Hydration and Physical Activity
Fallowfield JL, Williams C, Singh R. The influence of ingesting a carbohydrate-electrolyte beverage during 4 hours of recovery on subsequent endurance capacity, Int J Sport Nutrition 1995; 5: 285-299.PubMed ID: 8605516
Recruitment Not mentioned
Design RCT: subjects divided into matched groups according to ht, age, wt, VO2max, VEmax; within each matched pair, subjects were randomly assigned to control (P) or CE.
Blinding used (if applicable) Not mentioned, but assumed
Intervention (if applicable) Assignment to 1 of 2 treatments during recovery: Placebo (orange-flavored, sweetened water, 15.5±0.8 g CHO) or CE (noncarbonated, isotonic sports drink, 2.9% sucrose, 2.7% maltodextrin, 1.3% orange fruit, 52mg/100 ml Na, 14 mg/100 ml K, 6 mg/100ml Ca, 1 mg/100ml Mg) beverages. Equal vol of each solution for each group consumed immediately post-R1 and 2 h later.
Statistical Analysis Performance times compared by ANCOVA;
Changes in plasma FFA, glycerol, ammonia, Na, K; serum insulin; changes in body wt, plasma vol within each trial (Student's t-test for paired data). Differences in these variables (independent t-test).
Changes in capillary blood glucose, blood lactate, RER, HR, RPE, CRS, Temperatures (2-way ANOVA with repeated measures and Tukey post-hoc).
Significance at P<0.05.
Timing of Measurements
Pre-testing: 7d prior to start of study, subjects kept food intake diaries, nutritional content determined, and control diets providing same amts E and nutrient intake were prescribed for 48h prior to testing. VO2max determined, blood lactate obtained during treadmill running. Venous and capillary samples obtained.
Testing: 2 runs performed, separated by 4 h recovery. Run1 in the AM after 10h fast - emptied bladders, body weight obtained; HR and temp recorded before warm-up, at start of R1 & R2, and every 5 min suring exercise. Capillary samples taken at 30 and 60 min of each run. 5 min warm-up at 60% VO2max; then run at 70% VO2max; run for 90 min or until volitional fatigue. Expired gases collected over 60s, q. 15 min.
Recovery: 4 hr; ingested CE or P solutions immediately following R1 and again 2h later.
Post-testing: venous and capillary samples taken end of each run.
- Performance times
- Changes in: plasma FFA, glycerol, ammonia; Na & K (Flame photometry)
- Changes in: Serum insulin (radioimmunassay)
- Changes in Body wt, plasma vol (Dill & Costill method)
- Changes in capillary blood glucose, lactate, RER (calculated from VE, VO2, VCO2 gas analyses - Douglas bag --> gas meters), HR (ECG); RPE, CRS (scales); temperature (skin probes)
- Hgb (cyanmethemoglobin method)
Assignement to P or CE beverage.
Diet 48h prior to testing; lab temp during testing (20C); treadmill running at 70% VO2max
Initial N: 12 M, 4 F, trained
Attrition (final N):
Age: P group: 27.9±1.9; CE group: 26.1±1.3 yrs
Ethnicity: Not mentioned
Other relevant demographics: Run distances between 40-100 km/week
|ht (cm)||wt (kg)||VO2max (ml/kg/min)|
Running Speeds and Relative Exercise Intensities at Blood Lactate Concentrations of 2 mmol/L-1 and 4 mmol/L-1 of Treatment (CHO) Group and Control (P) (mean±SEM); Running Times and Carbohydrate oxidation at R1 and R2
Treatment Group (CE)
Statistical Significance of Group Difference
Running speed (m/s) at
Blood Lactate 2 mmol/L
Run Times (min)
CHO oxidation (%)
Blood glucose maintained in normal range during R1, both groups, serum Insulin decreased by 50%. Blood lactate increased w/onset of exercise; normal levels were restored in both groups during recovery, though concentrations were elevated in the CHO group vs P group (P<0.05). No differences between groups for blood lactate during R2.
Plasma FFA and plasma glycerol increased (p<0.01) during R1 in both groups. Plasma glycerol remained elevated in P following recovery (P<0.01), while FFA increased by 15% (p<0.01). Pre-R2 concentrations were elevated in p group (p<0.05). In CHO group, pre-R2 concentrations did not differ from pre-R1 after 4h recovery.
Absolute concentrations of ammonia same in both groups at end of exercise, despite differences in running performance between the 2 groups.
Plasma Na ns differences between groups during R1; plasma K sig increased by 19% both groups (P P<0.01; CHO p<0.05). NS differences from pre-R1 to 4hr post-recovery.
No differences in water ingestion during R1 between 2 groups. Plasma vol decre during R1, but restored during recovery. NS differences between groups in HR.
Sclaes: RPE and CRS higher in both groups during R2 vs R1 (p<0.01); higher ratings in P vs CHO group after 15 min of R2, and rest of R2 (RPE, p<0.05; CRS p<0.01).
Neither group restored pre-R1 body weight following 4h recovery (p<0.05). Est rehydration 65.9±6.3% in P and 62.6±7.3% in CHO (ns). Temp profile similar during R1 and R2; pre-R1 temp restored during P trial recovery, but remained elevated at start of R2 in CHO (p<0.05).
Ingesting 1g CHO/kg body wt at 2h intervals following prolonged, constant-pace running improved endurance capacity 4h later.
Provision of 6.9% CE solution facilitated rehydration as effectively as non-CHO Placebo solution.
Failure to maintain adequate CHO availability rather than failure to adequately rehydrate appeared to hasten onset of fatigue during a further bout of exercise.
|University/Hospital:||Loughborough University, London Hospital Medical College|
Quality Criteria Checklist: Primary Research
|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|
|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)||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|
|3.4.||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.)||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.)||???|
|5.3.||In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded?||???|
|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?||N/A|
|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?||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|
|9.1.||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|