This Academy member benefit temporarily has been made public to allow all practitioners access to content that may assist in patient care during the national pandemic response. Click here for information on joining the Academy. 

Hydration

Hydration and Physical Activity

Citation:

Gonzales-Alonso J, Heaps CL, Coyle EF.  Rehydration after exercise with common beverages and water, Int J Sports Med 1992; 13 (5): 399-406.

PubMed ID: 1521958
 
Study Design:
Non-Randomized Crossover Trial
Class:
C - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:
To determine the effectiveness of 2 popular rehydration beverages: 1) commercially available caffeinated diet coke (Diet Coke) (DC) and 2) a 6% carbohydrate-electrolyte (CE) solution (Gatorade), compared with water regarding whole body rehydration, gastric emptying and the restoration of blood volume during a 2h period of exercise-induced dehydration.
Inclusion Criteria:
Written informed consent; participated in routine exercise; no others mentioned.
Exclusion Criteria:
None mentioned
Description of Study Protocol:

Recruitment Not mentioned

 

Design Within-subects, cross-over design:

Exercise-induced dehydration, 2h rehydration period (4 beverage conditions, W, DC, CE, NF) in thermoneutral environment

 

Blinding used (if applicable) not mentioned

 

Intervention (if applicable) beverage treatments [W, DC, CE, no fluid (NF)]

 

Statistical Analysis

 Comparison among 2 beverages and water, and between CE and W (2-way ANOVA w/repeated measures).

Blood vol and osmolality following ingestion of the 3 drinks were compared w/responses observed when no fluid was ingested.

Sig differences identified using Tukey's post-hoc analysis.  Sig level at p<0.05.

Data Collection Summary:

Timing of Measurements

 Reported to lab 2-3h after standard breakfast; 90 min before lab, drank 500 ml water (ensure euhydration). 

At lab on arrival, voided, sat for 30 min rest, blood samples obtained; body weight taken.

Exercise in environmental chamber, 60-80% VO2max (self-selected) to dehydrate 2.5% loss BW (about 80-100 min).

BW taken; blood samples obtained; began rehydration with beverage treatment - drank 53% fluid lost, immediately.  After 45 min, remaining 47% of rehydration beverage needed to replace 100% fluid lost was consumed.  At end of 2h rehydration period, body weight anduvol obtained.  Questionnaires completed during rehydration re: taste, gastric fullness, pressure. 

Dependent Variables

  • Gastric vol (epigastric impedance)
  • % rehydration (%Body weight lost that was regained)
  • Hgb, Hct
  • sOsm (freezing point method)
  • sElectrolytes (electrolyte analyzer)

Independent Variables

 Beverage: CE, DC, W, NF

Control Variables

 thermoneutral environment (21C, 60%RH) during recovery;

32C, 40%RH during exercise in environmental chamber

Description of Actual Data Sample:

 

Initial N: 10 (sex ?)

Attrition (final N): 16 M, 3 F

Age: 22.8±2.8 yrs

Ethnicity: not mentioned

Other relevant demographics:

Anthropometrics wt:  73.9±12.8 kg; VO2max: 4.2±0.6 l/min

Location: Human performance lab, Univ Texas, Austin, USA

 

Summary of Results:

 

Variables

Diet Cola (DC)

Carb-electrolyte (CE) Water (W)

Control group (NF): no data reported for this group

Statistical Significance of Group Difference

Rehydration% n=10

n=19

 54±5*

not reported

 69±5

73±3

 64±5

65±3*

 

*p<0.05, n=10

p<0.005, n=19

Urine vol (ml) n=10

n=19

 710±100*

not reported

 480±90

340±60

 600±90

500±60*

 

 p<0.05, n=10

p<0.05, n=19

Body wt loss (g) n=10

n=19

 230±20*

 

 110±20

150±20

 140±20

150±20

 

 p<0.05, n=10

ns, n=19

Gastric vol (% of drink remaining in stomach), 15 min after 1st ingestion 54±4 not reported 41±2*   p<0.05, n=6

Urine Electrolyte losses (mEq) during rehydration

Na

K

Cl

 

 

60±12

38±8

97±15

 

 

53±12

41±10

95±16

 

 

78±15

57±14

119±19

  ns (N=10)

 

Other Findings

Similar blood vol responses observed during the 2 studies (n=10, n=19).  At 120 min after CE ingestion, BV sig greater than that of DC, W or NF (p<0.05). 

