KNES 373 - Final Exam Review

lectures 13 and 14 (VO2max and exercise thresholds/domains), lecture 11 (anaerobic metabolism)

What is VO_2max?

quantitative measure of an individual’s capacity for aerobic ATP resynthesis (max rate of oxygen uptake)

aka: maximal oxygen uptake, maximal aerobic power, aerobic capacity

What are the 3 different exercise tests used to measure VO_2max?

• ramp incremental (continuously increasing intensity)

• step incremental (intensity increases in steps)

• constant intensity (intensity stays the same)

When matched for training level, normalizing VO_2max by lean body mass eliminates _______________ differences in VO_2max.

sex-based differences

A high VO_2max is necessary but not _____________ for success in events that are primarily aerobic.

sufficient

How much does VO_2max decline per decade of age?

8% decline per decade in males and females

decline starts around age 30

decline can be slowed with training, but not eliminated

Ventilation shows a _____________ relationship during the VO_2max test. What are the 2 important thresholds?

curvilinear, gas exchange threshold (GET) + respiratory compensation point (RCP)

Why are ramp incremental tests performed?

• to determine exercise capacity (VO_2max)

• to identify cardiorespiratory response thresholds

What occurs in phase I of a ramp incremental test (RIT)?

• linear increase in O₂ consumption

• linear increase in CO₂ production

• linear increase in V_E

• metabolic steady state (oxygen demand matches oxygen supply)

• blood lactate/H⁺ are consistent (2 mmol/L)

The _____ or ______ is the upper boundary of the moderate-intensity domain, in which VO₂ reaches a steady-state within ______ minutes and blood lactate remains around resting values.

GET (gas exchange ratio), LT1 (lactate threshold 1), 2-3

Why does blood lactate not increase below the GET?

• the demand for ATP can be met by aerobic glycolysis and glycogenolysis

• rate of pyruvate production is approximately equal to the uptake + oxidation of pyruvate, so that conversion of pyruvate to lactate is low

• after a few minutes, fat oxidation will be the predominant energy system

What occurs in phase II of an RIT?

• linear increase in O₂ consumption

• nonlinear increase in CO₂ production

• V_E increases at a faster rate in relation to increased work load or VO₂

• steady state (oxygen demand matches oxygen supply)

• BL/H⁺ are consistent but at a higher level

• BL/H⁺ production and clearance is still at equilibrium

At the gas exchange threshold (GET), CO₂ and H⁺ are _____________________________, causing an increase in CO₂ production. The activation of the _____________________ increases the rate of H⁺ production.

buffered by bicarbonate, glycolytic pathway

Anaerobic glycolysis is activated in the __________ domain.

heavy

What is MLSS?

maximum lactate steady state, another name for RCP

critical intensity of exercise, the highest metabolic rate at which steady-state responses in VO₂ and blood lactate are achievable

How long does it take to reach steady-state in the heavy intensity domain?

10-15 minutes

In the heavy intensity domain, there is an increase in the rate of ____________ production, which exceeds the rate of uptake and oxidation, and there is an increase in _____________ production, resulting in greater _____________ concentration.

pyruvate, lactate, blood lactate

In the heavy intensity domain, although the metabolic demand and blood lactate concentration are elevated, ______________ is still achieved because the physiological buffering systems (_____________, ______________, ______________, _____________) are able to minimize the metabolic disturbance.

steady-state, bicarbonate buffering system, hemoglobin, proteins, phosphates

What occurs in phase III of a RIT?

• linear increase in O₂ consumption

• nonlinear increase in CO₂ production

• hyperventilation can not compensate the rise in H+

• no metabolic stability (steady state)

• BL/H+ production exceeds the clearance

What happens to ventilation beyond the RCP?

• nonlinear increase in ventilation compared to CO₂ production

• to compensate for the decrease in pH, V_E increases out of proportion to V_CO2

• hyperventilation can not compensate for the rise in H⁺

In the severe intensity domain, muscle metabolic responses to the high ATP demand result in a ________ rate of glycolysis which exceeds the ability of the _____________ to accept the increased production of pyruvate and the capacity of the system to buffer the increased ________ associated with the conversion of the lactate to pyruvate. What does this result in?

faster, mitochondria, H⁺, results in failure to achieve steady-state

What are the ranges of blood lactate concentration for each domain?

moderate: < 2 mmol/L

heavy: 2-4 mmol/L

severe: > 4 mmol/L

Why is exercise performed above the MLSS considered unsustainable?

a net anaerobic contribution to ATP resynthesis is required, signified by an unstable and increasing blood lactate

The power output associated with MLSS produces a VO2 equivalent to the ________.

