Lecture 12 - Limitations To Exercise Flashcards
Define VO2 max
The maximum rate at which the body can effectively use oxygen during exercise, used as a way of measuring a person’s individual aerobic capacity.
What is the respiratory quotient?
VCO2/VO2
V is rate of consumption/production per minute
When is rate of oxygen/carbon dioxide exchange not the same as usage/release at tissues?(3)
Hyperventilation (excess CO2)
Exhaustive activity (increase in CO2 due to presence of H2CO3 resulting from lactate buffering)
Gluconeogenesis (making glucose from non carb precursors, especially by liver/kidneys using aminos from proteins, glycerol from fats or lactate from muscles during anaerobic glycolysis)
Define RQ vs RER
RQ - indicator of substrate use, can’t exceed 1
RER - respiratory exchange ratio which reflects exchange of CO2 and O2 and can exceed 1, especially during strenuous exercise
Contrast submaximal activity and maximal activity
Metabolic rate * with exercise *
Submaximal - heart rate is 50-80% of maximum, VO2 max not reached
Maximal - VO2 max reached
Increases; intensity
What are the two deviations to submaximal activity?
1) slow component of VO2 uptake kinetics - at high output, VO2 continues to increase and there’s more type 2 recruitment which is less efficient. If you exercise above lactate threshold, there’s an increase in O2 uptake as requirement greater. Element of using more oxygen than needed
2) VO2 drift - upward drift during prolonged submaximal activity, possibly due to increase in ventilation and catecholamines e.g adrenaline.
At maximal activity, what happens to oxygen consumption?
It no longer increases with an increase in intensity
VO2 max * after 8-12 weeks of *
More * allows athlete to compete at ** of **
Plateaus; training
Training; higher percentage; VO2 max
How do you measure anaerobic contribution to exercise?
1) EPOC (excess post exercise oxygen consumption)
2) Lactate threshold
3) Economy of effort
Define lactate threshold
The max effort or intensity an athlete can maintain for an extended time period with little or no increase in lactate
Point when blood lactate production exceeds the body’s ability to clear lactate
What are the limits to VO2 max?
1) central physiological functions - pulmonary diffusion, cardiac output and blood oxygen carrying capability (volume and flow)
2) Peripheral physiological functions - muscle diffusion capacity, mitochondria enzyme levels and capillary density
Define EPOC
Amount of oxygen required to restore your body to homeostasis post exercise
What are the components of EPOC?
Reoxygenation of blood
Replenishment of energy stores (ATP-PCr, glycogen, lactate clearing)
Decrease in circulatory hormones (adrenaline/NA)
Decrease in body temperature
Decrease in heat rate and ventilation to clear carbon dioxide from body
What does oxygen deficit accrue even at low intensity?
Because oxygen needs and supplies differ
Lactate lowers * of blood, and is taken to * for conversion back to * during exercise recovery
When carbonic acid is in blood, what happens when it gets broken into CO2 and water?
pH, liver; pyruvate
CO2 gets removed at the lungs
What are the four key steps of endurance training?
Activity of intensity higher than critical threshold
Sufficient duration
Repeated
Rest-recovery period when adaptations occur
What seven things can endurance training accomplish?
Increases VO2 max Increase muscle fibre sizes and capillaries Increases citric acid cycle enzymes Enhances O2 diffusion into muscle Increase mitochondrial content Increases max O2 delivery Increases plasma volume and CO2 max
Describe acute soreness (strain)
During/after strenuous/novel exercise
Accumulation of metabolic byproducts (H+)
Causes oedema - muscle swelling
Disappears within minutes to hours
Describe delayed onset muscle soreness (DOMS)
24/48h post exercise
Range from stiff to severe
Major cause is eccentric contractions e.g running downhill
NOT caused by increase in blood lactate concentration!!!!!
What is the structural theory of DOMS?
Onset of DOMS parallels onset of enzyme increase; damage indicated by muscle enzymes e.g creative kinase in blood. Also, Z disk myofilament is damaged after eccentric work
What is the inflammation theory of DOMS?
Connection between inflammation and soreness, and WBC’s increase with soreness (WBC’s normal role is defence). Substances released initiate inflammation, and damaged muscle cells attract neutrophils which release attractant chemicals/radicals. The released substances stimulate pain nerves and macrophages remove cell debris
What is the sequence of events in DOMS? (6)
1) high tension in muscle leads to structural damage to muscle and its cell membrane
2) membrane damage disturbs calcium homeostasis in injures fibre, which inhibits cellular respiration
3) calcium activated enzymes that degrade Z disks
4) neutrophils circulate
5) products of macrophage activity and intracellular contents (e.g histamine) accumulate outside cell, which stimulates pain in free nerve endings (worse with eccentric exercise)
6) fluid and electrolytes move into the area, creating oedema
What are the three factors that cause loss of strength due to DOMS?
Loss of contractile protein
Failure in excitation contraction coupling
Physical disruption of muscle
How can you reduce DOMS? (3)
Minimise eccentric work early in training
Start low intensity with gradual increase OR
Start high intensity with exhaustive training so soreness decreases later on instead
DOMS is important to * muscle *
Stimulate; hypertrophy
Compare the two types of muscle cramps
Heat cramps - associated with large sweat/electrolyte losses; treatment is high NA solution, ice and massage
Exercise associated muscle cramps (EAMC) - during/after exercise, fatigue causes altered neuromuscular control and leads to excitation of muscle spindle and inhibition of Golgi tendon organ; relieved by stretching
