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Hydration

HYD: Assessing Hydration Status (2007)

Citation:

Ormerod JK, Elliott TA, Scheett TP, VanHeest JL, Armstrong LE, Maresh CM.  Drinking behavior and perception of thirst in untrained women during 6 weeks of heat acclimation and outdoor training.  Int J Sport Nutrition and Exercise Metabolism 2003; 13: 15-28.

PubMed ID: 12660403
 
Study Design:
Experimental
Class:
C - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:
To characterize drinking behavior of women during a lengthened heat acclimation protocol, without measuring physiological mechanisms.
Inclusion Criteria:
Subjects were to be in good health in past 12 months; free of chronic diseases; lack of any recent changes in menstrual status; no history of eating disorders or depressive illness within past 3 years, appropriate score on Eating Inventory; absence of any contradictions in medical history that might preclude participation (heat-related illness, CVD, chronic respiratory disorder, Htn, metabolic disorder, drug/alcohol dependence); not routinely taking prescription or OTC medicines that would affect variables measured; informed consent
Exclusion Criteria:
None mentioned
Description of Study Protocol:

Recruitment Not mentioned

Design : Exercise heat tolerance (EHT) tests performed at beginning and end of 6-wk training period to ensure acclimation.

Training sessions 6d/wk: 90 min in environmental chamber indoor stair stepping, cycling, tradmill walking; 

Outdoor: running, calisthenics.

Water consumed ad lib; Thirst perception measured during indoor training sessions.

 

Blinding used (if applicable) not mentioned

 

Intervention (if applicable): exercise protocol mentioned above

 

Statistical Analysis: Univariate repeated measures (ANOVA) used to evaluate within-subject differences between weeks 1-6; significance level P<0.05.  T-tests used for post hoc comparisons.  Pearson product-moment correlation to examine correlations between variables throughout weeks 1-6; Alpha set at p<0.05 for all tests.

 

Data Collection Summary:

Timing of Measurements

Indoor days: urine sample upon arrival

Water consumed ad lib; water bottled weighed before and after consumption; time of first drink recorded.

Thirst perception measured at 0, 15, 30, 45, 60, 75, 90 min during indoor training sessions.

Temp, BP, HR recoreded q.15 min during exercise in heat.

Dependent Variables

  • Usg (refractometry)
  • Ucol (color chart)
  • Water intake
  • Thirst perception (thirst sensation scale, 9-point)
  • Rectal temp (thrmistor)
  • Blood pressure
  • Heart rate (polar monitor)

 

Independent Variables

 Exercise training sessions

Heat acclimation

Control Variables

 Environmental chamber conditions and time (90min, 36C, 50-70% RH)

Description of Actual Data Sample:

 

Initial N: 5 untrained females

Attrition (final N):

Age: 23±1

Ethnicity: not mentioned

Other relevant demographics:

Anthropometrics Ht: 161±2 cm; Wt: 65.5±5.3 kg; %BF: 29.2±2.3; VO2max: 36.8±1.6 ml/kg/min

Location: Not mentioned

 

Summary of Results:

 

 

Variables

Pre-heat acclimation

week 1

week 3 week 4 week 6 post-heat acclimation

Statistical Significance of Group Difference

 Usg mean, SE

   1.015±0.004  1.018±0.003  1.013±0.003  1.017±0.003    ns

 Ucol mean, SE

r (w/Usg)

 

2±0.5

0.89*

 3±0.4

0.98*

 2±0.4

0.89*

2±0.4

0.93*

 

 ns

*p<0.05

 water intake (ml)    3310±801  2255±449*  2126±517*  1849±446*    *p<0.05
water intake (# drinks/session)   35±10 22±6* 20±5* 17±5*   *p<0.05
 HR during EHT (bpm)  184±2          154±3  p<0.05
 Temp during EHT (C)  38.8±o.2          38.5±0.2  p<0.05

 

 

Other Findings

 Mean number of drinks consumed during week 6 sig lower than weeks 3 and 4 (P<0.05).  Average volume per drink tended to decrease from week 1 to week 6 (ns).  Mean time tot ake a drink increased progressively from week 1 (9.9±2 min) to week 6 (23.1±4.7 min) (p<0.05).

THirst ratings ns between weeks 1 and 6 at 15, 30, 45 min.  At 60 min, ratings began to sig decrease (P<0.05) from week 1 (5±0.4) to week 6 (4±0.4).  This decrease also evident at 75 min; ns at 90 min, though there was a trend toward progressive decrease from week 1-6.

Correlational analyses: 

Avg number of drinks weeks 4-6 and thirst ratings at 30, 45, 60, 75 min (p<0.05).

Avg thirst ratings and avg volume/drink ns.

Usg sig correlated with Ucol, weeks 1-6 (p<0.05).

Author Conclusion:

 

A lengthly acclimation protocol resulted in Women decreasing their total  mean water intake as heat acclimation progressed, which resulted from 1) a decrease in the number of drinks, 2) greater time to first drink, and 3) a decrease in the total volume ingested each week. 

Thirst ratings were relatively low throughout the study - perception of thirst in this study does not appear to be a suffucuent stimulus for maintaining fluid ingestion under stressors such as eercise, heat, and dehydration.

Funding Source:
University/Hospital: Florida State University, Shriner's Burn Hospital, University of Southern Mississisippi, University of Connecticut
Reviewer Comments:

Usg and Ucol did not change during the protocol; Total water intake depends on several factors, including: number of drinks, time to drink, and total volume ingested.

See Figures 1 and 2 for heat acclimation's effects on fluid ingestion and thirst ratings. 

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? ???
  2.4. Were the subjects/patients a representative sample of the relevant population? ???
  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) N/A
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) N/A
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? 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
  3.3. 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.) 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")? ???
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? ???
  4. Was method of handling withdrawals described? 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
  4.1. 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? N/A
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? N/A
  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
  5.2. 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? ???
  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? 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? 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? ???
  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? ???
  7.6. Were other factors accounted for (measured) that could affect outcomes? ???
  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)? No
  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? ???
  8.6. Was clinical significance as well as statistical significance reported? ???
  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