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Hydration

Hydration and Physical Activity

Citation:

Stachenfeld NS, Gleim GW, Zabetakis PM, Nicholas JA.   Fluid balance and renal response following dehydrating exercise in well-trained men and women.   Eur J Appl Physiol 1996; 72: 468-77.

PubMed ID: 8925818
 
Study Design:
Experimental: observational
Class:
C - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:

To document the recovery of plasma volume, plasma osmolality, fluid-regulating hormones and renal function during the period following dehydrating exercise in well-trained women and men. 

Hyp: following dehydrating exercise, renal water and Na retention would be greater in women despite lower or comparable concentrations of fluid-regulating hormones. 

Inclusion Criteria:

M & F:well-conditioned, cyclists & bi-athletes, no medical problems, taking no medications; informed consent

F: consistent normal menstrual cycle

Exclusion Criteria:
None mentioned
Description of Study Protocol:

Recruitment Not mentioned

 

Design Experimental trial, observational

 

Blinding used (if applicable) n/a

 

Intervention (if applicable) n/a

 

Statistical Analysis

Recovery responses to dehydration challenge compared using 2-way ANOVA for repeated measures; Sex used as covariate (ANCOVA);  Sig level of p<0.05.

Data Collection Summary:

Timing of Measurements

Pre-test:  assessment of VO2max, VT; ingestion of NaCl 2d prior to dehydration to ensure Na balance: 24h urine collected and Na balance determined; body weight taken.

Dehydration test: came to lab in euhydrated state; urine collected; catheter for saline administration inserted; blood samples taken, HR monitored, blood pressure measured; Exercised on cycle for 25 min periods with 5 min rests (weights obtained) in between until loss of 3% BW. 

Recovery: After 3% loss reached, cooled down on bike for 15 min, blood sample taken, urine collected.  consumed amt of water to match 1% initial body mass within first 30 min of recovery.  blood sampled at 30, 60, 120, 240 min; urine collected at 60, 120, 240  min.  HR and BP recorded q. 60 min.

Dependent Variables

  • Fluid balance (plasma vol, Osm, Na, K)
  • Renal function (glomerular filtration rate (GFR), Urine vol (Uv), Osm clearance (Cosm), Water clearance (Cwater), Urine Na-volume (Una-v), Urine potassium (Uk-v), Uosm/Osm-pl)
  • Hormone levels (AVP, Aldosterone (ALDO), Norepinephrine (NE), PRA)

 

Independent Variables

 Exposure to heat and exercise

Control Variables

 Controlled temp during exercise (32C, <40% RH) and recovery; exercise workloads (60% VO2max)

Description of Actual Data Sample:

 

Initial N: 10M, 8F

Attrition (final N): 18: 10 M, 8 F

Age: See table below for subject characteristics

Ethnicity: not mentioned

Other relevant demographics: well-trained athletes.

Anthropometrics (e.g., were groups same or different on important measures)

  M = 10 F = 8
Age, yr 28.6±1.6 31.1±1.5
Weight, kg 72.0±2.6* 60.2±1.8
ht, cm 178.5±1.9* 166.3±1.4
Body fat, % 10.8±0.8* 14.7±2.6
VO2peak, l/min 4.682±0.191* 3.521±0.157
VO2peak, ml/kg/min 65.0±1.7* 58.7±2.3
VO2peak, ml/kg/FFM/min 74.0±1.5 68.5±2.3
VO2 at VT, ml/kg/min 39.3±1.5 36.8±2.8
%VO2peak at VT, % 60.4±1.6 63.1±1.7
Time to lose 3% BW, min 129.6±14.3 121.3±10.0
End exercise VO2, ml/kg/min 35.75±1.72 34.82±1.38
End exercise HR, bpm 164±3 156±4

*P<0.05, M vs F

Location: Lab, Nicholas Inst of Sports Med and Athletic Trauma & Nephrology Section, Lenox Hill Hospital, NY, USA

 

Summary of Results:

 

 

