Kines 350: Exam 5

what is an acid?

can liberate an H+

• increases pH

what is a base?

can combine with H+

• decreases pH

what is pH?

the potential or “power” of H+

• neg log of H+

• if 1x change in pH there is a 10x change in concentration

normal blood pH range

• normal: 7.4 ± 0.05

• acidosis: pH < 7.4

• alkalosis: > 7.4

what is OBLA?

onset of blood lactate

• 4mmol/L lactate

low pH ______ Hgb affinity for O2

reduces

what is the origin of acid-base disturbances?

origin = the primary effect

• respiratory or metabolic

• Compensation will correct the disturbance (the other steps in)

what is VT2?

defines the severe intensity workout

• denoted by hyperventilation (do to accumulation of acid in muscle → overventilation)

what senses the low oxygen, especially during high altitude environments?

peripheral chemoreceptors (like in carotid)

what is metabolic acidosis?

gaining acid through metabolic needs

• long term starvation: ketone body accumulation

• uncontrolled diabetes: diabetic ketoacidosis (ketone bodies)

• high intensity exercise

what is metabolic alkalosis?

loss of acids from body

• severe vomiting

• kidney disease

• prolonged hyperventilation at altitude

exrecise is a condition of _____-osis

acidosis

what are the sources of H+ during exercise?

volatile acids

• production of CO2 (results in H+)

organic acids

what types of activities produce acid accumulation?

• lasting greater/= 46 seconds

• effort: at 100% increases risk, all-out sprint

how does acid-base status effect exercise?

• inhibits enzymes in glycolysis, krebs, and oxphos

how are intracellular buffers buffered by extracellular systems

• bicarbonate buffering system

• Na+ - H+ exchanger and Lactate transporters; MCT

• shift protons out of muscles

what is the henderson-hasselbach equation?

the buffering system for H+ ions, and the production of CO2

what is respiratory acidosis?

pH is low

• high PCO2

• ventilation: low

what is respiratory alkalosis?

the pH is too high

• low PCO2

• ventilation: high

what is metabolic acidosis?

pH is low

• PCO2 is low: because protons coming form somewhere else stimulate ventilation

• ventilation: compensates for acidosis (increases)

what is metabolic alkalosis?

high pH

• PCO2: high

• ventilation: low

how do the kidneys compensate for acidosis?

excess protons are secreted into the proximal convoluted tubule from blood

• urinary protons combin with HCO3

• CO2 is reabsorbed, ultimately increasing blood HCO3

what are the sources of H+ ions during exercise?

volatile acids

• carb, fat, and protein metabolism, and the production of CO2 end product

organic acids

• accumulation of products (i.e., glycolysis and lipid metabolism)

what type of acid is the biomarker for exercise acidosis?

organic acid

activities lasting ______ seconds can produce significant amounts of

≥45s

how does the acid-base balance impact performance?

increased [H+]

• inhibits enzymes for glycolysis, krebs cycle, and oxphos

• impairs muscle contractile process by competing with Ca2+ for troponin binding sites

what are the three lines of defense helping to maintain the acid-base balance

1. intracellular buffer systems

• rapid (seconds)

1. blood buffer systems (cardiorespiratory compensation)

• minutes (seconds-min)

1. renal

• hours-days

what are buffers, and what are the main intracellular and blood buffers?

Buffers release H+ ions when pH is high and accept H+ when pH is low

• intracellular

  • proteins (carnosine) and bicarbonate

• blood (extracellular)

  • bicarbonate and phosphates

how does fiber type impact intracellular buffer capacity

fast fibers (type II) possess a higher buffering capacity than slow (type I)

how does exercise training impact buffering capacity?

high intensity training improves buffer capacity in both trained and untrained

• increases in both carnosine and hydrogen ion transporters

how are intracellular protons buffered by extracellular systems?

bacarb buffering

• tansported by Na+ -H+ exchanger (NHE) and lactate transporters (monocarboxylate transporters; MCT)

• shifts protons between intracellular and interstitial spaces

how does ventilation maintain acid-base balance

bicarbonate mostly

• when [H+] increases → pH decreases and reaction moves left (more CO2)

• ↑ [H+] stimulates central chemoreceptors to ↑ ventilation

• ↑ CO2 released from longs, ↑ pH

what does H+ production during exercise depend on?

