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Hydration and Physical ActivityRisks, Challenges, and Benefits

Continuing Professional Education Program

Presented by The Coca-Cola Company Beverage Institute For Health & Wellness

Ronald Maughan, PhD, FACSMProfessor, Sport and Exercise Nutrition

Loughborough University

Bob Murray, PhD, FACSMFounder, Sports Science Insights, LLC

Moderator

Diane Quagliani, RD, MBAQuagliani Communications, Inc.

SpeakerSpeaker

Hydration, Health Hydration, Health and Performanceand Performance

Ron Maughan, Loughborough University

Speaker

Some key questionsSome key questions• How much should we drink?

• How much is too little? How much is too much?

• Are there significant health risks associated with inappropriate hydration?• Acute and chronic effects on health

• Are there significant performance risks associated with inappropriate hydration?• Physical performance; skilled tasks; cognitive; mood

• Are specific groups at risk of inappropriate hydration?• Can we assess drinking behaviour and hydration status?

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How much should I drink?How much should I drink?

Ask Google:

“How much should I drink?”

Top listed website:

WaterAid UK

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Infants 0-6 mo 100-190 mL/kg per dayInfants 6-12 mo 800-1000 mL/day Infants 1-2y 1100-1200 mL/day Children 2-3 y 1300 mL/day Children 4-8 y 1600 mL/day Boys 9-13 y 2100 mL/day Girls 9-13 y 1900 ml/dayAdult females 2.0 L/dayAdult males 2.5 L/day

Adequate Daily Water IntakesAdequate Daily Water Intakes

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“The vast majority of healthy people adequately meet their daily hydration needs by letting thirst be their guide. The report did not specify exact requirements for water, but set general recommendations for women at approximately 2.7 liters (91 ounces) of total water - from all beverages and foods - each day, and men an average of approximately 3.7 liters (125 ounces daily) of total water. The panel did not set an upper level for water.

About 80 percent of people's total water intake comes from drinking water and beverages - including caffeinated beverages - and the other 20 percent is derived from food.

Prolonged physical activity and heat exposure will increase water losses and therefore may raise daily fluid needs, although it isimportant to note that excessive amounts can be life-threatening. “

What does this mean for me?What does this mean for me?

Do the “general recommendations” apply to me?

How do I know if I need more or less than the average?

What are the likely consequences of failing to ensure an adequate hydration status?

Answers likely depend on many factors

Who am I?Who am I?

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Hydration and healthHydration and health

There is good evidence for a link between poor hydration and:

Increased risk of kidney stones

Constipation

Coronary heart disease

Stroke

Hyperglycaemia in diabetic ketoacidosis

Hydration and healthHydration and health

There is some evidence for a link between poor hydration and:

Renal disease

Bladder and colorectal cancer

Dental diseases

Broncho-pulmonary disorders

(How strong does the evidence have to be before it’s worth doing something about it?)

If sufficiently severe, dehydration If sufficiently severe, dehydration will causewill causeReduced physical performanceReduced physical performanceReduced blood volume Impaired thermoregulationIncreased heart rate

Headache, nausea, insomniaImpaired mental functionImpaired mental function

Loss of acclimation benefitsIncreased risk of heat illness

Increased perception of effortIncreased perception of effort

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We should consider:We should consider:

Effects of starting exercise in a hypohydrated state

Effects of progressive dehydration during exercise

Meta-Analysis of the Effects of Pre-Exercise Hypohydration on Endurance Performance, Lactate Threshold and VO2max

Pierre-Yves Gigou1,2, Martin Lamontagne-Lacasse1,2, Eric D.B. Goulet1,2.

1Faculty of Physical Education and Sports, Université de Sherbrooke, Sherbrooke, QC;2 Research Centre on Aging, Université de Sherbrooke.

Exercise-induced dehydration (EID) ≥ 2% bodyweight (BW) impairs endurance performance (EP). It is unclear how pre-exercise hypohydration (PEH), which may impose physiological challenges differing from those of EID, affects EP, VO2 at lactate threshold (VO2LT) and maximal oxygen consumption (VO2max).

PURPOSE: To determine the magnitude of the effects of PEH on EP, VO2LT and VO2max using a meta-analytic approach.

METHODS: Studies were located via database searches and cross-referencing. Inclusion criteria: BW loss incurred > 1h prior to the exercise tests; hydration level in the control group < 0.5% > -1% BW; hypohydration level in the experimental group > 1% BW and > 0.5% than control. Exclusion criteria: diuretics- and caloric restriction-induced BW loss.

STATISTICS: Random-effect model for mean weighted summary effects, random-effect (method-of-moments) meta-regression for relationships between variables and random-effect analog to the ANOVA for subgroup analyses. Mean changes in EP times during incremental or fixed-power output tests to exhaustion were converted to mean changes in power output.

RESULTS: Twenty-nine research articles were retrieved, among which 10, 7 and 7 met the inclusion criteria for EP, VO2LT and VO2max, respectively, providing 14, 10 and 11 effect estimates. Mean BW decreases in all experimental groups were 3.9 ± 0.9% (SD) (range 2.6 to 5.6%). EP and VO2LT: Mean exercise test times among studies was 21 ± 15 min. Mean power output fell by 3.2% (95% CI: 2.4 to 4.0%) and VO2LT by 5.63% (95% CI: 2.8 to 8.4%) in hypohydrated group relative to control. Percent change in power output and VO2LT did not differ between studies with BW losses ≤ 4% or > 4%. Meta-regression analyses did not establish significant relationship patterns between BW losses and percent changes in power output or VO2LTs. VO2max: With PEH VO2max decreased by 2.4% (95% CI: 1.1 to 3.8%) compared with control group. Percent change in VO2max in studies with BW losses ≤ 4% was significantly lower than in those with BW losses > 4%. VO2max was found to decrease by 2.9% for each percent loss in BW above a threshold loss of 3.1% (P = 0.027).

