Hydration: Body Water Balance and Physiological Responses to Exercise

Aims and Objectives of Performance Nutrition

1 Understand The theory behind water balance and regulation within the body 2 Discuss How hydration impacts physiological responses to exercise and the impact on exercise performance 3 Critically Analyse The importance of fluid balance pre, during and post exerciseslido

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Hydration Recall and Poll Results

What do you remember about hydration from last year? O Start presenting to display the poll results on this slide.

Fluid Loss, Gain, and Compartments

Respiratory tract Gastrointestinal tract 2 25" Universiad A Belgrade 2009 100 E TAKETCH MEMORIAL MACHADE, SERBIA, 2007 GI: Fluid intake RBC Plasma (intravascular fluid) RBC RBC RBC IV Compartment % of Body Water % of Body Mass Amount (L) Total Body Water 100 60 42 Intracellular Fluid 65 39 27 Extracellular Fluid 35 21 15 Interstitial Fluid 28 17 12 Intravascular Fluid 7 4 3 Skin (sweat) Urinary system GI: Food intake Intracellular fluid (ICF) Interstitial fluid Extracellular fluid (ECF)

Hydration States and Body Water Content

Hyperhydration Dehydration Euhydration Dehydration Rehydration Hypohydration

Factors Affecting Body Water Content

1. Adipose Tissue vs Lean Tissue
2. Gender
3. Training Status
4. Age

Normal Body Chemistry and Osmolality

Normal body chemistry · Plasma osmolality <290 mosmol.kg · Urine osmolality <700 mosmol.kg · Urine specific gravity < 1.020 • Osmolarity describes the concentration of solute (number of particles) in a solution/fluid · Tonicity describes how extracellular fluid can change the volume of a cell via osmosis

Water Balance and Regulation

• 1 plasma osmolality activates hypothalamic osmoreceptors and send a signal to the hypothalamus
• Stimulates the secretion of Arginine Vasopressin by the posterior pituitary gland
• î plasma vasopressin = 1 renal water absorption and water excretion l
• ^ water reabsorption \ plasma osmolality . Osmoreceptor's in the hypothalamus also stimulate thirst and promote seeking of fluid to help restore plasma osmolality
• High plasma osmolality is anything >290-295 mOsm per kilogram Knepper, Kwon and Nielsen (2015) Plasma osmolality Drinking + + HYPOTHALAMUS Osmoreceptor activation Thirst SON PVN + AVP secretion PITUITARY GLAND + Plasma vasopressin Water reabsorption + - Vasopressin- receptor activation KIDNEY Water excretion

Vasopressin and Aquaporin Activation

INTERSTITIAL SPACE Vasopressin Knepper et al. (2015) - Vasopressin V2 receptor INTERCALATED CELL Adenylyl cyclase 6 Gas PRINCIPAL CELL Recycling vesicle ATP 0 CAMP Endocytosis - Aquaporin-2 O C O Aquaporin-3 Activation of protein kinases Phosphorylation of aquaporin-2 Exocytic insertion to apical membrane LUMEN Aquaporin-4 Activation of transcription factors O Increased AQP2 O O NUCI CIELIS transcription O Water

Water Balance and Regulation of Urine Concentration

Dilute Urine Concentrated Urine 110- 100 90- 80- Rate (ul/min) 70- 60 50- Osmolar clearance 40- 30- 20- Water excretion 10- 0 1 10 100 Plasma Vasopressin Concentration (pmol/liter) • levels of AVP = V water excretion · Solute excretion remains constant (Osmolar clearance) . ^urine concentration (concentrated) = + vasopressin concentration • urine concentration (dilute) = vasopressin concentration · ^ renal absorption in response to T AVP = \ plasma osmolality · _ Stimulus for AVP secretion and thirst · Completes feedback loop & return to a euhydrated state

Dehydration: Effects and Electrolytes

1. What happens when we become dehydrated? 2. What are the key electrolytes and their amounts in the intracellular and extracellular fluid? WATER PLEASE Dry Mouth Headache Dry Skin Bad Breath Fuzzy Thinking Dizziness

Dehydration and Performance Impairment

(Cheuvront et al. 2007; Zouhal et al. 2011; Volpe, Poule and Bland, 2009) 160 140 Type Intracellular dehydration ≥ 2% Body mass 120 No. of Student-Athletes 100 TBW deficit -1.4 L Plasma volume 80 60 40 20 0 - Hydration Status Physiologic compensation Renal water retention Water acquisition Euhydrated Hypohydrated [ Significantly hypohydrated Dehydration >2% body mass loss impairs performance • · Extremely common for athlete to start exercise dehydrated (Volpe, Poule and Bland,2009) · Athlete can change states during exercise. It's very common for athlete to become hypohydrated · Athlete who finish faster are the most dehydrated (Cheuvront et al.2007; Zouhal et al. 2011) · Is a level of dehydration okay for performance? Sweat (mmol/l) Plasma (ECF) (mmol/l) Plasma (ICF) (mmol/l) Threshold > 2% A Posm Sodium 20-80 130-155 10 Response AVP Thirst Potassium 4-8 3.2-5.5 150 1 Osmotic

