Hydration and Physical Activity
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.
Dependent Variables
- 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)
Independent Variables
Assignement to P or CE beverage.
Control Variables
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
Anthropometrics
ht (cm) | wt (kg) | VO2max (ml/kg/min) | |
P | 173.9±2.5 | 68.8±3.4 | 57.6±2.1 |
CE | 174.3±2.4 | 68.8±4.6 | 59.5±1.7 |
Location: lab
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
Variables |
Treatment Group (CE)
|
Control group(P)
|
Statistical Significance of Group Difference |
Running speed (m/s) at Blood Lactate 2 mmol/L 4 mmol/L |
3.57±0.25 4.65±0.15 |
3.71±0.21 4.56±0.18 |
not reported |
VO2max (%) Blood Lactate: 2 mmol/L 4 mmol/L |
68.3±4.1 85.1±3.1 |
67.3±2.8 86.3±1.3 |
not reported |
Run Times (min) R1 R2 |
87.5±2.5 62.0±6.2* |
86.3±3.8 39.8±6.1 |
ns *P<0.05 |
CHO oxidation (%) R1 R2 |
47* 44* |
41 32 |
*P<0.05 |
Other Findings
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
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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 | |
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) | 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 | |