Hydration and Physical Activity
To evaluate the effects of a 7%CES (versus water) on physiological responses, hydration status, exercise performance in male distance runners during simulated outdoor 40-km road race under warm, humid conditions.
training >65 km/week; completion of 32-km training run in previous month; use of programmed drinking during run training; informed consent.
none mentioned.
Recruitment not mentioned
Design
randomized, double-blind crossover study in field setting; 2 conditions assigned in counter-balanced fashion.
Blinding used (if applicable)
Double-blind, randomized assignment of drink conditions.
Intervention (if applicable)
During 40-km run, given 1 of 2 drink conditions: water or 7% CES (250 ml/5 km, which was equivalent to dose of 0.75 l/h)
Statistical Analysis
ANOVA with repeated measures; Student's t-test for dependent samples; sig level of P<0.05.
Timing of Measurements
Instructed to consume typical pre-competition diet for 3d prior to 1st trial, and replicate this for the 2nd trial; no exercise during the 24h prior to trial.
Day of trial, consumed water, but no solid food; 30 min prior to run, consumed 400 ml of either 7%CES or water. Trial conducted outdoors in summer (25C-32C, 82%-62%RH change across test sessions from beginning to end of trial). Temp between trials was not significant.
Trial: 5Km loop completed 8x for distance of 40 km. 2-4 runners tested during each session. 250 ml of drink administered every 5 km, RPE, temp, and HR recorded; break at 20 km for blood sample, weight.
At end of trial, drink beverage ad libitum during 30 min recovery period.
Dependent Variables
- RER and VO2 (Douglas bag method)
- HR
- RPE
- body weight
- Sweat rate (net change in body weight, corrected for fluid)
- Core temp
- Glucose, total pro, BUN
- Electrolytes and Hgb (reflectance spectrometry)
- Plasma lactate (analyzer)
- Hct
- Posm (freezing point depression)
- Pvol (from hgb, hct)
Independent Variables
Drink condition:
Water
7%CES: 5% glu, 2% fructose, 9.7 mmol/l Na and Cl; 5 mmol/l K.
Control Variables
drink volume and timing, timing of measurments; distance of run
Initial N: N=8M
Attrition (final N): N=8M
Age: see table below.
Ethnicity: not mentioned
Other relevant demographics: none mentioned.
Anthropometrics (e.g., were groups same or different on important measures)
Age (yr) | 32.1±6.0 |
Ht (cm) | 186.7±5.1 |
Wt (kg) | 70.5±7.2 |
%Body fat | 8.7±1.1 |
VO2max (ml/kg/min) | 69.8±3.7 |
HRmax (bpm) | 191.4±11.5 |
Training distance (km/wk) | 86.6±19.2 |
Best marathon time (min) | 156.4±17.4 |
Location:
Outdoors; Atlanta, GA (summer season)
Variables |
Total duration of run (water; CES) |
20 km (Water; CES) |
40 km (Water; CES) |
Recovery (Water; CES) |
Statistical Significance of Group Difference |
Fluid intake (l/hr) |
0.78; 0.79 |
|
NS |
||
Body weight loss (%) |
-2.3; -2.5 |
-4.4; -4.5 |
-3.9; -4.1 |
NS between trials |
|
Sweat rate (l/h) | 1.8 | NS | |||
Urine output (kg) |
0.1; 0.2 |
|
NS |
||
Run time, first 35 km (min) | 149±4.2; 149.9±5.0 | NS | |||
Performance during last 5 km (min) | 24.4±1.5; 21.9±1.0* | *P<0.03 CES vs water |
Other Findings
No differences between the 2 drink trials for serum electrolytes, blood lactate, total pro, BUN, Osm, %change Pvol, RER, HR, RPE, blood pressure.
Blood glucose sig higher (P<0.01) throughout 40K and recovery during CES vs water.
%VO2max sig higher (P<0.05) at 5K when consuming water (70.4%) vs CES (66.6%)
7% CES is similar to water as a fluid replacement drink interms of thermoregulation, maintenance of phsiological function, hydration status. However, the 7% CES increased blood glucose and had a significant regogenic effect on prolonged running, and thus may confer a benefit to highly-trained marathoners competing in the heat.
Government: | NIH |
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? | 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? | 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? | N/A | |
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? | 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? | Yes | |
5.1. | In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? | Yes | |
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? | 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? | N/A | |
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? | N/A | |
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 | |