Hydration and Physical Activity
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.
M & F:well-conditioned, cyclists & bi-athletes, no medical problems, taking no medications; informed consent
F: consistent normal menstrual cycle
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.
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)
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
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.
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.
University/Hospital: | nicholas institute of sports medicine and athletic trauma |
Quality Criteria Checklist: Primary Research
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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 | |