Summary of Water Balance and Hydration

Water balance is control by vasopressin and when we become dehydrated the osmoreceptors upregulate AVP to increase water absorption and stimulates thirst. Extremely common for athlete to be hypohydrated prior to performance or become hypohydrated during performance Drink volume is vital as most athlete under drink and sodium is extremely important for rehydration

Hyperhydration Before and During Exercise

1) Na Na Na <135 mmol/l Normal = 136-142 mmol/l 3) Hypertonic Disrupted osmotic balance 2) 4) A. Normal Fig. 2. Computer tomography scans of the brain B. Cerebral edema

Causes and Prevention of Hyperhydration

Who? · Athletes in hot humid climates that over drink prior to exercise performance Causes . SIAH - Syndrome of Inappropriate Antidiuretic Hormone · Abuse of anti-inflammatory drugs Prevent · Fluid consumption does not exceed sweat loss . Ingest sodium containing foods and beverages to help replace sodium lost in sweat

Dehydration and Physiological Effects on Heart Rate and Stroke Volume

Category Amount (% of fluid lost in sweat) Dehydration (magnitude of BW loss) No Fluid 0 4.2 ± 0.1% Small Fluid 20 ± 1% 3.4 ± 0.1% Medium Fluid 48 ± 2% 2.3 ± 0.1% Large Fluid 81 ± 2% 1.1 ± 0.1% · Different dehydration rates, induced by different fluid volumes during 2 hours of exercise (62-67% O2 maximal) · Trained endurance cyclist x 8 Moutain & Coyle 1992 170 Heart Rate (b/min) 160 ** 150 - 140 - 130 150 Stroke Volume (ml) 140 - 130 - I *t§ 120 *+ 110 - 100 90

Dehydration and Physiological Effects on Cardiac Output and Blood Flow

20 Cardiac Output (l/min) 19 *+§ 1 18 - No Fluid Small Fluid 17 - Moderate Fluid Large Fluid 16 - 17 - Forearm Blood Flow (ml/100 ml/min) 16 + 15 H 14 13 I 1 12 11 10 0 20 40 60 80 100 120 Time (min) THR + & SV = V Q • · ^ Blood flow (20-22%) · Increase core body temperature and heart rate and a reduced stroke volume Practically · Oxygen delivery · Utilization of energy stores · Time to fatigue Montain and Coyle (1992) No Fluid 304 - Serum Osmolality (mOsmol/kg) Moderate Fluid 300 - Large Fluid HH 296. HI 292. ** 288 H 1 HI I* ** 284. I 280 152 Serum Sodium Concentration 150 - 148. H 146 T *+ 144. (mmol/l) 142. 140 - T 0 20 40 60 80 100 120 Time (min) OH I * H Small Fluid H

Dehydration and Physiological Responses to Exercise in Heat

A B 20. 20 -Hydrated -E-Dehydrated a 18- 18 - a 7- 7- 6.5- 6.5- a 6- a 6- 5.5- 5.5- - 5- 5- 4.5- 4.5- 4 - 4- 3.5- 3.5- 3- 3 a a 9 9 a - -- a 8. 8 7 a 6- 6- Thirst 5 5- 4 4 3 3 2- 2- 1 - 1 Pretrial Loop 1 Loop 2 Loop 3 20 Min posttrial Pretrial Loop 1 Loop 2 Loop 3 20 Min posttrial Time Time a a 7.5- 7.5- 9 a Click on image to zoom 16- 16- 14. 14. 12- 12- 10- 10- · Water deficit on physiological responses to exercise in water outdoor environment · 12 km runs (3 x 4 km loop) 26.5 degrees · Hydrated vs dehydrate in race and submaximal . ^ RPE · ^ thermal sensation · + thirst · Casa et al., (2010) + Rating of Perceived Exertion a a a 7 a

Exercise-Induced Dehydration and Performance

Plasma volume Plasma osmolality 1 Thirst 1 Mood Muscle glycogen use Į CV function î Body temperature 1 RPE - I Impaired endurance performance James et al., (2019)

Dehydration and Performance Factors

• endurance performance
• strength performance
• decrease in skill performance
• cognitive performance
• >2% body mass loss impair endurance performance (Stearns et al., 2009 ; Kenefick et al., 2010; James et al., 2019)

Factors Influencing Dehydration

Factors · Sweat - environment · Clothing worn · Acclimation · Type of exercise - endurance · Logistics - carrying fluid, drink stations · Physiology - GI issues and comfort · Importance of practice

Does Dehydration Really Impair Performance?

