L'idratazione per l'esercizio fisico - Alberto Vincenzi - SINSEB
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L’idratazione per l’esercizio fisico
Alberto Vincenzi
Regolazione della Temperatura
Evaporation of 1L of
A1 water from the skin
will remove 573 kcal
of heat from the
body.
R.J. Maughan and E.R. Nadel, 2000, Temperature regulation and fluid and electrolyte balance
Diapositiva 2
A1 Athletes working twice as intensely would create 450 kilocalories of excess heat that would need to be dissipated over the
same 30 minutes to maintain body temperature. It is estimated that 1 milliliter of sweat can dissipate .5 kilocalorie, so over this
30-minute period the athlete would lose approximately 900 milliliters (almost 1 liter) of sweat. In 1 hour of high-intensity
activity, approximately 1.8 liters of water would be lost. On sunny and hot days when the heat of the sun is added to the heat
generated from muscular work, the athlete must produce more sweat
Alberto; 08/08/2018
Temperatura Interna Corporea
Galloway and Maughan (1997)
Fink et al. 2006
At dehydration rates of 7–10% humans stop exercising.
And when dehydration reaches levels of 15–20%, there is a risk of organ failure and death.
In cool laboratory conditions, VO2max has been shown to
decrease with fluid losses > 2% BW...
In the heat, sweat rates increase even more such that fluid
intake must be even more closely monitored.
100%
Exercise Capacity
80%
60%
0 1 2 3 4 5
Body weight loss (%)
Idratazione e Perdita di Prestazione
The absence of fluid
ingestion during
exercise leads to
dehydration and
reduced physiological
function.
from Craig and Cummings (1966)
from Pinchan et al. (1988)
Perchè la perdita di fluidi influenza la performance?
increase in plasma osmolarity (higher concentration of solute)
release of vasopressin (ADH) from the posterior pituitary gland.
ADH causes the kidney to re-absorb water
Urine volume goes DOWN dramatically to preserve blood osmolarity volume and pressure
As exercise progresses, the transfer of body
water into the plasma cannot keep up with
sweat losses so...performance decreases.
Quanti liquidi si
perdono?
M.N. Sawka and K.B. Pandolf, 1990
Heat loss via evaporation of sweat is largely
Effects of body water loss on physiological function and exercise performance dependent on the humidity
(proximate to the skin)
Perdite di liquiti in base all’intensità di
esercizio ed alla durata
A, 65% Vo2max., 33°C db (Montain & Coyle 1992)
B, marching in the desert (Adolph & Associates 1947);
C, 25% Vo2max., 49°C db (Sawka et al. 1985) Maughan (1985)
D, 45W, 34°C db (Strydom & Holdsworth 1968)
From Sawka et al. (1996).
• Reni: urina
• l’apparato digerente: feci (diarrea ‐ vomito)
Vie di dispersione • la cute: con il sudore e con la perspiratio insensibilis
• i polmoni: calore latente di vaporizzazione.
Cosa contiene il sudore?
Water is the second most essential nutrient,
following oxygen
Principali funzioni dell’acqua:
• Mantiene l’equilibrio termico fra le
cellule
• Consente il raffreddamento del corpo
From Maughan (1994).
• Rappresenta il solvente di molte sostanze
• Funge da protezione per il cervello e per
il midollo spinaleLa perdita individuale di fluidi varia notevolmente
fra atleti e fra differenti sport
There is great individual variability in sweat rates
amongst athletes,
ranging from 0.3 to 2.4 L/h and ∼1.2 L/h in runners.Come misurare il tasso di sudorazione?
