KINE 433 exam 3 Woodman

heat & fluid balance, exercise in different environments, clinical populations

what are the components of heat gain? heat loss?

heat gain:

metabolic heat

environmental heat (conduction, convection, radiation)

heat loss:

radiation

conduction

convection

evaporation

What is the goal of heat balance? think of the heat balance equation

equation: M (metabolism) - W (work) ± R (radiation) ± Cv (convection) ± Cd (conduction) - E (evaporation) = S (storage)

the goal is to maintain S=0; keep core body temperature constant

what % does evaporation account for as heat loss during exercise?

evaporation accounts for 80-90% heat loss during exercise

tolerable ranges: what should core temperature be kept at? (°C)- what temp may heat stroke occur? when can death occur?

goal: keep core temp 36-39 °C

heat stroke may occur at 41°C

death can occur at temp of 42°C

where are thermoreceptor located and where do they send feedback to, what does ths area in brain do?

thermoreceptors are located in skin, muscle, spine, and brain

feedback is sent to the hypothalamus

the hypothalamus initiates response (central integrator), acts like a thermostat

what are the steps of actions that take place when hypothalamus initiates response to a rise in core temperature? what is unique about the sympathetic nerves in this response? what aid in heat loss?

1.) core temp rises→ hypothalamus increases SNA

2.) unique sympathetic nerves release ACh causes dilation and activates sweat glands

3.) increases blood flow to skin and sweat production aids in heat loss

what are the sweat glands activated by? what concentration does sweat initially have that is similar to plasma? what elements are reabsorbed in sweat ducts?

the sweat glands are activated by SNS

sweat initially has [electrolyte] similar to plasma

some Na+ and Cl- reabsorbed in sweat ducts

what two stages does sweating occur in?

1.) increase # of active sweat glands

2.) increase output per sweat gland

where is sweat derived from?

sweat is dervied from extracellular water

how is extracellular water replaced?

ECW is replaced by water from plasma and cells

the % body weight loss vs % plasma volume loss; what %BW loss is classified as dehydration?

%BW loss: %Plasma volume loss:

0 0

2 4

4 8

6 12

weight loss x 2= PV loss

2% body weight loss (4% PV loss)

cardiovascular adjustments to heat stress- quotes- wha tis the greatest stress ever imposed on the CV system other than hemorrhage? and these stresses can present life threatening challenges in who?

hyperthermia

highly motivated athletes→ they are physically able and determined to keep going but their body’s temperature rising won’t stop rising and can put them at risk

what are the fundamental problems of heat stress (2)?

1.) skin and muscle compete for BF

2.) BP must be protected

what happens to skin blood flow and muscle blood flow in passive heating?

1.) skin blood flow increases for heat dissipation

2.) muscle blood flow decreases (blood is redirected from muscle to skin)

cascade of CV adjustments when body is HOT

• decrease in central venous pressure

• decrease in central blood volume

• decrease in stroke volume→ decreased preload→ decreased CO, HR must increase to compensate and bring CO back up

• decrease in renal blood flow

• decrease in muscle blood flow

• increase skin blood flow

• increase skin blood volume

What happens to CO? what % of it goes to skin? this is passive heating at rest (not exercise)

CO increases (even though VO2 is not increasing)

60% of CO goes to skin (cutaneous circulation)

what are four things that happen when one exercises in heat? (competition of BF, VR and SV, HR, COmax)

1.) skin and muscle compete for BF

2.) decrease in venous return reduces SV

3.) HR increases to attempt to maintain CO

4.) COmax falls at time of highest demand (cold: 20 L/min; hot: 17 L/min)

heat disorders: what causes heat cramps, heat exhaustion, and heat stroke?

heat cramps: due to loss of sodium and water→ dehydrated

heat exhaustion: due to decrease in skin blood flow (chills, goose bumps)

heat stroke: sweating stops (core temp increases)

why will an athlete eat a banana?

not for electrolyte balance not a major player in sweat; it is gentle on the stomach and digestible carbs used for energy

at what amount of minutes in exercise if fluid intake critical? beyond x minutes?

proper fluid intake is critical for exercise beyond 45 minutes

fluid replacement is not as important for less than this time

the difference of rectal/core temperature when no fluids are replaces vs fluid intake

no fluids: 104 degrees F

fluid intake: 101 degrees F

what does training do with sodium? what are key adaptations for training for heat acclimation (3)- early onset of what, more what is produced, what is the concentration of this?

