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Hydration and Physical Activity


Bachle L, Eckerson J, Albertson L, Ebersole K, Good win J, Petzel J.  The effect of fluid replacement on endurance performance, J Strength and Conditioning Research 2001; 15 (2): 217-224.

PubMed ID: 11710407
Study Design:
Randomized Crossover Trial
C - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:
To examine the effects of carbohydrate ingestion and fluid replacement on endurance performance (power output (PO), rating of perceived exertion (RPE), heart rate (HR)), body weight (BW), urine osmolarity (Uosm), urine electrolytes (Una, Uk, Ucl), and sweat rate (SR).
Inclusion Criteria:

Informed consent, recreational, but not competitive athletes

Exclusion Criteria:

none mentioned

Description of Study Protocol:

Recruitment none mentioned


Design randomized crossover


Blinding used (if applicable) none mentioned


Intervention (if applicable) given 1200 ml to consume ad libitum during 60 min of exercise of either distilled water or CES; or no fluid.


Statistical Analysis 1- and 2-way repeated measures and mixed factorials ANOVA (between trials, trial X time, pre-/post-ex comparisons);  Tukey's post hoc  tests to locate differences; Dependent t-tests;  Significant at P<0.05.


Data Collection Summary:

Timing of Measurements

 Void urine (collect sample); Ht, wt, body density (skinfolds), %BF (Siri) measured. 

5 min warm-up on cycle, generate highest PO for 60 min, keeping pedal cadence constant (40-80 RPMs).  Subjects were fanned (in temp/humidity-controled environmnent, 21C, 72%RH) and able to watch video while cycling.  Chilled drinks were consumed ad lib over the 60 min (vol of 1200 ml).  HR, PO monitored every minute.  RPE rated every 5 min. 

At end of ride, wt recorded, voided urine (collect sample). 


Dependent Variables

  • Anthrompometrics (ht, wt, density)
  • Uosm (vaporpressure osmometer)
  • Una, Uk (flame photometry)
  • Ucl (chloriometer)
  • Sweat rate (change in wt, fluid intake, Uvol)

Independent Variables

 Beverage (water, 6% CES) or no beverage consumed during exercise.

Control Variables

Environment, fluid vol (1200 ml), cadence (RPMs), calculation of sweat rate.


Description of Actual Data Sample:

Initial N: 4 M, 6 F recreational athletes

Attrition (final N):

Age: 29+2 yr

Ethnicity: not mentioned

Other relevant demographics: n/a

Anthropometrics: 169.7+2.6 cm; 67.38+4.64 kg; 20.8+2.0 %BF

Location: Lab


Summary of Results:



Pre-ex; Post-ex

No Fluid




Statistical Significance of Group Difference

Body weight (kg)

70.74±4.64; 70.02±4.63

 70.52±4.48; 71.11±4.63*

70.80±4.62; 71.38±4.60*

 *P<0.001 vs NF

Una (mEq/l)

 94±16; 63±10*

 90±20; 47±12**

 123±18; 69±15***

* P<0.02; **P<0.002; ***P<0.004


 137±21; 135±19

113±13; 77±15* 

 147±24; 93±16**

 *P<0.015; **P<0.029

Uk  77±13; 110±15* 72±21; 70±17   56±8; 93±16 *P<0.02
Uosm (mOsm/kg)  673±90; 676±78  594±94; 506±89 657±88; 532±86  NS


Other Findings

 No significant differences between trials for power output, RPE, HR, sweat rate, though urinary electrolytes were decreased after exercise in the beverage trials (P<0.05). 

There was a sig increase in body weight after exercise in the beverage trials (P<0.001) versus no fluid. 

CES no better than water at enhancing performance or hydrating when consumed during exercise.

Author Conclusion:

Fluid replacement with or without CES during 1-hour of intense cycling does not appear to enhance endurance performance in hydrated, recreational athletes.

Carbohydrate and electrolyte supplementation appears to be unwarranted for this type of exercise.

Funding Source:
Reviewer Comments:

Small sample, though conducted to try to replicate a free-living setting.  Cycling may not have been "intense" enough to make treatment meaningful. 

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
  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? 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
  2.2. Were criteria applied equally to all study groups? 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
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
  3.2. 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
  3.4. 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")? 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
  4.2. 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
  4.4. 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
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? ???
  5.2. 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? N/A
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? Yes
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? ???
  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
  6.6. 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
  6.8. 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? ???
  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? 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
  8.1. 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)? Yes
  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? No
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