CONCLUSIONS: Results indicate that PEH ≥ 3% BW impairs EP, VO2LT and VO2max in a practically important manner. Studies are required to establish how PEH in the 1-5% BW range affects EP during prolonged exercise.

“Mean power output fell by 3.2% (95% CI: 2.4 to 4.0%) in hypohydrated group relative to control.

With PEH, VO2max decreased by 2.4% (95% CI: 1.1 to 3.8%) compared with control group.

Results indicate that PEH ≥ 3% BW impairs EP and VO2max in a practically important manner.”

The bottom lineThe bottom line

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• Dehydration, if sufficiently severe, can impair performance in most events, particularly in warm and high-altitude environments. Athletes should be well hydrated before exercise and drink sufficient fluid during exercise to limit dehydration to less than about 2% of body mass.

• Ingestion of even small amounts of carbohydrate during exercise can enhance cognitive and physical performance in competition lasting one hour.

• Chilled fluids may benefit performance in hot conditions.

• Athletes should not drink so much that they gain weight during exercise.

• Sodium should be included when sweat losses are high, especially when exercise lasts more than about 2 hours.

• During recovery from exercise, rehydration should include replacement of both water and salts lost in sweat.

• IOC Consensus Statement on Sports Nutrition 2010

Effects of acute dehydration Effects of acute dehydration

To assess some of the effects of hydration on mood and brain function, 15 healthy adults participated in 2 trials:

In one trial, fluid intake was restricted for 37 h and normal drinking was allowed in the other trial.

A number of subjective responses were measured by questionnaire.

Shirreffs et al, 2004

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Hydration & cognition in childrenHydration & cognition in children

40 children, mean age 8.6 y

Cognitive tests in afternoon

+/- 300 ml tap water, crossover

tested 20 or 35 min after drinking

Memory better (p < 0.03) with drinking

No effect on sustained attention (p=0.06)

Benton & Burgess (2009) Appetite 53, 143-146

Hydration & cognition in Hydration & cognition in childrenchildren

58 children aged 7-9 y

Up to 250 ml water vs control group

Testing 20 min after drinking

Drinking group performed better on

visual attention task (p = 0.02)

memory task (p < o.02)

Edmonds & Burford (2009) Appetite 52, 776-779

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At the other end of the age range . .At the other end of the age range . .

Chronic hypohydration in the elderly, may be associated with a decline in physical function and in cognitive status

Renal concentrating capacity decreases with age

Hypohydration may be due in part to a reduced thirst sensation

Some drugs may suppress thirst: SSRI’s, ACE inhibitors, anti-Parkinson drugs

Acute dehydration may be a precipitating factor in hospital admission

Hydration and Quality of LifeHydration and Quality of Life

Subjects: 82 residents of four care facilities for the elderly

Outcomes were measured using the CCI Tool and QoL data was obtained using the Australian WHOQOL-100

Hydration, falls and depression were most often associated with poorer resident QoL and as such appear to be key areas for clinical management in residential aged care.

Courtney et al (2009) Aust J Adv Nurs 26,49-57

Is it really a problem?Is it really a problem?

Warren et al (1994) The burden and outcomes associated with dehydration among US elderly, 1991. Am J Public Health 84, 1265-1269

Data from 1991 Medicare files

Age, race, sex, plus up to 5 diagnoses

Hospitalisation FOR dehydration

Hospitalisation WITH dehydration

Dates of admission, discharge and death (up to 2 y)

Costs reimbursed

Analysis limited to

Black or White, aged 65-99 y

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Prevalence and costsPrevalence and costs

Warren et al (1994) The burden and outcomes associated with dehydration among US elderly, 1991. Am J Public Health 84, 1265-1269

1.4%: dehydration as principal diagnosis

146,960 hospitalisations

Total reimbursement: $446 million

6.7%: dehydration as any diagnosis

731,695 hospitalisations

Risks of dehydrationRisks of dehydrationEarly (30 d) mortality per 100 admissions 17.4

Late (31-365 d) mortality per 100 admissions 30.6

Dehydration Hip fracture

30 d mortality 17.4% 6.4%

1 y mortality 48% 20%

Warren et al (1994) The burden and outcomes associated with dehydration among US elderly, 1991. Am J Public Health 84, 1265-1269

Heat, hydration & mortalityHeat, hydration & mortality

France, 2003: From 1-20 August, mean temperature exceeded seasonal norm by 11-12°C

Mortality records from Inserm and INSEE

Compared with rates from 2000-2002 for same period

O-E (observed – expected) = excess mortality

O/E = mortality ratio

Fouillet et al (2006) Excess mortality related to the August 2003 heat wave in France. Int Arch Occup Environ Health 80, 16-24

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Meanwhile, elsewhere in EuropeMeanwhile, elsewhere in Europe

Excess Mortality

Portugal 1316

Spain 6595-8648

Italy 3134

England & Wales 2139

Netherlands 1400-2200

Switzerland 975

ConclusionConclusionAcute dehydration, if sufficiently severe, will:

Impair physical performance

Impair mental performance

Precipitate vascular (& other) events

Exacerbate existing conditions

Chronic dehydration will:

Increase risk of some diseases

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Thank youThank you