metabolic response to exercise

rest to exercise transition to energy demand

• we define energy utilization when its constant and standard

• difference from rest to requirement during running

• not a smooth transition in metabolic demand

• muscle must increase ATP production from that required for standing to running

  • increase in HR and RR as we being ot exercise

  • increase in temp. slowly

    • not during initial transition

  • increase in BP

  • increase in SV → causes an increase in Q (cardiac output)

increasing ATP synthesis

• energy system changers are supported by

  • respiratory changes increasing ventilation

    • increase O2

  • cardiovascular changes

    • increased Q

      • increased devilry of O2

    • vasodilation to working muscle

  • muscle changes

    • increased a release/uptake by SR

    • increase myoglobin shuttling

      • facilities O2 transfer to mm

      • mm protein structure

metabolic transition from rest to exercise

• systemic response increases how we function until reaching steady state

  • utilization of free ATP - only takes a few secs

  • anaerobic lactate and aladctatic

• PCr [] during prolonged exercise

  • does drop to 0 as another system sicks in

• As PCr [] decreases ATP production through PCr hydrolysis decreases

• Glycolysis steps up to pick pu the slack

  • ventilation increases as we continue to use glycolytic system

  • ATP produced through glycolytic origin

  • may be rate liming of not only using glycolysis

  • steady state occurs within 1-4mins

how does glycolysis know to start working

• stimulated by products of PCr system

• ATP, creatine kinase

  • all stimulates glycolysis

O2 defecit

• amount of O2 produced via non aerobic sources

• stead state - reached within 1-4mins

• no fueling

  • ATP production aerobically

• difference between O2 uptake in 1st few minutes of exercise and an equal time period after steady state has been obtained

• lag in oxygen uptake at the beginning of exercise

oxygen deficit and EPOC

• light ot moderate intensity exercise

  • metabolic rate remains constant up to 5mins post exercise even at moderate acitvity

  • oxygen uptake above the level needed to meet demands of standing following exercise

• non steady state high intensity exercise

  • maintained for only 6mins before exhaustion

  • intensity that exceeds VO2max

  • could not meet oxygen requirement for task shown by increased oxygen deficit and VO2 above resting level 14mins after exercise

  • at plateau anaerobic production occurs

EPOC

• Excess post-exercise oxygen copumotion

• elevated O2 uptake (above resting VO2 following exercise

• only 20% of elevated O2 consumption used to “repay” O2 defects and

  • convert lactate to glucose

    • gluconeogensis

  • convert lactate to pyruvate to engage with CAC and ETC in

    • Skeletal muscle

    • heart

    • brain

rapid portion of O2 EPOC

• resynthesis of stored PC and ATP / lactate to pyruvate

• replenishing muscle myoglobin and blood O2 stores (20% of EPOC)

  • resaturation of muscle

slow portion of O2 EPOC

• elevated heart rate nad breathing

  • energy need

• elevated blood temperature

  • metabolic rate

• elevated epinephrine and norepinephrine

  • metabolic rate

• conversion of lattice acid to glucose

• CV and RR responses

  • heart and respiratory muscles maintain O2

  • increased sympathetic system

    • increased epinephrine and norepinephrine

      • increases réponse

• gluconeogensis

  • glucose from non-carbohydrate sources generated in liver

why is O2 consumption so high if it is not exclusively used ot covert lactate ot glucose

• summary of factors thought ot contribute to excess post exercise metabolism

  • glycolysis producing most of the ATP

  • elevated hormones

  • post-exercise elevation of HR and breathing

  • elevated body temperature

  • restoration of muscle and blood oxygen stores

  • lactate conversion to glucose

  • resynthesis of PC in muscle

removal of lactic acid following exercise

• faster return to resting VO2 following cooldown

  • light exercise at 35% VO2 max

• lactate removal is more rapid if continuous light exercise is performed as compared to resting recovery

• light exercise increases oxidation of lactate by the working muscle

removal of lactic acid theories

• classical theory

  • majority of lactic acid converted to glucose in liver

• revent evidence

  • 70% of lactic acid is oxidized by cells

    • used as a substrate by heart, brain and skeletal muscle

    • muscle using glucose producing lactate producing amino acids to structurally support the muscle

    • ability to utilize glucose depends on glucose stores in liver

  • 20% converted to glucose

  • 10% converted to amino acids

• lactic acid is removed more rapidly from the blood if light exercise is performed during recovery

  • optimal intensity is ~30-40% VO2 max

bioenergetics during exercise: intensity and duration

• Wingate sprint exercise

  • ATP turnover rate still not from most powerful tissues at beginning

  • 30s all out sprints based on relative resistance

    • %7kg of bodyweight

  • ration shows more CHO than fasts even during sprint

• Fats vs CHO

  • sustained steady state

    • more bonds takes time ot breakdown

      • once moving energy system takes off

  • plasma glucose is not that high even during 85% of VO2 max

  • requires medullas to be fuelled

    • may be beneficial to increase glycogen stores

    • use more glycogen to produce more glycogen

• upward VO2 drift

  • hot and humid

    • drift upward of oxygen uptake

      • steady state is not maintained in this type of exercise even though work rate is constant

  • >75% VO2 max

    • slow rise in oxygen uptake across time

estimation of fuel utilization during exercise

• respiratory exchange ration (RER or R)

  • R = VCO2/VO2

• R for carbohydrate (glucose)

  • C6H12O6 + 6 O2 → 6 CO2 + 6 H2)

  • R = VCO2/VO2 = 6 CO2/6 O2 = 1.00

• R for fat (palmitic acid)

  • C16H32O2 + 23 O2 → 16 CO2 + 16 H20

  • R = VCO2/VO2 = 16 CO2/23 O2 = 0.70

incremental exercise test

• VO2 max

  • maximal capacity ot transport and utilize O2 during exercise

  • O2 uptake increases systematically with work rate until VO2 max is reached

  • at max an increase in power output does not result in an increase in oxygen uptake

    • physiological ceiling for the ability of the oxygen transport system to deliver O2 to contracting muscles

criteria for VO2 max

1. age predicted HR max

2. blood lactate of 8 mm or higher

3. RER above 1.15