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Hydration

Hydration and Physical Activity

Citation:

McConell, GK., Stephens, TJ., and Canny, BJ.  Fluid Ingestion does not influence intense 1-h exercise performance in a mild environment.  Med Sci Sports Exer. 1999;31(3):386-392.

PubMed ID: 10188742
 
Study Design:
Non-Randomized Crossover Trial
Class:
C - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:
To examine the role of ingested fluid volume (no fluid, amount that prevented body mass loss, and 50% of amount needed to prevent body mass loss) on physiological responses and performance during 1 hour of intense exercise conducted at 21 C in trained men.
Inclusion Criteria:

Not provided

Description of the subjects:  Male, well trained cyclist/triathletes

Exclusion Criteria:

Not provided

Description of Study Protocol:

Recruitment  No recruitment, men volunteered for the study

 

Design  Crossover design.  The order of the trials was counterbalanced, then the particular combination of trials was randomly assigned to each subject

 

Blinding used (if applicable)

 

Intervention (if applicable)

Subjects exercised on a cycle ergometer for 45 minutes at a workload that elicited 80 + 1% VO2peak, followed immediately by a 15-min "all out" performance ride.  The trial took place in an air-conditioned lab with a mean wet dry bulb temperature of 20.9 + 0.2 °C and a relative humidity of 41 + 2%.  During the trial subjects received either:  no fluid (NF), fluid (water at room temperature) equivalent to either 100% (FR-100) or 50% (FR-50) of the body mass loss incurred during the familiarization trial.  The fluid was divided into 4 equal portions and ingested immediately before commencing exercise and then at 15, 30 and 43 min of exercise

Statistical Analysis

 2-way (treatment and time) ANOVA  with repeated measures.  If significant differences were found, the location was determined using a Fisher's least significant different test.   One-way ANOVA was used where appropriate.  Level of significance was P < 0.05.

Data Collection Summary:

Timing of Measurements

  • Heart rate (HR) was measured at 5,10, 20, 30, 40,45,50,55 and 60 min
  • Oxygen consumption (VO2) was measured at 10 and 40 min of exercise
  • Rating of perceived exertion (RPE) was measured using the Borg Scale (14 pt)
  • Rating of stomach fullness was measured using a 5 pt scale (1= no bloating to 5=severe stomach bloating/fullness).
  • Venous blood sample (glucose, lactate, sodium, potassium) collected at rest and after 10, 30, 45 and 60 min of exercise.
  • Blood sample (hemoglobin and hematocrit), collected at rest and after 10, 30, and 60 min of exercise.
  • Body weight: nude weight before exercise and immediately following the 60 min exercise trial.
  • Urine sample collected and measured immediately following 60 min exercise trial.
  • Sweat loss:  body mass loss corrected for ingested fluid volume, any urine excreted during the actual trial, and estimated metabolic and respiratory losses.

Dependent Variables

  • HR
  • Peak Workload 
  • Rectal temperature
  • RPE
  • Stomach fullness ratings
  • Plasma volume, glucose, sodium, lactate, potassium
  • Sweat rate

Independent Variables

  • No fluid (NF)
  • Fluid (water at room temperature) equivalent to 100% (FR-100) of the body mass loss incurred during the familiarization trial. 
  • Fluid (water at room temperature) equivalent to 50% (FR-50) of the body mass loss incurred during the familiarization trial. 

Control Variables

Pre trial hydration status:  subjects were instructed to drink fluid to produce "clear"urine in the 24 h preceding the trial; 2 h before reporting to the lab on the day of the trial subjects were instructed to drink  3.5 mL//kg BM of water.

Subjects were asked to refrain from physical exercise, alcohol and caffeine on the day before each trial.  Subjects completed a food record of all foods and fluids consumed on the day before trial 1 and were asked to duplicate this meal plan on the day before the following 2 trials.  There was no mention, however, if this was actually done or what the compliance rate was to this test protocol. 

Description of Actual Data Sample:

 

Initial N: 8 subjects volunteered (started and completed study)

Attrition (final N): 8

On Fig 1 Rectal Temperature N=7, there is no explanation for why 1 subject's data is not included.