• intensity

• amount of muscle mass involved

• duration

blood pH _____ with increasing intensity of exercise

declines

muscle pH ____ more dramatically than blood pH

declines

• muscles have lower buffering capacity

how do the kidneys maintain the acid-base balance?

• HCO3 is secreted by the glomeruli (cannot be directly reabsorbed)

  • converts to CO2 + H2O, then can be absorbed

what occurs in the kidney during blood acidosis

• excess protons are secreted into the PCT

• urinary protons combine with HCO3

• CO2 is reabsorbed, increasing blood HCO3

what happens in the kidney during blood alkalosis

• excess HCO3 is secreted, less absorbed

• restores in about 2-3 days

What is the combined gas law?

PV = nRT

• described the relationship between temperature, pressure, volume and moles

what is daltons law?

total pressure is the sum of partial pressure

• PP = concentration x total pressure

• defines diffusion gradient for gas exchange

• bound gases do not participate

why are partial pressures important in physiology

PP is the fraction of total (barometric) pressure that a gas exerts

• PP = Fgas x Pbar

what is barometric pressure?

the sum of all partial pressures

PO₂ + PCO₂ + Pn₂ = P_bar

what is the relationship with altitude and oxygen?

the percentage of O₂ does not change, but since the air is thinner, the partial pressure is less

what is hyperoxic and hypoxic?

hyperoxic: Higher PO2 than sea level

• >21% O₂

hypoxic: lower PO2 than sea level

• hypoxic hypoxia: breathing low FiO₂ (fraction of inspired oxygen) gas at sea level

• hypobaric hypoxia: breathing air while altitude

• <21% O₂

what are the ranges of altitude?

• Adaptive range: 5000-11,500

• Maladaptive range: 11,500 - 18,000

• Death zone: >18,000

• If hypoxia limits training, performance will suffer

what are the atmospheric conditions at high altitude?

lower atmospheric pressure

• lower air density

• lower PiO2

• lower PH2O

lower air temperature

• impacts thermoregulation

• lower PH20 (dehydration)

more solar radiation

in general, what types of events benefit from atmospheric training?

sprinting

What is the relationship between VO_2max and altitude

decreased at higher altitudes

• about 1% decrease every 100m

low altitudes:

• Decreased VO_2max results from lower oxygen extraction

moderate altitudes:

• decreased arterial PO2 contributes to reductions in VO_2max

higher elevations:

• max cardiac output is less

how does altitude impact submaximal exercise?

• higher HR and CO

• lower oxygen content of arterial blood

• higher ventilation (stimulated by peripheral chemoreceptors)

• increased lactic acid concentration in submaximal exercise

what is the lactate paradox?

with higher altitude, the lower peak lactate

a transient phenomenon

• upon exposure: higher HR, ventilation, and lactate during exercise

• after 4+ weeks: glycolytic capacity recovers, lactate response recovers

likely people are just failing and quitting, they are at lower workload

what are the strategies to compete at altitude?

get in, get out

• arrive ASAP before competing and leave ASAP

acclimate for at least 2 wks, preferably 6

• reduce intensity to 60-70% normal

• work up to full intensity over 2 weeks

• may be incorporated in taper

what are the adaptations for residents at altitude?

have complete adaptations in arterial O₂ and VO_2max (usually have one or the other

• produce more RBC: higher hemoglobin concentration (counters desaturation by low PO₂)

• Greater oxygen saturation: greater pulmonary blood flow (increased ventilation)

What is acclimation?

prolonged exposure

• blood adaptations:

• erythropoietin stimulates RBC production

• muscle:

• decrease fiber areas (20-25%)

• decrease krebs cycle enzymes (20-50%)

• cardiorespiratory:

• chronic exposure >2,500m/8,000 generally does not increase VO_2max

• metabolic

• shift toward CHO metabolism

what is HIF (hypoxia-inducible factor) pathways?