Variables

Baseline

End exercise

Recovery,

30 min

Recovery,

60 min

Recovery,

120 min

Recovery,

240 min

Statistical Significance of Group Difference

[Na], mmol/l

M, F

 138.7±0.7, 138.8±0.7

 141.4±0.7, 143.7±0.7

 140.4±1.0, 140.4±1.0 138.1±0.9, 140.4±1.3  139.2±0.9, 139.4±0.5  139.0±0.07, 140.0±0.7 

 M vs F ns

[K], mmol/l

M, F

 4.11±0.09, 4.05±0.09

 4.86±0.09, 5.03±0.08

 4.35±0.08, 4.39±0.08  4.41±0.06, 4.33±0.13  4.33±0.07*, 4.14±0.07  4.17±0.06*, 4.06±0.07

 *p=0.08 M vs F

GFR, ml/min

M, F

 123.8±21.5, 125.5±14.1

68.8±14.3, 84.7±18.7 

--  --  119.9±18.7, 118.1±26.9  136.8±22.6, 151.2±10.8 

ns 

Urine v, ml/l

M, F

 2.74±0.71, 3.27±0.93 0.86±0.35, 0.76±0.23*  --  --  1.12±0.28, 0.41±0.07* 

0.62±0.10*, 0.99±0.17 

 *p<0.05 from baseline

Cosm, ml/l

M, F

 2.90±0.40, 2.02±0.52 1.18±0.23, 1.15±0.37  --  --  2.62±0.40**, 1.25±0.23  1.66±0.34**, 3.13±0.55   **M vs F

Cwater, ml/l

M, F

-0.11±0.53, 1.32±0.70  -0.21±0.32,   -0.39±0.25  --   -- -1.39±0.26,     -0.86±0.25  -1.03±0.21* , -2.18±0.37** 

 *p<0.05 from baseline

** Mvs F

U Na v, mmol/l

M, F

 11.3±2.5, 9.2±3.2 4.3±2.6, 3.0±1.3  --  --  7.6±0.8, 3.6±1.7  10.3±2.5, 13.5±3.3   ns

UK v, mmol/l

M, F

 4.8±1.1, 5.9±1.5 5.4±1.4, 6.1±1.6  --  --  8.4±1.4. 6.7±2.1  6.9±1.2**, 14.5±3.2   **M vs F

Uosm/Osm-pl

M, F

 1.17±0.19, 0.84±0.27 1.58±0.31, 1.59±0.21  --  - - 2.61±0.23*, 2.83±0.22*  3.04±0.15*, 3.13±0.36*   *p<0.05 from baseline

 

 

Other Findings

No sig baseline differences between M and F in Osm-u, pl, Na, K, PRA, ALD, NE, Uv, Cosm, Cwater, Una-V, Uk-v; AVP sig lower in F. 

Dehydration and exercise: %PV change of -10.19±0.96 and -12.21±0.96 for M and F; Osm-pl increased sig to 295±1.38 and 296±0.86 mosmol/kg water in M and F. 

Hormones: Exercise resulted in sig incr in AVP, ALDO, PRA, and NE in M and F.  At end of exercise, M had sig higher PRA than F; NE 30% higher in men. 

Author Conclusion:

Following exercise-induced dehydration, well-trained men and women had similar responses for early (<120 min) recovery. 

Women had a sig greater rate of water reabsorption during last 120 min of a 240 min recovery period.  Women also had slight [AVP]pl elevations relative to baseline throughout recovery, which may in part explain their greater water reabsoprtion.  Women also had a more rapid recovery of [ALDO]s which was consistent with lower Na reabsorption. 

The sex differences in renal fluid and Na regulatory function may have been due to estrogen effects on fluid-regulating hormones and water retention.  Despite these small differences, overall fluid balance during exercise and recovery were similar between men and women. 

 

Funding Source:
University/Hospital: nicholas institute of sports medicine and athletic trauma
Reviewer Comments:
See paper for time-course figures:Osm, plasma vol, hormones, clearances*
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) 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.) 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? 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? N/A
5. Was blinding used to prevent introduction of bias? N/A
  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? 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
  5.4. 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
  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? 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? ???
  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