Age: 26+1 year

Ethnicity:

Other relevant demographics:

Anthropometrics Height:  183+ 2 cm; Body mass 79.6+ 3.5 kg

Location: Monash University, Australia

 

Summary of Results:

Variables

NF

Measures and standard deviation

FR-50

Measures and standard deviation

FR-100

Measures and standard deviation

Volume Fluid Ingested (L)

-

0.72 + 0.03*

1.47 + 0.06*^

Body Mass Loss (kg)

1.50 + 0.04

0.78 + 0.04*

0.01 + 0.04*^

Change in Body Mass (%)

-1.9 + 0.0

-1.0 + 0.1*

0.0 + 0.1

Stomach Fullness at rest after 1st drink

1.1 + 0.1

1.6 + 0.3*

2.1 + 0.2*^

Stomach Fullness 10 min

1.1 + 0.1

1.4 + 0.2

1.6 + 0.2*

Stomach Fullness 30 min

1.1 + 0.1

2.4 + 0.2*

3.1 + 0.3*^

Stomach Fullness 45 min

1.1 + 0.1

2.3 + 0.3*

3.5 + 0.4*^

Stomach Fullness 60 min

1.1 + 0.1

1.9 + 0.4*

3.1 + 0.5*^

 

  • P<0.05 as compared with NF
  • ^P<0.05 as compared with FR-50

 

Other Findings

  •  Hydration status before exercise was similar in all 3 trials.
  • No difference in oxygen consumption during the initial 45 min of exercise between trials.
  • Rectal temperatures and HR were not significantly different between trials for any time point measured.
  • No significant differences between trials at any time point for RPE.
  • There were no significant differences in serum sodium between trials.  Serum sodium tended to be higher in the NF trial late in the exercise protocol.
  • Plasma volume declined to a similar extent during exercise in the 3 trials.
  • No significant differences in serum potassium, glucose and lactate between trials.
  • Amount of work performed during the 15-min performance ride was not different among the 3 trials.
  • No order effect existed between trials.
  • No significant differences in urine excretion following the exercise trials.
Author Conclusion:
Authors conclude that there appears to be no benefit from ingesting fluid during intense 1-h cycling exercise in mild environmental conditions since such ingestion has little effect on exercise HR, body temperature, plasma electrolytes or performance. 
Funding Source:
University/Hospital: Monash University
Reviewer Comments:

This study was conducted on male, highly trained cyclists/triathletes.  I would add those qualifications to their conclusion statement.  This question needs to be tested in females and a variety of athletes.  Additionally study was conducted in an air conditioned lab.  This question needs to be tested in the field setting. 

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? N/A
2. Was the selection of study subjects/patients free from bias? N/A
  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? 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? N/A
  2.4. Were the subjects/patients a representative sample of the relevant population? N/A
  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? N/A
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? N/A
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) N/A
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) N/A
  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
  3.4. 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
  3.5. 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? N/A
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? N/A
  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.) 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
  5.3. 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? N/A
6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? N/A
  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? 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
  6.3. 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
  6.4. 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
  6.5. 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? N/A
  6.8. In diagnostic study, were details of test administration and replication sufficient? N/A
  7. Were outcomes clearly defined and the measurements valid and reliable? N/A
7. Were outcomes clearly defined and the measurements valid and reliable? N/A
  7.1. Were primary and secondary endpoints described and relevant to the question? N/A
  7.1. Were primary and secondary endpoints described and relevant to the question? N/A
  7.2. Were nutrition measures appropriate to question and outcomes of concern? N/A
  7.2. Were nutrition measures appropriate to question and outcomes of concern? N/A
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? N/A
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? N/A
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? N/A
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? N/A
  7.5. Was the measurement of effect at an appropriate level of precision? N/A
  7.5. Was the measurement of effect at an appropriate level of precision? N/A
  7.6. Were other factors accounted for (measured) that could affect outcomes? N/A
  7.6. Were other factors accounted for (measured) that could affect outcomes? N/A
  7.7. Were the measurements conducted consistently across groups? N/A
  7.7. Were the measurements conducted consistently across groups? N/A
  8. Was the statistical analysis appropriate for the study design and type of outcome indicators? N/A
8. Was the statistical analysis appropriate for the study design and type of outcome indicators? N/A
  8.1. Were statistical analyses adequately described and the results reported appropriately? N/A
  8.1. Were statistical analyses adequately described and the results reported appropriately? N/A
  8.2. Were correct statistical tests used and assumptions of test not violated? N/A
  8.2. Were correct statistical tests used and assumptions of test not violated? N/A
  8.3. Were statistics reported with levels of significance and/or confidence intervals? N/A
  8.3. Were statistics reported with levels of significance and/or confidence intervals? 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
  8.4. 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
  8.5. 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? N/A
  8.6. Was clinical significance as well as statistical significance reported? N/A
  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? N/A
9. Are conclusions supported by results with biases and limitations taken into consideration? N/A
  9.1. Is there a discussion of findings? N/A
  9.1. Is there a discussion of findings? N/A
  9.2. Are biases and study limitations identified and discussed? N/A
  9.2. Are biases and study limitations identified and discussed? N/A
  10. Is bias due to study's funding or sponsorship unlikely? N/A
10. Is bias due to study's funding or sponsorship unlikely? N/A
  10.1. Were sources of funding and investigators' affiliations described? N/A
  10.1. Were sources of funding and investigators' affiliations described? N/A
  10.2. Was the study free from apparent conflict of interest? N/A
  10.2. Was the study free from apparent conflict of interest? N/A