• hypoxia is main stimulus for HIF

• it binds to a protein

• portion of DNA transcription activated

• leads to genes beneficial for endurance exercise

  • erythropoiesis

  • angiogenesis

  • more glycolytic enzymes

  • more vasodilation

  • but inhibits mTOR

what is the optimal hypoxic prescription?

frequency: at least 22hr/day

intensity: altitude 2300±200m

time: 4wks

type: consider either method to create hypoxia and maintaining high quality exercise training

• live high train low

what is the main takeaway of the live high, train low study?

that hypoxia does seem to have a little positive impact

• But likely that elite athletes training with elite athletes pushed each other for improvement

what are the mechanisms for performance in hypoxic environments

blood

• increased RBC (increased O2 transport)

non-blood (muscle)

• increased efficiency of mitochondrial metabolism (decrease O2 used at fixed rate)

what are the challenges of high altitude climbing?

• dont have particularly high VO_2max

• altitude sickness: loss of appetite, weight loss reduced type I and type II muscle fiber size

• successful climbers: great capacity for hyperventilation (increases alveolar PO2)

acid-base considerations of altitude acclimation

• early exposure stimulates peripheral chemoreceptors, causes hyperventilation

  • increased ventilation and P_AO₂

  • increased P_ACO₂

• Respiratory alkalosis develops in minutes (from hyperventilation)

  • reduces stimulation of central chemoreceptors

  • may contribute to mountain sickness

• over days: urinary excretion of excess HCO3 helps restore acid base status

what are the medical problems with living and working at altitiude?

• polycythemia: excessive EPO response, increases blood viscosity

• acute mountain sickness (ASM)

• high altitude pulmonary edema: accumulation of fluid in lungs

• high altitude cerebral edema (HACE): accumulation of fluid in cranial cavity

what is acute mountain sickness (AMS)

headaches, loss of appetite, nausea, vomiting

cheyne-stokes breathing: sleep disturbances, CO2 accumulation (periodic)

• treated: DESCEND ASAP

golden rules of altitude sickness

rule 1:

• if you are ill at altitude, your symptoms are altitude sickness otherwise

rule 2:

• if you have symptoms, do not go higher

rule 3:

• if you are feeling ill or getting worse, or cannot walk heel to toe in a straight line, or have SOB at rest, descend

rule 4:

• person with altitude sickness should always be accompianied

what are homeotherms?

we as humans can maintain a constant core temperature

• about 37 C

• < 34 and > 45 BAD

what is the thermal gradient

ideal gradient is about 4 C

• distal portions cooler than core temperature

what is the heat balance equation

loss/gain = metabolism ± conduction ± evaporation ± convection ± radiation

• can be modeled to determine the magnitude of gain or loss

what is heat production by metabolism

voluntary

• exercise

involuntary

• shivering

• thyroxine

• catecholamines

conduction mechanism of heat gain and loss

transfer of body heat by direct contact

convection mechanism of heat gain and loss

transfer of heat by motion of molecules at the surface of the skin

• disruption of boundary layer

radiation mechanism of heat gain and loss

infrared emission to or from a body (like radiating heat)

• primary mechanisms for heat loss at rest

evaporation mechanism of heat gain and loss

heat lost with water conversion from liquid to vapor

• primary avenue of heat loss during exercise

• biggest in heat loss

how does evaporation and condensation regulate body heat?

The conversion of water (sweat) from liquid to gas

• requires a pressure gradient between skin and air (not wet air)

• Evaporation rate depends on:

  • temperature and relative humidity

  • convective currents around the body

  • SA of skin exposed

  • Responsible for more than 60% of heat loss

what modes can you expect to see heat losses?

• conduction: heat loss due to contact with another surface

• convection: heat transferred to air or water

• radiation: biggest for at rest

how does body heat balance during graded exercise?

an increase in body temperature is related to exercise intensity

mechanisms of heat loss

• evaporation:

• convection and radiation

what are the thermal events during graded exercise?

as exercise intensity increases

• heat production increases

• linear increase in body temperature

• higher net heat loss

as ambient temperature increases

• heat production is constant

• lower convective and radiant heat loss

• higher evaporative loss

as humidity increases

• heat production remains constant

• similar convective and radiant heat loss

• lower evaporative heat loss