;ecture 3, Metabolism

Question 1

ATP-PCr Energy System

Answer 1

• high-intensity exercise of short duration (<10 s) requires immediate energy from intramuscular ATP and PCr (100 m dash)
• each kg of skeletal muscle contains 3 to 8 mmol of ATP and 4 to 5 times more PCr
• although all movements require high-energy phosphates as an energy source, some rely almost exclusively on this energy transfer system
• anaerobic system (ATP-PCr and glycolytic system) that allow us to provide ATP without sufficient oxygen (fastest ways to provide ATP but only short duration)

Question 2

Short-Term Glycolytic (Lactate-Forming) Energy System (fast glycolysis)

Answer 2

• energy to phosphorylate ADP during intense, short-duration exercise comes mainly from stored muscle glycogen breakdown via anaerobic glycolysis with resulting lactate formation
• rapid and large accumulation of blood lactate occurs during maximal exercise of 60 to 180 s
• decreasing exercise intensity to extend duration depresses lactate accumulation rate and final blood lactate levels
• we have exhausted our phosphocreatine supplies but we need rapid ATP generation as there is a buildup of ADP and do not have oxygen to do it (taking glucose or glycogen, getting only a small amount of ATP from it and taking most of the energy from the molecule converting it to lactate which can be used later

Question 3

Long-Term Energy: The Aerobic System

Answer 3

• aerobic metabolism provides nearly all of the energy transfer when intense exercise continues beyond several minutes
• oxygen uptake during exercise initially rises exponentially before it plateaus, and then remains in steady-rate for the duration of effort
• steady-rate aerobic metabolism reflects a balance between energy required by working muscles and ATP production in aerobic reactions
  ◦ no appreciable blood lactate accumulates under steady-rate metabolic conditions
• as exercise intensity increases our capacity to provide only anaerobic system diminishes quite quickly so for longer duration exercise almost all the ATP we produce is from the aerobic system (beyond a few minutes)
• steady-state: there is a balance between ATP requirements of the muscle and ATP that is produced by aerobic metabolism (that does not mean we cannot produce any anaerobically it just means that all that is being produced is being consumed at the same time) - we need a flat oxygen consumption and we need to not be using any anaerobic metabolism that cannot be metabolize the products at the same time
• in steady-state we do not see accumulation of lactate in blood or gradual increases of oxygen consumption

Question 4

Steady-State (rate) Exercise

Answer 4

ATP demands are equal to aerobic ATP production (do not usually have this during very high intensity exercise as we are constantly accumulating lactate)

Question 5

VO2max

Answer 5

the maximal amount of oxygen the body can consume in 1 minute; occurs when an increase in ATP demands does not increase aerobic ATP production

Question 6

Lactate threshold

Answer 6

the exercise intensity when lactate begins to accumulate in the blood

Question 7

Oxygen deficit

Answer 7

how much less oxygen was actually consumed during exercise than if ATP demands when completely met with aerobic ATP production

Question 8

Excusive post-exercise oxygen consumption (EPOC)

Answer 8

how much more oxygen was consumed during recovery than is theoretically required during rest

Question 9

Examples of activities which primarily use

Answer 9

ATP-PCr
- olympic mens 100m sprint, 40 yard dash, power lifting 1 rep max, high jump, golf swing, shotput (anywhere we are working maximally under 10s)

aerobic-CHO
- mile swim, 3-5k and even a 10k at the olympic level (things you are doing for half an hour at a maximal rate)

short-term glycolytic
- 200-400m sprint (olympic), shift in hockey

aerobic-fat
- iron man event, ski touring all day, anything that is long duration but within your comfort zone (not too hard but doing it for a long time you will be burning mostly fat)

Question 10

Lactate Accumulation

Answer 10

blood lactate does not accumulate at all exercise levels
- during light and moderate exercise (<50% aerobic capacity), blood lactate production equals lactate disappearance, with oxygen-consuming reactions adequately meeting exercise energy demands
- for healthy, untrained persons, blood lactate begins to accumulate and rise in an exponential fashion at about 50 to 55% of maximal capacity for aerobic metabolism
my notes:
- we are always using all of the energy systems at any given time
- we can make lactate at lower energy and do not need to be doing a 400m sprint for example (we make lactate sitting around, doing a light jog)
- make more lactate then we can use as a fuel when we reach a certain exercise level (make more lactate than we can convert back into pyruvate, to make ATP and back to glucose)
- at low intensity exercise you are metabolizing lactate more than you are producing it
- at higher intensity exercise even if we are below our maximal aerobic capacity we are going to start making lactate at a higher rate than we can metabolize (more muscle fibres have to produce lactate at a higher rate so we see an accumulation of lactate in the blood)]