Exercise Physiology Flashcards
What are the 3 metabolic pathways?
phosphocreatine, glycogen, glucose fatty acids and amino acids
What is the phosphocreatine pathway?
ATP breakdown
- ATP <–> ADP + Pi + Energy + H+
- occurs rapidly at exercise onset
ATP resynthesis
- PCr + ADP + H+ <–> ATP + Cr
- Enzyme - Creatine kinase
Short-term, intense exercise
Anaerobic – no oxygen
What is glycolysis?
- provides 90s of muscle energy
- breakdown of glucose/glycogen into pyruvate (with O2) or lactate (without O2)
- 2 phases, energy investment and generation
- net gain of 2ATP from glucose
- net gain of 3ATP from glycogen
What is the aerobic system?
- Oxidation of foodstuffs in the mitochondria to provide energy
- Citric acid cycle (Krebs cycle)
- Electron transport chain
- Aerobic metabolism can last indefinitely
Compare usage of the different systems
~100% ATP-CP
- 100m sprint, weight lifting
ATP-CP/anaerobic glycolysis
- 200-400m sprint, basketball
Anaerobic glycolysis/aerobic
- Middle distance running
Aerobic
- Marathon, road cycling
Explain pulmonary ventilation and oxygen consumption
Oxygen consumption for a young male is ~ 0.25 L/min
- Can increase ~ 20 fold between resting and maximal intensity
Pulmonary ventilation at maximal exercise = 100-110 L/min
- Maximal capacity = 150-170 L/min
Provides extra ventilation during
- High altitudes
- Exercise in hot/humid environments
- Abnormalities in the respiratory system
What is VO2 max
- VO2 max is the rate of oxygen usage under maximal aerobic metabolism
- Oxygen uptake increases linearly until maximal oxygen uptake (VO2 max) is reached
- VO2 max occurs when pulmonary ventilation at 60-70%
- VO2 max is the ‘Physiological ceiling’ for delivery of oxygen to muscle
- Affected by genetics and training
- Physiological factors influencing VO2 max
- Maximum ability of cardiorespiratory system to deliver oxygen to the muscle
- Ability of muscles to use oxygen and produce ATP aerobically
What is oxygen diffusing capacity?
- rate at which oxygen can diffuse from pulmonary alveoli into the blood
- measured in mL of oxygen that diffuses each min for each mL of mercury difference between partial pressure of oxygen in alveoli and pulmonary capillaries
What is the relationship between muscle blood flow and exercise?
- blood flow inc is as important as dec
- contractile process temporarily dec muscle blood flow due to compression of intramuscular blood vessels
- blood flow to muscles inc markedly during exercise
What is the relationship between work, cardiac output and oxygen consumption
cardiac output = heart rate x stroke volume
- stroke vol is amount of blood pumped per heartbeat
- during exercise CO is increased by both HR and Sv
What is heart hypertrophy?
- Marathoners and endurance athletes can achieve maximal cardiac outputs that are ~40% greater than untrained persons.
- Heart mass and heart chambers enlarge by ~40%.
- Increase in heart-pumping effectiveness is the key.
Explain the cardiac system as a limiting factor
- cardiac output is 90% the max a person can achieve during exercise
- pulmonary system 65%
- oxygen utilisation by body can never be more than the rate at which cardiovascular system can transport oxygen to tissues
What causes excess O2 consumption?
- resynthesis of PC in muscle
- lactate conversion to glucose
- restoration of muscle and blood oxygen stores
- elevated body temperature
- post-exercise elevation of HR and breathing
- elevated hormones
How is lactate removed after exercise?
classical theory
- majority converted to glucose in lever
recent evidence
- 70% lactate oxidised (substrate by heart and skeletal muscle)
- 20% converted to glucose
- 10% converted to amino acids
lactate removed more rapidly with light exercise in recovery
- optimal intensity is ~30-40% VO2 max
What factors are dependent of diet?
restoration of glycogen and exercise capacity
What are the contractile forces of muscle?
maximal contractile force between 3 and 4kg/cm2 of muscle cross-sectional area
holding strength of a muscle is 40% greater than contractile strength
What is the relationship between muscle work and power?
when muscles contract they produce tractive forces (tension) that act on muscles’ insertions
- isometric, concentric, eccentric
work = f (applied by muscle) x d (over which force is applied)
power = work/time
Describe fast and slow twitch muscle fibres
different categories based on biomechanical and contractile properties
slow twitch = type 1
fast twitch = type 2x and 2a
How do muscles adapt to resistance training?
- muscles that function under no load increase little in strength
- resistance training is conducted to induce changes in muscle size
- hyperplasia (inc in number) or hypertrophy
Explain muscle hypertrophy
- englargement of both type 1 and 2 fibres
- greater hypertrophy in type 2
- inc in myofibrillar proteins
- increases number of cross-bridges
- inc ability to generate force
- resistance training activates satellite cells to divide and fuse with adjacent muscle fibre to inc number of nuclei in fibre
Explain sex differences in body composition
- men have more lean mass, woman have more fat
- testosterone leads men to have larger muscle mass and lwoer body fat %
- normalised to muscle vol, bodyweight or fat free mass, strength difference between male and female athletes are minimal
- women possible ‘less fatiguable’ than men in isometric/concentric muscle actions
What are the unique challenges of para-sport?
- inc value of practitioner input
- limited published data
- heterogeneity
- many sports are unique
- most situations demand interdisciplinary input
What are impairment specific conditions?
amputees
- less surface area for dissipating heat
spinal cord injuries
- limited sweating and blood flow redistribution below lesion
cerebral palsy
- movement inefficiency leading to inc metabolic heat production
multiple sclerosis
- often experience a worsening of symptoms when exposed to heat
other neurological impairments
Why is heat preperation imporatant?
heat stress can come from prolonged passive or active exposure.
without prep, heat can compromise physical and cognitive performance
- reduction in physical capacity
- thermal discomfort
- impaired decision making and skill execution
