair Gibson A, Noakes TD, Lambert EV. Fat adaptation followed by carbohydrate loading compromises high-intensity sprint performance. J Appl Physiol. 2006; 100: 194-202.

 
Study Design:
Randomized Controlled Trial
Class:
A - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:
To investigate the the effect of a high-fat diet (HFD) followed by one day of carbohydrate (CHO) loading on substrate utilization, heart rate variability (HRV), effort perception [rating or perceived exertion (RPE)], muscle recruitment [electromyograph (EMG)] and performance during a 100km cycling time trial.
Inclusion Criteria:
Endurance-trained male cyclist.
Exclusion Criteria:
  • Metabolic condition
  • Taking medication for chronic condition.
Description of Study Protocol:

Design

Single blind, crossover study.

Blinding Used 

Subjects to the diet by covertly manipulating the macronutrient composition.

Intervention 

HFD (68% energy from fat) for six days followed by one day of CHO loading (90% energy from CHO) or equal-energy CHO diet  (68% energy from CHO) for six days followed by one day of CHO loading (90% energy from CHO). 

Statistical Analysis

ANOVA with repeated measures and the Tukey post-hoc analysis.

Data Collection Summary:

Timing of Measurements

Resting HRV and resting and exercising RER were tested on days one, three, five and seven. Bloods and EMG were tested on days seven and eight.

Dependent Variables

  • Blood glucose, insulin, lactate, epinephrine, norepinephrine, catecholamine, FFA
  • Muscle recruitment patterns: EMG
  • HRV: Heart rate monitor
  • RER: Online computerized system
  • Rate of perceived exertion (RPE): Borg six to 20 RPE scale.

Independent Variables

HFD (68% energy from fat) for six days followed by a one-day CHO loading (90% energy from CHO) or equal-energy CHO diet (68% energy from CHO) for six days followed by one day of CHO loading (90% energy from CHO). All meals were formulated by an RDN and were pre-packed and provided for the subjects with a diary to record any deviations. Diets were blinded by overtly manipulating the macronutrient compositions.

Control Variables

A 100km time trial (TT) on day one and day eight. A 60-minute steady-state (SS) cycle at 63% of peak power output on days three, five and seven. 

Description of Actual Data Sample:
  • Initial N: Eight males
  • Attrition (final N): Eight
  • Age: 26.0±3.3 years (range 22.0 to 32.0 years).

Other relevant demographics

  • VO2peak: 57.8±5.5ml per kg per minute
  • Wpeak: 361±36W.

Anthropometrics 

  • BM: 81.3±9.6kg
  • Height: 1.8±0.1m
  • BF: 14.0±2.8%.

Location

Cape Town, South Africa.

Summary of Results:

Findings

  • Ingestion of the HFD reduced RER at (P<0.005) and during exercise (P<0.01) and increased plasma free fatty acid levels (P<0.01), indicating increased fat utilization. There was a tendency for the low-frequency power component of HRV to be greater for HFD-CHO (P=0.056), suggestive of increased sympathetic activation. 
  • Overall 100km time-trial performance was not different between diets; however, 1km sprint power output after HFD-CHO was lower (P<0.05), compared with HCD-CHO. Despite a reduced power output with HFD-CHO, RPE, heart rate and EMG were not different between trials. 

 

Author Conclusion:
HFD-CHO dietary strategy increased fat oxidation, but compromised high-intensity sprint performance.
Funding Source:
Industry:
Bromor Foods Pty Ltd, Technology and Human Resources for Industry Programme
Food Company:
University/Hospital: University of Cape Town
Not-for-profit
National Research Foundation
Other: Medical Research Council of South Africa
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? 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? 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.) 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