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HYD: Assessing Hydration Status (2007)

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

To determine a quick and easy method for assessment of day-to-day hydration status in athletes exercising in the heat

Inclusion Criteria:
  • Part A:
    • (1) Euhydrated control: Healthy but relatively sedentary individuals living in a temperate climate and engaged in their normal activities with no restrictions placed on their diet or activity
    • (2) Hypohydrated group: individuals living in the same temperate climate undertook exercise on a cycle ergometer in a warm (35.2 oC), humid (67%) environment on 7 evenings
  • Part B: Male international class athletes from 3 different sports (gymnastics, boxing, wrestling) during a short period (~11 d) of warm weather training in the southern US (day time temperature high was about 28-24 oC; humidity about 60-90%). 

 

Exclusion Criteria:
No data
Description of Study Protocol:

Recruitment

 No data

Design

 Study of sensitivity and specificity of a diagnostic test (prospective design)

Blinding used (if applicable)

 N/A

Intervention (if applicable)

  • Part A (for hypohydrated group only): Each experimental session separated by about 1 week; a total of 40 min of exercise was undertaken in 10-min bouts separated by 5-min rest periods. Exercise was carried out in the evening, and afterward food, but no drinks. The amount of fluid from food (pizza or chips) is about 150 mL.
  • Part B: Sport competitions - wrestling or boxing by weight category; gymnastics in a training camp

Statistical Analysis

One-way ANOVA

Data Collection Summary:

Timing of Measurements

  • Part A:
    • Euhydrated control: The first urine of the day was collected a short time after rising and before breakfast was consumed on 5 consecutive days.
    • Hypohydrated group: The first urine of the day was collected in the following morning after the evening exercise on 7 consecutive days. This was collected a short time after rising and before breakfast was consumed. At this time, the mean level of dehydration corresponded to a mean (±SD) deficit of 1.85 (±0.38)% of body mass relative to the situation immediately before excercise.
  • Part B: The first urine of the day was collected a short time after rising and before breakfast was consumed on 10 consecutive days. This was collected a short time after rising and before breakfast was consumed or training undertaken.

Dependent Variables

  • Urine osmolality: measured byfreezing point depression (Gonotec Osmomat 030 Cryoscopic Osmometer; Gonotec, Berlin, Germamy), averaged multiple measurements during the study.

Independent Variables

 Dehydration protocols

Control Variables

 None

Description of Actual Data Sample:

 Initial N:

  • Part A (1) euhydrated control: 11 "healthy sedentary individuals"
  • Part A (2) hypohydrated group: 10
  • Part B: 29 male amateur athletes (15 boxing, 6 wrestling, and 8 gymnasticds)

Attrition (final N):

  • Part A (1) euhydrated control: 11 
  • Part A (2) hypohydrated group: 10
  • Part B: 29

Age: No data

Ethnicity: No data

Anthropometrics: No data

Location: Scotland

 

Summary of Results:
I. Mean urine osmolality compared euhydrated controls to hypohydrated individuals living in hot environment

Variables

Euhydrated controls (N=11)

Hypohydrated group (N=10)

P Value of Group Difference

Mean (SE) urine osmolality, osmol.kg-1

 675 (232)

 924 (99)

 <0.0001

II. Mean urine osmolality compared male amateur athletes in weight category sports to those in nonweight category sports training in hot environment

Variables

 Male amateur athletes - weight category (N=21) Male amateur athletes - nonweight category (N=8)

P Value of Group Difference

Mean (SE) urine osmolality, osmol.kg-1

777 (254)

  627 (186)

 <0.0001

 

Author Conclusion:

The osmolality of the first morning urine sample is influenced by hydration status.

Hydration status during competition or training in a warm environment can be effectively monitored by urine analysis.

Funding Source:
University/Hospital: University Medical School (Aberdeen Scottland)
Reviewer Comments:

Part C of the study aimed to look at the relationship between urine osmolality and conductivity as assessed by the Sparta 5 reading. This is not relevant to our question so the data was not extracted here.

Bias and Limitations: The demographic characteristics of participants were unclear. Recruitment and inclusion/exclusion criteria were not reported. The large within person variation was because the subjects were not instructed to follow any particular dietary or drinking regimen and were not making any conscious effort to ensure an adequate fluid intake.

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) N/A
  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? No
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? No
  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? No
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) No
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? No
  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")? ???
4. Was method of handling withdrawals described? Yes
  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%.) 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
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study? Yes
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
  5.2. 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? ???
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
  6.2. 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? N/A
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? 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
  6.7. 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
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)? N/A
  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? 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