RCP

The ramp-incremental test has become a gold-standard protocol to quantify _________ and _______________.

VO2 max, gas-exchange thresholds (GET, RCP)

What is mean response time?

in response to ramp exercise, O2 uptake at the mouth increases linearly with power output, however VO2 shows a delayed increase in relation to power output at the very beginning of the ramp

MRT stems from transit delay in physiological responses (neural and humoral adjustments) that need to occur at the beginning of the exercise to meet the demand of muscle VO2

When prescribing exercise in the moderate domain, the power output difference produced by the MRT should be ____________ from the ramp power output; otherwise what?

subtracted, otherwise the exercise intensity will be underestimated

In addition to the power output difference produced by the MRT, the _______________ should also be considered for exercise prescribed in the heavy and severe domains.

slow component

_______ alone should be applied in the moderate domain; both __________ and __________ should be applied for the heavy and severe intensities.

MRT, MRT, VO2 slow components

There is no dissociation (drift upwards/slow component) of O2 uptake for a given power output during constant exercise vs. a ramp incremental test in the ___________ intensity domain (below _____).

moderate, GET

What are the reasons for the slow component (dissociation of VO2) during constant load exercise vs. RIT?

type I muscle fibers fatigue, leading to recruitment of type II muscle fibers which are less efficient and consume more O2

What is the dissociation (slow component) of VO2 for each exercise intensity domain (including extreme)?

• moderate

  • no dissociation

• heavy

  • VO2 takes longer to stabilize + reaches values that are greater than predicted because of dissociation of VO2

• severe

  • VO2 increases to VO2 max because of dissociation of VO2

• extreme

  • exhaustion occurs before VO2 reaches VO2max

Why are exercise thresholds important?

• can be used to accurately prescribe exercise

• predicts exercise performance (determine the feasibility of a given exercise task)

How long can each exercise domain be tolerated?

• moderate → > 2 hours

• heavy → 45 min to < 2 hours

• severe → seconds to 45 min

Thresholds are highly individual. What range of percentages of VO2max correspond to each threshold? This indicates that even at the same percentage of VO2max, individuals are not experiencing the same ______________.

GET/LT → 40-80% of VO2max

RCP (MLSS) → 65-95% of VO2max

metabolic stress

Regardless of fast (steep) or slow (shallow) ramps in an RIT, thresholds will occur at the same _________, but thresholds will not occur at the same _____________, and peak _____________ will be different between fast and slow ramps. The _________ ramp will reach a higher peak ___________ than the other ramp.

VO2, power output, power output, fast/steep

_______________ depends on the slope of the RIT. In a slow RIT, the power outputs at the GET and RCP thresholds will be ____________ than the power outputs at those thresholds in a fast RIT.

Power output, lower

What is critical power?

the maximum rate of work that an athlete can sustain for a long time without fatigue, considered to represent the greatest metabolic rate that results in wholly oxidative energy provision

derived from multiple time to task failure exercise visits

the asymptote of the power-duration relatioship

What is W’?

the amount of anaerobic work that can be performed above critical power (predicts time to exhaustion in the severe-intensity domain)

does not represent a finite amount of anaerobic energy available, it provides a measure of exercise tolerance for intensities that are dependent on anaerobic metabolism

Skeletal muscle mitochondrial protein content and slow twitch fiber proportion are strongly correlated with greater _____________.

critical power

What are the components of the glycolytic system (anaerobic metabolism)?

• glycogenolysis

• glycolysis

• lactate production

Which macronutrient is the only one that can generate ATP both anaerobically and aerobically?

carbohydrates

From where are carbohydrates available during exercise?

• blood

• muscle

• liver (to muscle via blood)

• ingested (from digestion to muscle via blood)

How does glucose enter a muscle cell?

GLUT 4 (glucose transporter 4)

• transport protein (NOT an enzyme)

• specific to muscle cells

GLUT 4 uses _____________ in which the glucose molecules follow a concentration gradient, and are sensitive to which hormone?

facilitated diffusion, sensitive to insulin

How does the immediate system function?

as soon as muscle contraction starts:

• stored ATP is broken down into ADP + P_i

• increased Ca²⁺ and byproducts (ADP, P_i, H⁺) are formed and activate CK (creatine kinase)

• CK accelerates breakdown of PCR to donate a P to ADP to create ATP

What are the 5 enzymes involved in anaerobic glycolysis?