Peso di partenza – peso alla fine = perdita di peso
Tasso di sudorazione (litri/orari)
(perdita di peso + volume di liquidi consumati – urina prodotta)
Durata dell’esercizio (in h)Cosa modifica i tasso di sudorazione
Idratazione e Reidratazione
1 • Urine Color Chart
2 • Assess Hydration
3 • 1, 2, or 3: Well
4 Hydrated
5 • 7 or Darker:
Dehydrated
6
7
8Ancora troppo presto per usare la saliva come
marker di idratazione
During exercise and heat exposures, saliva might be an
effective index to evaluate hydration status
but seems to be highly variable
(M Villiger ‐ European Journal of Clinical Nutrition ‐ 2018)Prima dell’evento 1. It is recommended that individuals consume a nutritionally balanced diet and drink adequate fluids during the 24‐hour period before 2. It is recommended that individuals drink about 500mL of fluid around 2 hours before exercise
Durante l’evento
1. During exercise, start drinking early and at regular intervals at a rate sufficient to
replace the water lost through sweating (i.e., body weight loss)
2. ingested fluids be cooler than ambient temperature 15° to 22°C and flavored to
enhance palatability
3. Addition of proper amounts of carbohydrates and/or electrolytes to a fluid
replacement solution is recommended for exercise events lasting longer than 1 hour
4. During intense exercise lasting longer than 1 hour; drinking solutions containing 4% to
8% carbohydrate at a rate of 600 to 1200 mL per hour. The carbohydrates can be
sugars (glucose or sucrose) or starch (e.g., maltodextrin)
5. Including sodium (0.5–0.7 g/L of water) during exercise lasting longer than 1 hour
(Baker & Jeukendrup2014)Come gestire l’idratazione ?
• Preferire invece l’acqua solo se si assume cibo, per ridurne
il carico osmotico (per 15’ dopo assunzione)
• Assumere sempre piccole assunzioni, le ischemie
enteriche indotte dal tipo di sforzo impongono carichi
costanti e modesti
0,24 cl – max
Ebden BD et al. 1994 Nutritional intake during an ultraendurance running race. Int J Sport Nutr.Fattori che influenzano lo svuotamento gastrico • Carbohydrate concentration in of the solution: < 7% carbohydrate, gastric emptying is not affected • Type of carbohydrate in the solution: smaller carbohydrate chain = slower the gastric emptying • Amount of fluid consumed: large volume = gastric emptying time faster. (420 to 660 ml) • Temperature of the solution: at rest fluids at body temperature leave the stomach quickly. During exercise cool fluids leave the stomach quickly • Relative hydration state of the athlete: dehydration and higher body temperatures = slower gastric emptying rate • Degree of mental stress: mental stress and anxiety = reduced gastric emptying • Type of physical activity: High‐intensity is associated with a slower gastric emptying rate
Effetti collaterali riguardo l’assunzione di
liquidi durante lo sforzo: ETAP
Exercise‐related Transient Abdominal Pain (ETAP)
• Athletes who drink large volumes
of fluid during exercise
• hypertonic drinks (e.g. soft drinks
or reconstituted fruit juices) or
beverages with similar high
carbohydrate concentration and
high osmolality, before and during
exercise.
• There is no ideal drink formula.POST EVENT – Recovery Drink • Sodium at a concentration equal to or greater than that of the sweat lost is required to maintain positive fluid balance (Shirreffs SM ‐ J Physiol Renal Physiol) • Carbohydrate: the addition of carbohydrate to rehydration drinks enhances fluid retention if the concentration of carbohydrate and volume of fluid ingested are sufficiently high (Clayton DJ ‐ Int J Sport Nutr Exerc Metab) • Water is not effective at maintaining fluid balance during recovery (Nose H ‐ J Appl Physiol) • Food and Fluid Ingestion: water is likely to be an effective rehydration drink when ingested alongside solid food (Miller J ‐ Proc Phys Soc)
POST EVENT ‐ RECOVERY
Gethin H. Evans - J Appl PhysiolCome valutare una bevanda per
la re‐idratazione?
Beverage Hydration Index:
the volume of urine produced after
drinking expressed relative to a
standard treatment
(still water) for each beverage!