Ns differences in pre-exercise sOsm among 3 drinks.  After exercise, sOsm elevated equally (292±2 mOsm/kg) above euhydrated state.  Levels returned to euhydrated after drink consumption.  sOsm during 2nd hour of rehydration w/CE remained sig higher vs W (p<0.05).

Similar losses of Na, K, Cl in sweat and urine observed when subjects exercised in heat during all trials.  Ns differences in serum electrolyte concentrations among 3 drinks.  At end of 2h rehydration period, ns differences in any of serum electrolytes. 

DC produced higher subjective ratings of fullness and sensation of gas/pressure 5 min after drinking and the 2nd drink vs CE (P<0.05). 

Author Conclusion:

Ingestion of DC is less effective than water and CE for rehydration during a 2h period following exercise.

Greater rehydration effectiveness follows CE compared with water.

Greater rehydration with CE compared to DC and water is laregly due to less urine formation and greater blood volume restoration probably as a result of its salt and sugar content, which elevates sOsm.

Funding Source:
University/Hospital: University of Texas at Austin
Reviewer Comments:

CE beverages are more effective during a recovery period than DC or water for rehydration due to properties of the beverage (salt and sugar content) which elevate sOsm.   

*Important to see figures for results for visual comparison between treatments*

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
  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
  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
  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
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) Yes
 
Validity Questions
  1. Was the research question clearly stated? Yes
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.1. 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
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? Yes
  1.3. Were the target population and setting specified? Yes
  2. Was the selection of study subjects/patients free from bias? 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
  2.1. 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
  2.2. Were criteria applied equally to all study groups? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? 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
  2.4. Were the subjects/patients a representative sample of the relevant population? Yes
  3. Were study groups comparable? 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
  3.1. 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? ???
  3.2. 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.) 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? 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? Yes
  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.) Yes
  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.) Yes
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? 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. Was method of handling withdrawals described? Yes
  4.1. Were follow-up methods described and the same for all groups? 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
  4.2. 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
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? N/A
  4.4. 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
  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? ???
5. Was blinding used to prevent introduction of bias? ???
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? ???
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? ???
  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.) ???
  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.) ???
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? ???
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? ???
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? 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? ???
  5.5. In diagnostic study, were test results blinded to patient history and other test results? ???
  6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? Yes
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? N/A
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? N/A
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? Yes
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? Yes
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? Yes
  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
  6.4. 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
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? N/A
  6.6. Were extra or unplanned treatments 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? Yes
  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? Yes
  6.8. In diagnostic study, were details of test administration and replication sufficient? Yes
  7. Were outcomes clearly defined and the measurements valid and reliable? Yes
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
  7.1. 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
  7.2. 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
  7.3. 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
  7.4. 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
  7.5. 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
  7.6. Were other factors accounted for (measured) that could affect outcomes? Yes
  7.7. Were the measurements conducted consistently across groups? 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. 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
  8.1. 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
  8.2. 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
  8.3. 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
  8.4. 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)? Yes
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? Yes
  8.6. Was clinical significance as well as statistical significance reported? N/A
  8.6. Was clinical significance as well as statistical significance reported? N/A
  8.7. If negative findings, was a power calculation reported to address type 2 error? N/A
  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. Are conclusions supported by results with biases and limitations taken into consideration? Yes
  9.1. Is there a discussion of findings? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? 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. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes
  10.2. Was the study free from apparent conflict of interest? Yes