Hydration and Physical Activity

Study Design:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:

To compare, under resting conditions, the plasma D2O accumulation profiles of water, and 4 CES differing in percentage (^, 8, 10%) and type (simple sugars, maltodextrins) of carbohydrate. 

Inclusion Criteria:

Healthy, informed consent

Exclusion Criteria:

none mentioned

Description of Study Protocol:

Recruitment not mentioned


Design randomized crossover, 5 beverage conditions, each containig D2O:

water, 6% maltodextrin, 6%, 8%, 10% glucose-fructose

All CES contained 20 mmol/l Na, 3 mmol/l K


Blinding used (if applicable)

 Double-blind, counterbalanced assignment of conditions to subjects.

Intervention (if applicable)

 5 beverage conditions, each containig D2O:

water, 6% maltodextrin, 6%, 8%, 10% glucose-fructose

All CES contained 20 mmol/l Na, 3 mmol/l K


Statistical Analysis

 No statistical analysis section of paper (no analysis plan stated).

Data Collection Summary:

Timing of Measurements

 12 h fast prior to 5 experimental sessions (1 week washout); catheter inserted for blood sampling;

 Ingestion of 275 ml (within 60 sec) of 1 of 5 beverage conditions during rest (sitting quietly).

Blood samples taken before testing, and at 10, 20, 30, 40, 60, 90, 120, 180 min after ingestion.

Dependent Variables

  • D2O accumulation (method not mentioned)
  • Insulin (method not mentioned)
  • glucose (glucose analyzer)

Independent Variables

 5 beverage conditions (275 ml), each containig 20 ml (22.1 g) of 99.8 atom D2O:

water, 6% maltodextrin, 6%, 8%, 10% glucose-fructose

All CES contained 20 mmol/l Na, 3 mmol/l K


Control Variables

 All subjects at rest; amt of beverage ingested; no others mentioned.

Description of Actual Data Sample:


Initial N: N=8 M

Attrition (final N):N=8 M

Age: college-aged (no range or mean±SEM given)

Ethnicity: noty mentioned

Other relevant demographics: none mentioned

Anthropometrics (e.g., were groups same or different on important measures)  None mentioned

Location: Exercise Biochemistry Lab, Dept Exercise Science, school of Public Health, Univ SC, Columbia, SC


Summary of Results:


*No mean±SEM tabular data given - all data in 3 figures*


Other Findings

 Plasma D2O concentration and insulin not significantly different between the 5 drink conditions.

Changes in plasma glucose:  plasma cglu increased after ingestion of the CES, peaking at 20 min for 8% GF, and 30 min for % and 10% GF.  PLasma glu higher with ingestion of CES than water at 20 and 30 min (P<0.05) and returned to baseline (6% M and GF) or below (8%, 10% GF) (P<0.05).  No differences found among the drinks at or after 90 min.

Author Conclusion:

2.5-10% CES beverages, regardlesss if maltodextrin or simple sugars, are not likely to enter the vascular system more slowly than water, and therefore will not compromise fluid replenishment.

Funding Source:
University/Hospital: University of South Carolina
Reviewer Comments:

Conclusions that can be made from this study are limited. 

No statistical plan was described (or P values expected for the sample size, i.e. effect size). 

No subject characteristics/anthrompometrics/demographics described for this small, limited sample. no info re: body weight/ht, activity level, etc

Much information missing from methods (drink temp, subjective feelings, environmental conditions, analysis of plasma measures, hydration status).

Could have done much more with respect to measures obtained.

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) ???
  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? No
  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? No
  2.2. Were criteria applied equally to all study groups? N/A
  2.3. Were health, demographics, and other characteristics of subjects described? No
  2.4. Were the subjects/patients a representative sample of the relevant population? ???
3. Were study groups comparable? ???
  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? ???
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) ???
  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? ???
  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? 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.) 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? No
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? No
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? No
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? ???
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? ???
  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? ???
  6.8. In diagnostic study, were details of test administration and replication sufficient? No
7. Were outcomes clearly defined and the measurements valid and reliable? ???
  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? ???
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? ???
  7.5. Was the measurement of effect at an appropriate level of precision? ???
  7.6. Were other factors accounted for (measured) that could affect outcomes? No
  7.7. Were the measurements conducted consistently across groups? ???
8. Was the statistical analysis appropriate for the study design and type of outcome indicators? ???
  8.1. Were statistical analyses adequately described and the results reported appropriately? No
  8.2. Were correct statistical tests used and assumptions of test not violated? ???
  8.3. Were statistics reported with levels of significance and/or confidence intervals? No
  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? No
  8.7. If negative findings, was a power calculation reported to address type 2 error? No
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? ???
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? No
  10.2. Was the study free from apparent conflict of interest? Yes