• hexokinase (HK)

• phosphofructokinase (PFK)

• lactate dehydrogenase (LDH)

• glycogen phosphorylase (PHOS)

• glycogen synthase

If you are at rest, glucose will be converted to ________________. If you are exercising at a low intensity, glucose will be converted to ______________ in the __________________ and then into ______________ in the ________________. If you are exercising at a high intensity, glucose will be converted to ___________ from _____________ (in the ___________).

glycogen, pyruvate, cytosol, acetyl CoA, mitochondria, lactate, pyruvate, cytosol

Explain the process of anaerobic glycolysis.

1. insulin binds to insulin receptor, signals GLUT 4 inside the cell

2. GLUT 4 moves to the cell membrane, glucose moves into the cell (from blood)

3. hexokinase converts glucose to glucose-6-phosphate (G6P) so that it can’t leave the cell (uses 1 ATP)

4. 2 paths:

at rest: G6P converted to G1P by phosphoglucomutase), G1P converted to glycogen by glycogen synthase

exercise: G6P converted to fructose-1,6-phosphate (uses 1 ATP)

• fructose-1,6-phosphate is converted to 2 pyruvates by PFK (makes 4 ATP (2 per pyruvate), 1 NADH)

  • low intensity exercise: pyruvate enters mitochondria to produce energy

  • high intensity exercise: pyruvate is converted to 2 lactate by LDH (lactate dehydrogenase), NADH is oxidized to NAD+

• glycogen is broken down into G1P by PHOS (glycogen phosphorylase), G1P converted to G6P by phosphoglucomutase

What is the net ATP output from glucose and from glycogen?

glucose → uses 2 ATP, produces 4 ATP, net: 2 ATP

glycogen → uses 1 ATP, produces 4 ATP, net 3 ATP

What does hexokinase do?

converts glucose to glucose-6-phosphate (G6P, P from ATP attaches to glucose)

What are the 2 fates of G6P?

1) undergoes glycolysis

2) stored as glycogen

Phosphofructokinase is a ___________ enzyme that is activated and inhibited by what?

rate-limiting

activated by: ADP, AMP, P_i, G6P

inhibited by: ATP, H⁺

Anaerobic glycolysis yields ______ ATP (net). It also yields ______ NADH, which is __________by lactate dehydrogenase (LDH) to form NAD+.

2, 2, oxidized

What is glycogenolysis? What is happening and where? What enzyme catalyzes this reaction?

• breakdown of glycogen into glucose-1-phosphate (G1P), end goal is glucose

• occurs in the sarcoplasm (outside of mitochondria)

• catalyzed by glycogen phosphorylase (PHOS)

Glycogen phosphorylase (PHOS) is a ______________ enzyme. What activates and inhibits its activity?

rate-limiting

activated by: Ca²⁺, AMP, P_i, epinephrine

inhibited by: ATP, H⁺, G6P

What is the ATP yield for glycogenolysis?

3 ATP (net)

requires 1 ATP

produces 4 ATP

What is McArdle disease?

mutation in gene that provides instructions for making the enzyme glycogen phosphorylase which leads to an inability to break down glycogen effectively

Differentiate between the 2 types of glycolysis in regards to need for oxygen, speed, ATP production and the product.

What does lactate dehydrogenase (LDH) do?

convert between pyruvate and lactate

Lactate is formed when ____________ and ______________ accumulate, because it signals that the mitochondria don’t have the capacity to accept pyruvate for the TCA cycle. Conversion of lactate to pyruvate increases ________ to continue the process of anaerobic glycolysis.

pyruvate, NADH + H⁺, NAD⁺

How is lactate a buffer for H+?

lactate consumes H+ during its production from pyruvate

How does exercise intensity affect lactate production?

higher intensity → more lactate production (exponential increase)

What is the fate of lactate?

converted back into glucose in the liver, converted back into pyruvate to be oxidized in the TCA cycle, fuel source for heart and brain

Which energy system increases its contribution during 30s all-out cycling exercise? Which energy systems decrease their contribution?

aerobic glycolysis (oxidative phosphorylation)

anaerobic glycolysis, PCR