training protects against sodium (Na+) loss

1.) earlier onset of sweating (sweat glands are activated @ lower core body temp)

2.) more sweat is produced- more sweat glands

3.) sweat becomes more dilute (not as much Na+ loss)

sweat Na+ (mmol/L) loss in untrained men vs trained men and in untrained women vs trained women… Cl- is also a key player in sweat and also gets reduced

untrained men: 90

trained men: 35

untrained women: 105

trained women: 62

Cl-: 60 untrained men, 30 trained me

98 untrained women, 47 trained women

key adaptations with acclimated vs unacclimated

acclimated

1.) plasma volume increases

2.)skin blood flow improved

3.) core temperature better maintained

• 103 vs 101 degrees F

4.) increased exercise tolerance (can exercise for longer period of time- HR does not increase as much or as quick)

• 75 min vs 90 min

how long does training take?

1.) acclimation occurs rapidly (within 12 days… more days, better acclimated)

2.) acclimation is more effective when training in heat (not just living in heat)

cardiovascular drift- what increases to maintain CO

1.) stroke volume decrease in exercise in the heat due to decreased venous return

2.) Heart rate increases to maintain CO

what is the goal of fluid replacement beverages? what are the four things they should do (hydration, fatigue, performance, heat disorders)?

GOAL: to maintain plasma volume so that CV adjustments and sweating can progress at optimal levels

1.) maintain hydration

2.) reduce fatigue

3.) improve performance

4.) prevent heat disorders

gastric emptying- how long does it take for something to move through the stomach? where is water absorbed?

sports drinks should exit stomach quickly (in order for it to be absorbed)

*note: water is absorbed in the small intestines, not stomach

how does carb (CHO) content affect gastric emptying?

the rate of GE declines as CHO content increases (more glucose/sugar→ stays in stomach for longer)

how does electrolyte concentration affect gastric emptying?

rate of GE declines as [electrolyte] concentration increases

balancing fluid and CHO delivery- what do sports drinks do with fluid and CHO delivery? what % of CHO is optimal if no Na+ is present? ACSM reccomendation for % CHO and % Na+?

1.) sports drinks balance fluid and CHO delivery

2.) 10% of CHO is optimal

3.) ACSM recommends 6-8% CHO and 5% Na+

fluid replacement for cramp-prone athletes- what are heat cramps primarily due to ?

heat crams primarily due to loss of H2O and Na+

mean Na+ (mg/hr) loss is 2715… ideally intake if 1500 mg of Na+ in diet

how can heat cramps be resolved/prevented?

heat cramps can be resolved/prevented with proper fluid AND SALT intake

• amount in Na+ in gatorade is not sufficient… need to supplement with table salt

during activity: 32 oz gatorade- 0.25 tsp (1.5g) up to 1 per hour

recovery from activity: 32 oz gatorade- 0.5 tsp (3 g) one per kg post-exercise body weight deficit (weigh before and after… lost 2 kg→ 64 oz with 1 tsp)

what is the PO2 of arterial blood? why is PAO2(alveoli) > PaO2 (artery) - 2 reasons?

PaO2= 100 mmHg

105>100 (alveoli>artery)

• diffusion is not 100% complete

• some blood bypasses ventilated area of lungs- shunts

what happens to alveolar and arterial PO2 with elevation? what is PAO2 and PaO2 at 14,000 ft? PO2 in venous tissue?

Alveolar and arterial PO2 decline as altitude increases

14,000ft:

PAO2= 46 mmHg

PaO2= 42 mmmHg

venous- 27 mmHg

*sea level- 105, 100, 40

does the % of O2 in air we breathe in change with different elevations? what is the %?

the % of Oxygen in air you breathe in= it is exactly the same at sea level and high elevation; it does not change= 20.93%

what is the barometric pressure Pb (mmHg)= atmospheric pressure at sea level vs mt. everest; is barometric pressure

PO2 declines because barometric pressure is lower at high altitude

• sea level: 760 mmHg

• Mt. Everest: 253 mmHg

% O2 in aire does not change

how does high elevation (460 mmHg atm pressure) impact O2 transport? think of the blood flow from left side of heart→lungs→left side of heart→body

O2 delivery decreases

PaO2 at high altitudes decreases

O2 diffusion gradient of blood to muscle decreases (slows rate of O2 exchange)

what happens to VO2 max in altitude, what is it primarily due to?