Milk have been shown to enhance postexercise rehydration (Shirreffs SM ‐ Br J Nutr);
Protein might be recommended to enhance recovery, its addition may enhance rehydration (Watson P ‐ Eur J Appl Physiol)ACSM NATA AIS Gatorade NCAA
Before 500 ml : 2 hours 500-600 ml : 2-3 hours Ind 17 - 20 oz : 2 to 3 hours 17 - 18 oz : 2 hours
200-300 ml : 10-20 min 7-10 oz : 10 - 15 pre warm-up
8 oz every 10-15
During Regular Intervals 200-300 every 10-20 min Ind 7-10 oz every 10-15 min min
After Equal to loss 150% of weight lost Ind 20-24 oz / lb 20-24 oz / lb
Temp 59o - 72o F 50o - 59o F Ind Cooled 50o - 59o F
Contents CHO and Sodium CHO and Electrolytres Ind CHO (6-7%) and Sodium -L’obiettivo non dev’essere quello di
rimanere in bilancio pari,
ma di “contenere le perdite” entro il 2%
“0% dehydration” non porta alcun beneficio,
casomai un rischio di iperidratazione
‐ Sawka MN et al. 2007 Exercise and fluid replacement. Med Sci Sport Exerc.
‐ Noakes T. 2010 Drinking to thirst Optimum; Ann of Nutr & MetabIponatriemia:
lunghi lenti creano le condizioni più favorevoli all’insorgenza
Over‐drinking can cause water intoxication leading to
exercise‐associated hyponatremia (EAH) and/or
exercise‐associated hyponatremic encephalopathy (EAHE).
Mountain S.J. et al. 2006
Exercise associated hyponatriemia: quantitative analysis to understand the aethiogy. Br. J Sports Med.Soggetti a rischio iponatriemia
Recreational,
amateur or non‐elite
female marathon or
ultra‐marathon
runners who run at
slower speeds (8–9
km/h) and who drink
more fluids are at risk
of EAHDisidratazione: il più frequente problema
riscontrato nei lunghi e negli ultralunghi
Hiller WD 1989 Dehydration and hyponatremia during triathlons. Med Sci Sports Exerc.
Mayers LB Noakes TD. 2000 A guide to treating ironman triathletes at the finish line. Phys Sportsmed.
Eden BD et al. 1994 Nutritional intake during an ultraendurance running race. Int J Sport Nutr.ALCOOL & HYDRATION
Small amounts of alcohol to rehydration
drinks don’t inhibit the rehydration process,
although this is unlikely to be recommended
between bouts of exercise on the same day
(Desbrow B, ‐ Int J Sport Nutr Exerc Metab)Caffè e Idratazione Maughan RJ, Nutr Diet. 2003
Differenze di genere
A bassa intensità non ci sono
differenze
Mano a mano che aumenta
l’intensità, aumentano le differenze
con una minore efficacia della
sudorazione, circa l’omeostasi
termica, nella donna
Ichinose‐Kuwahara T. et al. 2010
Sex differences in the effects of physical training on sweat gland responses during a graded exercise. Exp. PhysiolTAKE HOME MESSAGE • Una buona idratazione è fondamentale per lo stato di salute e per la Performance • Essere ben idratati significa iniziare ad idratarsi sin dalle prime ore del mattino e durante tutto l’arco della giornata • Una disidratazione >2% influisce negativamente sulla performance, mentre l’iperidratazione diluisce il Sodio nel sangue aumentando il rischio di Iponatremia • Prima dello sforzo basta bere acqua naturale non gasata e possibilmente non fredda; durante lo sforzo privilegia una bevanda isotonica che contenga una adeguata percentuale di carboidrati (5-7%) e di elettroliti (sodio/potassio) • L’acqua di cocco può essere una valida alternativa ai comuni sport drink ma con pochi cho(3-4%) e piu potassio che sodio • Dopo lo sforzo una birra a bassa gradazione alcolica o anche meglio analcolica è ricca di liquidi, zuccheri e sali minerali e non interferisce negativamente con i “markers” dell’idratazione. • Dopo lo sforzo evitare altri tipi di alcolici
GRAZIE PER L’ATTENZIONE
Domande?
Dott.alberto.vincenzi@gmail.com
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