EAL

Hydration and Physical Activity

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To investigate the effect of a high and low post-exercise ingestion rates of carbohydrate-electrolyte solution on the efficacy to restore plasma volume and fluid balance.

Inclusion Criteria:

Well-trained, informed consent (no others mentioned)

Exclusion Criteria:

None mentioned

Description of Study Protocol:

Recruitment Not mentioned

Design Randomized, crossover; 2 exercise tests, 1 week apart; each session with 5hr recovery/rehydration period.

Blinding used (if applicable) Not mentioned

Intervention (if applicable) Rate of fluid (Carbohydrate-electrolyte solution, CES) intake:

High, H: ingested 60, 40 and 20% of solution in the 1st, 2nd, and 3rd hours (respectively) of recovery period (amount equivalent to 120% body weight loss)

Low, L: ingested equal volume at a rate of 24% of Body weight loss/hr during the 5 hour recovery period.

Prescribed volume of drink always ingested within 1st 20 min of each hour period.

Statistical Analysis Significance between treatments assessed by Wilcoxon's signed-rank test. Friedman's test carried out to determine significane over time, and differences were located by Wilcoxon's signed-rank test. Bonferroni correction applied to adjust for multiple comparisons. Sig level of p<0.05.

Data Collection Summary:

Timing of Measurements

Testing: W max determined in a pretest; On test day, standardized breakfast 2h before exercise; Emptied bladder, BW taken; catheter inserted in vein for blood sampling prior to ex; cycling at 50% Wmax (=60% VO2max) in environmental chamber to dehydrate 3% BW (=100-120 min); BW obtained; 15 min between end of testing and recovery period. Blood samples taken after exercise

Recovery: 6 hrs total, temp-controlled environment; ingest CES (=120% BW loss) at different rates (H vs L), drinking prescribed volume during first 20 min of each recovery hour. Standardized lunch consumed after 3h recovery. Blood samples taken at beginning of recovery and after .5, 1, 1.5, 2, 3, 4, 5, and 6 hours of recovery. At end of recovery, urinated as much as possible into bottle.

Dependent Variables

Changes in plasma vol (calculated from hct and hgb)
Posm (freezing depression)
Plasma Na and K; Cl (flame photometer; coulometric titration)
Rehydration, changes in fluid balance ( sweat loss as change in BW during ex, fluid intake, urine output during recovery)
Na balance (difference in Na intake from drink and food, losses in urine, assuming avg sweat [NA] = 50.8mM)
Urine output (after each hour of recovery was weighed to calc Uoutput over time, total urine loss)
Urine K, Na, Cl (see Plasma Na, K, Cl)

Independent Variables: Ingestion rate of CES (H or L) during recovery period

Control Variables: Environmental chamber temp for exercise (28C, 50-60%RH); Temp-controlled environment for recovery (20C); Drink temp (5-10C); drink amout (=120% Body weight loss); drink ingestion (within first 20 min of each recovery hour period); standardized breakfast before test session; standardized lunch after 3 hours of recovery.

Description of Actual Data Sample:

Initial N: 8 well-trained M

Attrition (final N): 8 M

Age: 23±2 years

Ethnicity: not mentioned

Other relevant demographics: cyclists and triathletes

Anthropometrics

Weight: 73.2±1.8 kg; Height: 186±2 cm; Max work capacity: 406±10 W (lower day-to-day variation than VO2max, Kuipers et al, 1985)

Location: Lab, Maastricht University, The Netherlands

Summary of Results:

Variables	High (H) rate of CES ingestion	Low (L) rate of CES ingestion	All subjects	Statistical Significance of Trial Difference
Change in Body Weight during exercise (kg)	n/a	n/a	2.192±0.056 (3±0.07%)	ns
Drink intake: H (kg):recovery hours 1-3 L (kg/h)over 5 hr period	1: 1.315±0.051, 2: 0.877±0.034, 3: 0.438±0.017	0.526±0.027	n/a	not reported
Total Urine output (kg)	0.839±0.112	0.910±0.146	n/a	ns
Net fluid balance (%)	82±5	79±6	n/a	ns
Plasma Osm increase during exercise (Mosm/kg)	n/a	n/a	5.8±0.7	p<0.01

Other Findings

Urine output:

Recovery hour 1 (T1): tended to be higher in L vs H (p<0.1); T2-3, H higher than L (P,0.05);6 L higher than H (p<0.05) T3-4 H higher than L (cumulative, p<0.05); T5-6 L higher than H (P<0.05).

Urine electrolytes: ns differences between 2 trials; Na-balance was negative and ns in both trials.

Plasma volume: during exercise ns difference between trials; post-exercise, returned to pre-exercise level within 30 min in both trials; Change during R: rapid initial increase followed by short decrease, and subsequent further increase (due to fluid shifts and urine production); Restored faster in H vs L, T2-T3 (p<0.05) and exceeded pre-ex level T1-T5 (p<0.05).

PLasma electrolytes:Na and K increased during exercise in L (p<0.05), and decreased with rehydration below pre-ex level in both trials. Ns differences for plasma K and Na at any time point during recovery; Cl not affected by exercise, but decreased faster in H vs L with rehydration (p<0.05), and tended to be lower at T2-3 vs L (p<0.1).

Author Conclusion:

When a fast restoration of fluid losses for maintenance of exercise capacity is needed (i.e. repeated bouts of exercise or competition by weight class), a high and forced rate of intake of a well-composed solution is especially important. It is also advisable to maintain this high rate throughout the recovery period.

If recovery time to next exercise session is substantial, fluid replacement can be met by a lower drink intake over a prolonged time period.

Funding Source:

University/Hospital:

University of Maastricht (Netherlands)

Reviewer Comments:

See paper for Figures of results (Urine output, Fluid balance, plasma vol, electrolyte and Posm changes)

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?	N/A
	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?	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?	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.)	Yes
	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?	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