EAL

NAP: Training (2014)

Citation:

Kern M, Heslin CJ, Rezende RS. Metabolic and Performance Effects of Raisins Versus Sports Gel as Pre-Exercise Feedings in Cyclists. Journal of Strength and Conditioning Research, 2007, 21 (4): 1,204-1,207.

PubMed ID: 18076252

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 assess differences in metabolism and cycling performance after consumption of a lower (raisins) vs. a higher (commercial sports gel) GI food.

Inclusion Criteria:

12 in-season endurance-trained cyclists were recruited

Including triathletes and duathletes
Between 18 years and 40 years of age
Cycling at least 150 miles per week.

Exclusion Criteria:

Metabolic disorders
Smoking
Pregnancy.

Description of Study Protocol:

Recruitment

12 cyclists recruited. No further information provided.

Design

Subjects were fed isoenergetic amounts of the high- or low-GI foods 45 minutes prior to the subjects completing a constant-intensity 45-minute exercise bout followed by a 15-minute performance ride using a randomized, balanced cross-over design.

Subjects reported to the laboratory in a (12-hour) fasted state, having abstained from alcohol, tobacco, caffeine and strenuous exercise for the previous 24 hours
Subjects consumed raisins (California, red) prior to exercise on one occasion and a commercial sports gel (Clif Shot, vanilla, Berkeley, CA) prior to the other
Trials were separated by at least seven days and subjects were instructed to continue their normal diet habits during the days separating trials
One gram of carbohydrate per kilogram body weight from either raisins or sports gel was fed and subjects rested in a seated position for 45 minutes
Blood was collected from an antecubital vein at the end of the resting period in tubes containing clot activator and gel separator for serum, as well as tubes containing ethylenediaminetetraacetic acid (EDTA) for whole blood
After the resting period, subjects warmed up on a cycle ergometer for three minutes at 100W, then cycled for 45 minutes at 70% of VO_2max
After the 45th minute, a second blood sample was collected and subjects began a 15-minute performance trial with the cycle ergometer set in ‘‘linear’’ mode to determine total accumulated work.

Blinding Used

Sunjects were blinded from knowledge of work output.

Intervention

Subjects were fed one gram carbohydrate per kilogram body weight from either raisins or sports gel 45 minutes prior to exercise.

Subjects consumed raisins (California, red) prior to exercise on one occasion and a commercial sports gel (Clif Shot, vanilla, Berkeley, CA) prior to the other
One gram of carbohydrate per kilogram body weight from either raisins or sports gel was fed and subjects rested in a seated position for 45 minutes.

Statistical Analysis

Statistical analyses were conducted using the Statistical Program for the Social Sciences computer software package
Data are presented as means ±SD
A paired-comparisons T-test was used to analyze the difference in performance between the trials
Repeated measures analysis of variance (two trials, two time-points) tests were used to analyze differences in biochemical variables
Paired comparisons T-tests were used as post-hoc tests where necessary
An alpha level of P<0.05 was considered statistically significant.

Data Collection Summary:

Timing of Measurements

Blood was collected prior to excercise bout as well as after the 45th minute.

Dependent Variables

Blood levels of glucose, insulin, lactate, FFA's, beta-hydroxybutyrate, triglycerides
Exercise performance.

Independent Variables

Sports gel and raisin consumption.

Description of Actual Data Sample:

Initial N
12

Attrition (Final N)
Eight (four males, four females).

Age

Males: 30.2±2.3 years
Females: 29.2±5.8 years.

Ethnicity

Not stated.

Other Relevant Demographics

None stated.

Anthropometrics

Weight: Men, 75.5±5.8kg; women, 56.22±5.2kg
VO_2max: Men, 64.1±3.4; women, 47.5±10.6.

Location
San Diego State University.

Summary of Results:

Key Findings

Serum glucose, blood lactate, TG, and FFA concentrations were similar between trials.

Insulin and Fuel Substrate Concentrations Before and After Exercise

Variables	Raisin Group		Sports Gel		Significant Main Effect of Exercise
Variables	Pre-exercise (mean±SD)	Post-exercise (mean±SD)	Pre-exercise (mean±SD)	Post-exercise (mean±SD)	Significant Main Effect of Exercise
Insulin (U·ml1)	61.4±37.4	13.3±18.9	110±70.4	14.2±6.2	P<0.05
Glucose (mmol·L1)	7.15±1.80	6.19±1.57	6.87±1.29	5.73±0.94	P<0.05
Lactate (mmol·L1)	1.79±0.32	2.32±1.15	1.39±0.29	2.49±1.51	P<0.05
Free fatty acids (mmol·L1)	0.29±0.08	0.49±0.15	0.26±0.09	0.36±0.16	P<0.05
Triglycerides (mmol·L1)	0.95±0.35	1.02±0.41	0.85±0.34	0.86±0.37	P<0.05
Beta-hydroxybutyrate (mmol·L1)	0.07±0.02	0.08±0.04	0.06±0.02	0.08±0.02	P<0.05

Author Conclusion:

It may be concluded from this study that, despite their differences in GI, raisins and a commercial sports gel fed in the amount of one gram of carbohydrate per kilogram of body weight 45 minutes prior to cycling elicit relatively similar metabolic effects after 45 minutes of exercise and an equal work output during a subsequent 15-minute performance trial.

Funding Source:

Industry:

California Raisin Marketing Board

Food Company:

Reviewer Comments:

No statement of how recruitment was accomplished, ethnicity or why people dropped out
Very small sample size
No consideration of metabolic differences for varying GI foods with the addition of a protein or fat, except to say that future research can be done on this.

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?	???
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?	???
	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?	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?	???
	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?	No
	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)?	No
	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?		???
	10.1.	Were sources of funding and investigators' affiliations described?	Yes
	10.2.	Was the study free from apparent conflict of interest?	???