EAL

Hydration and Physical Activity

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To assess the involuntary dehydration phenomenon in humans: to examine distribution and fate of water ingested during rehydration to determine the mechanisms contributing to the high retention of ingested fluids in the vascular space.

Inclusion Criteria:

None mentioned

Exclusion Criteria:

None mentioned

Description of Study Protocol:

Recruitment Not mentioned

Design Experimental: trial w/concurrent controls

Blinding used (if applicable) Not mentioned

Intervention (if applicable) 2 series of rehydration experiments on each subject: 1) tap water & 2) 0.45% NaCl solution

Statistical Analysis 2-way ANOVA for repeated measures to determine differences between tap water and NaCl solution, sig differences determined by Tukey's minimum sig difference test; Specific trend analysis for each treatment by 1-way ANOVA for repeated measures and Tukey's MSD test; Sig level of p<0.05. Regression formulas calculated by Brace's method.

Data Collection Summary:

Timing of Measurements

Exercise-induced dehydration: 2.3% body wt loss: 90-110 min to exercise at 40% VO2 max in 36C, <30%RH

Recovery, 60 min: no fluid, 28C, <30%RH, seated; blood samples taken at 30 and 60 min

Rehydration, 180 min: water plus capsules(0.2 mg sucrose/100ml water sucrose in tap condition, 0.45g NaCl/100 ml water in NaCl condition) ad lib. Tap water vs 0.45% NaCl solution. Water temp of 15C; drink at least 100ml at a time (1 capsule/100ml). blood samples taken at 10, 20, 30 60, 120, 180 min; urine collected at 60, 120, 180 min.

Dependent Variables

Na and K (flame photometry); Cl (Cotlove chloride titrator)
pOsm (freezing point depression)
Hct, hgb (cyanomethemoglobin)
Plasma protein (refractometry)
plasma solid concentration (dry weight method)

Independent Variables

Solution consumed during rehydration (tap vs NaCl)

Control Variables

Drink temp; temps during exercise and recovery

Description of Actual Data Sample:

Initial N: 6M

Attrition (final N): 6M

Age: See table below for subject characteristics.

Ethnicity: Not mentioned

Other relevant demographics: None mentioned

Anthropometrics

	Age, yr	Wt, kg	VO2max, ml/kg/min	Blood vol, ml/kg	Plasma vol, ml/kg
Mean	28.3	68.3	51.8	82.1	47.4
range	23- 33	56.5-83.7	36.4- 62.9	61-102.3	33.5-61.4

Location: JB Pierce Foundation Lab, Depts of Epidemiology and Public Health and Physiology, Yale Univ, CT, USA

Summary of Results:

Variables	Dehydration	Rehydration	Rehydration 60 min	Rehydration 120 min	Rehydration 180 min	Statistical Significance of Group Difference
Urine flow, uL/kg/min Tap, NaCl	9.7±1.6, 9.0±1.2	--	8.9±0.9, 8.4±1.3	21.0±11.4, 11.5±2.8	25.9±17.2, 12.1±3.5	--
Net fluid gain, ml/kg bw	--	--	--	12.1±1.6	15.3±2.4	p<0.05
uOsmol*urine flow, uosmol Tap, NaCl	7.9±0.9, 7.5±0.5	--	8.6±0.9, 7.5±0.5	8.2±1.0, 9.3±1.3	7.1±0.7, 9.3±1.0*	*p<0.05
Cosmol, uL/kg/min Tap, NaCl	27.5±3.0, 25.9±1.7	--	29.9±3.2, 26.1±1.8	28.7±3.5, 32.4±4.4	25.3±2.6, 33.9±3.0*	*p<0.05
Cwater, uL/kg/min Tap, NaCl	-17.8±2.2, -16.9±2.2	--	-21.0±2.4, -17.7±1.3	-7.7±11.1, -21.0±4.2*	0.6±16.2, -21.7±3.8*	*p<0.05
total body water deficit before rehydration, ml/kg bw Tap, NaCl	23.7±0.9, 21.7±1.0	--	--	--	--	ns
Na loss, mEq/kg BW Tap, NaCl	-1.01±0.15, -1.18±0.12	-1.28±0.17, -1.48±0.13*	--	--	--	*p<0.05
K loss, mEq/kg Tap, NaCl	-0.31±0.03, -0.31±0.03	-0.54±0.05, 0.58±0.03*	--	--	--	*p<0.05
Cl loss, mEq/kg Tap, NaCl	-0.95±0.11, -1.09±0.14	-1.28±0.12, -1.53±0.16*	--	--	--	*p<0.05
Na intake	--	na, +1.40±0.22	--	--	--
Cation balance, mEq/kg bw Tap, NaCl	-1.32±0.15, -1.49±0.13	-1.81±0.17, -0.66±0.14*	--	--	--	*p<0.05
Total pro content, g/kg Tap, NaCl	3.4±0.2 (both groups)	3.4±0.3, 3.5±0.2	--	--	--	--
PLasma vol deficit, ml/kg bw Tap, NaCl	2.28±0.51, 2.14±0.6	--	--	--	-0.51±0.8, +1.58±0.63	p not reported

Other Findings

Author Conclusion:

During recovery from moderate (2.3% body weight) whole-body dehydration, a delay in rehydration is caused by both the electrolyte deficit from the intracellular and extracellular spaces and the removal of a vol-dependent dipsogenic drive due to the selective retention of ingested fluid in vascular space.

Funding Source:

Government:

NHLBI

Reviewer Comments:

See figures for time-course data; very small sample, not great description of subject population (i.e. physical activity level, %BF).

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?	???
2.	Was the selection of study subjects/patients free from bias?		???
	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
	2.1.	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
	2.2.	Were criteria applied equally to all study groups?	N/A
	2.3.	Were health, demographics, and other characteristics of subjects described?	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?	???
	2.4.	Were the subjects/patients a representative sample of the relevant population?	???
	3.	Were study groups comparable?	N/A
3.	Were study groups comparable?		N/A
	3.1.	Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT)	N/A
	3.1.	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?	???
	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?	???
	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
	3.5.	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
	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.	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?	???
	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.)	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?	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?	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?	???
	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