VO2 max decreases as altitude increases

due primarily to a decrease in PaO2 (less O2 in blood to deliver to active tissues, decreases O2 uptake and utilization)

in percentage %, how much lower was VO2 max at the summit of Mt. Everest compared to sea level?

VO2 max was 75% lower at summit of mt. Everest (29,000 ft)

how was this discovered? what group of people in 1964 went on the expedition to test this? how long did it take (what month/year); what elevations did they test on? what elevation (ft) did Pete Milgrew collapse at?

Pugh et al. anbd John West (1964) went on expedition and set base camps on mount Everest (15,000 ft+) to perform testing

September 1960- June 1961 (10 month expedition)

19,000, 24,400 ft

Pete Milgrew collapsed at 27,400 ft

submaximal exercise at high altitude- is O2 required the same or different? what happens to perception of effort (sea level summaxial %VO2 max vs 14,000ft)? what happens to time to exhaustion

1.) O2 cost (required) of work is not differnt (2L=2L)

2.) perception of effort increases because at higher VO2 max (50% vs 70%)- work harder at submax

3.) time to exhaustion reduces → exhaust quicker in less time

how does high altitude impact exercise performance? what the first two minutes of exercise? what happens in exercises that last beyond 2 minutes

• no impact on events/exercises less than 2 minutes (because you are using pathways that don’t require O2, Pcr an glycolysis)

• performance declines in events/exercise beyond the 2 minutes: oxidative metabolism- this pathways demands oxygen

how to improve? “living high-training low”- what is this- what elevation is “LO” where and what elevation is living “HI'“- what are three adaptations that occur→ VO2 max increases by what % (male and female), Hb content increases by what %, what happens to the 3000 m time?

train LO= 4100 ft (“low” because it rests below the 5000 ft threshold)- able to train at higher intensity here

live HI= 8100 ft

1.) VO2 max increases by 3% (both men and women)

2.) Hb content increases by 7%

3.) 3000 m time decreased by 6 seconds (faster time!)

what is considered overweight (what % over the recommended weight)? what is obesity and what % body fat is considered for man and women?

overweight: Body weight 10% over recommended weight

Obesity is excess body fat

men: >25%

women: >35%

what % of adults in Texas are obese? is prevalence greater in men or women? what races is it most common in?

• 35% of adults in TX are obese

• prevalence is greater in females → 36.1% females; 35.4% males

• most common in black and hispanic populations

what % of children in TX are obese? what is the national average for children?

Texas: 33%

National: 18%

Importance of education- are educated people more or less likely to be obese? why?

1.) educated people are less likely to be obese

2.) education→ better awareness, access to healthier foods, and better healthcare

what is the cost burden - annual cost in US a year? annual cost in TX/year? projected cost by 2040??

annual cost in US: $190 billion/year

annual cost in TX: $16 billion/year

projection: increase by 39% billion by 2040

by what % does physical activity reduce type II diabetes? heart disease?

physical activity decrease the risk of

• type II diabetes: 58%

• heart disease: 40%

What causes obesity?- 3 key points

1.) obesity results form energy imbalance

2.) excess calories stores as fat

3.) due to many factors

what are the top four risk factors (not really lol)? define what each mean?

1.) genetics: determines predisposition for storing fat

2.) environment: families have similar eating and activity habits

3.) age: hormonal change & decrease in physical activity

4.) socioeconomic: access to education and healthcare

what are the complications? what happens to disease risk as body fat increases? what about depression and social isolation?

• body fat increases→ disease risk increase

• body fat increases→ depression and social isolation increases

what is BMI? why is it commonly used?

BMI (body mass index)- the relationship between body weight and height (kg/g=height²)

it is used and practiced because it is easy, highly standardized, and trackable

what BMI is considered obese? does disease risk increase when BMI increases?

BMI>30 classified as obese

disease risk increases as BMI increases

what is the goal for exercise programs for obese populations? short-term goal (lose what % body wight in 6 months)? what changes need to happen

1.) goal: achieve and maintain healthier weight and decrease disease risk

2.) short-term goal: lose 5-10% of BW in 6 months

3.) should include diet change and exercise

exercise recommendations: gradually build up to how many minutes a day? energy expenditure goal (kcal/session)? what setting of exercise should be encouraged?

1.) gradually build up to 60 min/day

2.) energy expenditure goal: 200-400 kcal/session (expend 250 kcal paired with 250 kcal deficit * 7days/wk= 3500kcal/week … lose ~1lb a week

3.) group exercise should be encouraged (helps physically and socially)

it is a slow process (patience)