1Contrasting literature 320 25 280 Race time (min) 240 200 . 160 120 -10 -5 0 5 Weight change (%) Percentage of runners 20 15 10 5 0 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 Weight change (%) · Relationship between athletic performance and the change in BW during 42 km marathon (2009 Mont Saint-Michel Marathon France) · N = 643 (560 males, 83 females) · Those who finished fastest had the greatest loss in body (Zouhal et al., 2011)

Contrasting Literature on Bodyweight Loss and Running Speed

A 4,5 y = 0.333x - 1.6303 r= 0.65, p<0.05 4,0 Bodyweight Loss (%) 3,5 3,0 2,5 2,0 - 1,5- 11 12 13 14 15 16 17 Running Speed (km/h) B 3,0 y = 0.2039x - 0.9583 r=0.78, p<0.05 2,5- Sweat Rate (L/h) 2,0 - 1,5 - 1,0 - 11 12 13 14 15 16 17 Running Speed (km/h) Rate of Fluid Consumption (mL/h) O 1000 900 y =- 33.589x+860.33 r =- 0.224, p>0.05 800 700 600 500 . 400 300 · · 200 100- 0 - 11 12 13 14 15 16 17 Running Speed (km/h) · TD (384 + 180 ml/h) vs PFI (1,380 ± 320 ml/h) · NO PERFORMANCE BENEFIT · Dion et al.,(2013)

Drinking Behavior of Elite Male Marathon Runners

· Drinking behavior of elite male marathon runners · Temperature 15.3 degrees ± 8.6 and 59% ± 17% relative humidity · 02:06:31 + 00:01:08 average completion time · Total Drink duration 25.5 + 15.0 seconds · Fluid intake 0.55 ± 0.34 l/h · BM loss · 8.8% ± 2.1% TABLE 3. Measured BM Changes During Approximately 30-Minute Exercise Bout in the Heat, Estimated Changes in 5 Athletes, and Observed Changes in 1 Athlete During 42-km Marathon Races Measurements During Approximately 30-Minute Exercise Bout in the Heat Values Estimated for 42-km Marathon Observed Values During 42-km Marathon Race Subject PreBM PostBM DeltaBM Exercise Time BML, kg/ BML, kg BML, % BML, kg/h BML, kg BML, % 1 59.0 57.6 1.4 30.3 2.7 5.8 9.9 2 52.6 51.7 0.9 35.4 1.6 3.5 6.6 2* 52.7 51.7 1.1 39.4 1.6 3.5 6.6 3+ 57.0 53.9 3.2 60.0 3.2 6.7 11.7 3.6 5.7 9.8 4 57.8 56.2 1.5 36.6 3.0 6.3 10.9 4* 57.1 55.0 2.1 61.1 2.2 4.7 8.2 48.4 46.8 1.6 56.7 1.7 3.7 7.5 Mean 54.9 53.3 1.7 45.6 2.3 4.9 8.8 3.6 5.7 9.8 SD 3.8 3.6 0.8 13.1 0.7 1.4 2.1 - *Different exercise bout. +Same athlete as subject 2 in Table 1. ¿Same athlete as subject 9 in Table 1. BML, body mass loss. Duration of Drinking (Observed), Duration of Drinking (Extrapolated), Total Fluid Intake, mL Extrapolated Rate of Fluid Intake, L/h Athens 2004 30 39 2:10:55 19.35 3.7 11.2 506.2 0.23 Berlin 2006 2 20 ± 3 30 ± 13 2:04:26 20.29 21.6 28.8 1299.5 0.63 Berlin 2008 2 12 ± 2 89 ± 12 2:03:59 20.39 20.2 40.5 1829.7 0.89 Berlin 2009 2 16 ± 1 72 ± 8 2:06:08 20.00 17.4 24.3 1097.5 0.52 Dubai 2009 2 16 ±2 54 ± 14 2:05:29 20.10 24.0 38.4 1735.7 0.83 Beijing 2008 3 27 ± 2 52 2:06:32 20.00 12.4 19.6 885.9 0.42 Chicago 2008 First 4 21 ± 3 59 ± 9 2:06:25 20.00 10.5 14.0 631.0 0.30 Chicago 2008 Second 5 21 ± 3 59 ± 9 2:07:37 19.81 45.0 48.8 2204.9 1.04 Chicago 2009 3 0±1 70 ± 5 2:05:41 20.10 10.5 12.0 542.4 0.26 London 2006 6 10 ± 1 84 ± 3 2:06:39 20.00 38.0 50.7 2289.8 1.09 London 2007 7 18 ± 3 55 ± 9 2:07:41 19.72 31.0 31.0 1401.2 0.66 Fukuoka 2009 8 7±1 63 ± 7 2:06:10 20.00 20.5 32.3 1458.2 0.69 New York 2008 9 6 ±1 42 2:08:43 19.63 1.4 1.6 72.8 0.03 Rotterdam 2010 10 9 ±1 2:04:48 20.29 2.7 3.6 164.1 0.08 Marathon Athlete (No.) Temperature, Humidity, % Time, h:min:s Pace, km/h S S

Practice and Performance

• 1 Ability to tolerate
• ^ Power to weight ratio · Beis et al.,(2012) -