Hydration and Physical Activity


Wong SH, Williams C, Simpson M, Ogaki T. Influence of fluidintake pattern on short-term recovery from prolonged, submaximal running and subsequent exercise capacity.  Journal of Sports Sciences 1998; 16: 143-52.

PubMed ID: 9531003
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 if the pattern of fluid intake, with a carbohydrate-electrolyte solution (CES), during 4h of recovery from prolonged submaximal running influences subsequent endurance capacity.
Inclusion Criteria:
Well-trained university athletes; informed consent; no others mentioned
Exclusion Criteria:
None mentioned
Description of Study Protocol:

Recruitment not mentioned


Design experimental, randomized crossover: 2 experimental trials (consisting of T1, Recovery, T2), each trial separated by 7-10d; 1) ad libitum fluid consumption during recovery vs 2) fluid amt prescribed based on calculations of body mass loss during T1


Blinding used (if applicable) not mentioned


Intervention (if applicable)1) ad libitum fluid consumption (CES) during recovery vs 2) fluid (CES) amt prescribed based on calculations of body mass loss during T1.  CES was 6.9% Lucozade-Sport; 24 mmol 1-1; potassium, 2.6 mmol 1-1; calcium, 1.2 mmol 1-1; osmolality 300 mOsm kg-1


Statistical Analysis Student's t-test for paired data to compare performance times; data over time tested using 2-way ANOVA for repeated measures; Significant interactions analyzed by Tukey's post hoc analysis to identify differences between means; Paired t-tests to analyze total vol consumed, Uvol, and body mass chang; Sig level p<0.05.


Data Collection Summary:

Timing of Measurements

Pre-T1: Venous sample and capillary sample collected 

T1, 90 min: Warm-up; expired gases collected q.15 min;  capillary samples collected q. 30 min

Recovery, 3 h: consumed beverage ad lib or prescribed amt (q 60 min); capillary samples collected q 60 min

T2, to exhaustion: expired gases and capillary samples collected q. 15 min

Dependent Variables

  • Fluid volume consumed
  • Volume retained
  • Urine loss
  • Sweat/insensible losses
  • Plasma vol
  • Glu
  • Lactate
  • Insulin
  • FFA

Independent Variables

 Volume of CES consumed (ad lib versus calculated from body mass loss)

Control Variables

 controlled environmental conditions, working at 70% VO2max; T1 90 min; 4 h recovery

Description of Actual Data Sample:


Initial N: 5 F, 2 M

Attrition (final N): 7: 5F, 2M

Age: see table below for subject characteristics

Ethnicity: not mentioned

Other relevant demographics: well-trained university athletes, trained and competing regularly


  N=7, 5F, 2M
Age, yr 19.8±0.3
Ht, cm 168±3
Wt, kg 58.2±1.9
VO2max, ml/kg/min 57.5±3.3
HRmax, bpm 199±4

Location: Lab, Loughborough University, UK


Summary of Results:



Pre-T1 T1 Post-T1

Recovery Time (h) 1

Recovery Time (h) 2

Recovery Time (h) 3

Recovery Time (h) 4

Pre-T2 T2 Post-T2

Statistical Significance of Group Difference

Vol (ml)Ad lib, Vol (ml)Prescribed

--   --









-- -- --

* sig diff between trials, p<0.05

Time to complete run (min) Ad lib

Time, prescribed

--  90 -- -- --- -- -- --




-- p<0.05

CHO ingested throughout Recovery (g) Ad lib

CHO, prescribed

-- -- --




-- -- -- -- --  -- NS

Fat, CHO to TEE (%) Ad lib

Fat, CHO to TEE, prescribed


40, 60;


 40, 60

-- -- -- -- -- --

39, 61;


41, 59

-- ns

Body mass loss, % (kg)

Ad lib, prescribed





--  -- -- --








-- ns

Glucose, mmol/l (g/kg)

Ad lib, prescribed



























 * sig diff between trials, p<0.05


Ad lib, prescribed








-- --







Lactate, mmol/l

Ad lib, prescribed






-- -- -- --







FFA, mmol/l

Ad lib, prescribed






-- -- -- --








Other Findings

 Urine vol ns between treatments; after Recovery period, Plasma vol returned to initial level in ad lib, but not in prescribed intake trial.  At end of T2, plasma vol returned to normal in both trials (ns).  Blood glucose maintained in normal range in both trials (ns).  RPE increased similarly during T1 and T2 in both trials, and ns differences observed between trials for RPE or skin temp. 

Author Conclusion:
Drinking a prescibed volume of a CES after prolonged exercise, calculated to replace body fluid losses, restores endurance capacity to a great extent than ad libitum drinking during a 4h recovery, even though the total volumes ingested were the same.
Funding Source:
University/Hospital: Loughborough University (UK), Kyushu University
Reviewer Comments:
see paper for figure depicting changes in plasma vol over time, RER, and HR.  Very small sample size, large individual variance.
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? ???
  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? ???
  2.2. Were criteria applied equally to all study groups? ???
  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? ???
3. Were study groups comparable? ???
  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
  3.3. 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? ???
  3.5. 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.) Yes
  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? ???
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
  6.2. 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
  6.4. 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? 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
  7.6. 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? N/A
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